Geo 240 Last Test

Sierra Madre fault

"Building the San Gabriel Mountains, one earthquake at a time" - Jet prepulsion Lab built against and ontop that scarp -two earthquakes 20ka total, 6m tall scarp

LA's Urban Fault Hazards:

*Big bend* of the San Andreas red stuff big bend of san andreas , a bunch of east right faults, orientation almost parrallel to relative plate motion, misalignment that creats all of this north south fault convergence-getting big east west rev faults -all vectors parrallel and exactly the same length, increasing is eastic strain accumulation, SA dead parrell to the vectors thats why coast no mountains, angular mis match causes northsouth shortening, creats that extra work and builds mountains the *north south shortening makes the transveres rangeres east west mountains* -Where it stops being parrallel it is at the big bent then back to being parrallel in south -*East west fualts* buidling transvess mountains built above reverse faults, why all these ew faults here bc of this misalighnement, earthquakes on transvese faults built those ranges Channel islands thrust fault ex -San Gabriel Mtns vectors Parrallel and 8 mm a year moving south/right, mountains getting closer to USC 5 mm a year -USC right at boundarie between ew transverse ranges faults and a long RL SA strike slip fault to south -major known faults in LA urban area *Puente hills blind thrust and sierra madre cucamonga fault system* -San Gabriel Mtns are from *Sierra Madre Cucamonga fault*

Notess

*No Earthquakes along the Juan de Fuca* - North American plate boundary subduction mega-thrust because the boundary is locked ***WHEN TWO PLATES CONVERGE TOWARDS EACH OTHER ... AND IF THE INTERFACE BETWEEN THEM IS LOCKED ... THE UPPER PLATE MUST BE BOTH SHORTENED ELASTICALLY (BY BENDING) AND UPLIFTED -During an earthquake, the *elastic strain energy* that has been stored up by relative plate motion since the previous earthquake is released -*Ghost forest* tsunami remnents effecting trees with salt water, As the coast subsided that day, trees found their roots in salty water, -The Basin and Range province of the western United States is a world-famous region of *crustal extension and thinning*. Extension occurs by *displacements along normal faults* that bound the many mountain ranges within the province and that define its western (Sierra Nevada) and eastern (Wasatch Front) boundaries -All of the major population centers along the *Wasatch front NORMAL FAULT, saltlake city is on the hanging wall so in an earthquake it would move down*

3 big blinds thrusts

*Northridge thrust-northiridge e peunte hills thrust- 1987 whitteir; a huge loss of billions in future earthquake compont thrust* -fold is halmark of blind thrust faults, *study them through the folds*, folds trap oil, tar pits oil migrates up until folds sto it, send sound energy into ground - The PHT is a "blind" thrust fault (does not extend all the way up to the Earth's surface)

The Geomagnetic Time Scale

- Idea that magnetic field flips orientation, Important, know the ages of things really cool -*Alan Cox* developed it all point to magnetic north pole, 750 yrs ago turn to south pole, meaning earths magnetic field switches polarity frequently and rapidly • We have a good record of geomagnetic reversals back to about 60 Ma • Based on determining the magnetization of rocks of known age (from both the oceans and the continents)

Why does Earth have a metal core and a rocky mantle and crust?

-Early Earth heats due to radio- active decay, compression, and impacts -This differentiation caused the heavy metals (iron, nickel) to be concentrated in the core of the earth, whereas the light elements (oxygen, silicon, aluminum, potassium, sodium, calcium etc.) were enriched in the mantle. The lightest elements ended up preferentially in the crust -low frequency energy propogates much more effectively and properly longer than normal -changing view of the earths interior structure with change to seismology -inside of earth hot because pressure that happened in the very beginning is hot, all different material boyant flot up and the heavy hotter ones sink making the core, the crust is the least dense materials that floted to the surface 13

dipole

-Earths magnet is a (answer) placed at earth interior; slightly inclined (11°) from rotational axis Magnetic Field Lines Show: 1. magnetic pole not located same position as north pole 2. Earth's magnetic field periodically undergoes polarity reversals, switches 180deg north/south 3. Polarity of magnetic field at given time is recorded (or "frozen") in rocks formed at same time, tells us rock age and magnetic field at that time Earth's Magnetic Field • The field looks like that produced by a dipole located at the center of earth. • The field is inclined with respect to the axis of rotation. • Freely suspended compass needles line up along the magnetic lines of force. • Lines of force are more vertical near the poles and more horizontal near the equator -magnet aint exactly straight, its at the curve a little off from the north pole ab 15 deg

Inside Earth

-Lithosphere, aesthenosphere, and mantle convection: In lithosphere rising magma forms new lithospehere and there is a pulled plate -Pulled plate: Polymorphic phase transformations of ultramafic rocks result in deeper parts of the subducted slab becoming denser than shallower parts, pulling it downward like an anchor Homogeneous Earth: If the Earth were a homogenous ball, ray paths would go out to all ends of circle, ITS NOT A HOMOGENIUS BALL, ray paths in actuall earth blocked out from core inner core solid bc we losing heat since the planet formed, eventually run out from heat of accretion disk, number of seismometers exploded bc of nuclear test ban treaty

Modern Mercalli Scale

-MMI can work reasonably well in some instances (e.g., this MMI map for 1906 SF eq), BUT (a) it doesn't actually measure the size of an eq and (b) it is dependent on many different factors instead of just the seismic rupture - We still use maps of shaking intensity, all now computerized, for rapid response

1857 Mw 7.9 Fort Tejon Earthquake

-Most recent earthquake on Southern slab of SAF? -creeping section with little earthquakes between the northern 1906 Sanfransisco earthquake and the souther 1857 Fort Tejon earthquake

Principal stresses

-Normal stresses acting on planes on which there are no shear stresses Sig 1: max principle stress direction has max compressive normal stress and 0 shear stress, mountain side Sig 3: Perpendicular to sig 1 and is minimum principle stress direction also 0 shear stress, flat side Sig 2: same thing intermediate stress going through diagonal *shear stress comes in through earthquakes with elastic strain energy*-as you go more into west california more of energy

Apparent Polar Wander Curves (1950s

-Paleo-North poles for Europe North America make no sense in their current locations, but track perfectly with one another through time if restored to their 300 Ma Pangea configurations -Yet another strong line of evidence for continental drift. But most people STILL didn't "believe it". So what finally changed their minds 10 years later? - Oldest rocks on Earth; found rock that didn't heat • Acasta Gneiss, northern Canada 3.6-4.0 Ga Carbonaceous Chondrites, those rocks only there when big bang started •But maybe in eastern Greenland? Controversial Oldest mineral grains on Earth; Jack Hills zircons oldest = 4.4 Ga, (Australia) Carbonaceous Chondrites *used carbon dating for most accurate ages* -Half life of decaying for molecules, carbon 14 decays to nitrogen 14 and half life 5,730 yr half life, good for dating, C14 decades to 50,000 years, c14 combines w oxygen forms radioactive CO2, plants mainly breath C12 1% C13 0.00000001% C14, can date bones would charcoal to anything in that rock cycle -*earth 4.6 ga old minerals 4.4 ga old*

notes about inner composition

-carbonacious chondrites tell us bulk composition of earth, about 7000 deg in molt kelvin -how body waves propogate through the earth wth chondrites -as you go from low velocity layer to high velocity layer refracts more parrallel to that boundary -those seismic waves allow us to determine interior structure of earth (re listen to important part) -competition of what gets there faster, wave speeds on the bottom much faster; the *first hint you get from an earthquake is usually the pwave that travels deep*

Isostancy

-everything in floating equilibrium, something high supported with low density, fixed idea that the continents never moved but thought there was vertical motion 19th Cent View: Vertical Motion of Land - The surface of the Earth goes up and down (over long time intervals) due to unknown processes acting deep in the Earth. One part of this was isostasy. Isostatic equilibrium ice berg floats on water mountain float on top mantle

active fault

-fault that has had surface displacement within Holocene time (about the last 11,000 years) -ex Andreas Fault, San Jacinto fault, Hayward fault, Garlock fault

Notessss

-frequency content of radiated seismic energy in 2011 Mw 9.1 Tohoku Japan, Response of tall buildings in Tokyo to long-period waves (high frq waves, in lab today)

Strike or Fault, Dip, Direction of Dip

1. A crack in the rock that has experienced relative motion of the blocks on either side 2. the line of intersection between a plane (e.g., fault, bedding, landslide slip plane) and horizontal surface, measured clockwise from north 3. is perpendicular to the strike, and must be specified (e.g., 30° west)

Paleomagnetism, Fossil magnetic remanence of the rock

1. Earth's past magnetic field as it is recorded in the rocks -Discovered by 2. premise is rock can hold the direction of magnetic field that existed at time and place rock was formed

Source Effects, Directivity Pulse, Path Effects, Site Effects

1. Location 2. Duration 3. Magnitude 4. Frequency content of radiated seismic energy -bigger the quake, more low E frequency release -smaller the quake, more high E release 5. Rupture propagation direction and source directivity -doppler effect on P waves -rupture propagation velocity typically 80-90% of shear wave velocity -need rupture propagation to be parallel to slip direction -almost always happens in large strike slip fault ruptures 1. Plate-scale controls 2. Regional subsurface geology 1. local geology -bedrock vs. weak soil/sediment basins -sediment vs. bedrock shaking -sediment amplification (Vs30)

Why do we want to know what the subsurface looks like?

1. Petroleum companies use images see where oil trapped in folded or faulted rock layers 2. Earthquake geologists use images of subsurface locate faults not visible on surface; blind faults *Northridge thrust-northiridge e peunte hills thrust- 1987 whitteir; a huge loss of billions in future earthquake compont thrust*

Shadow Zones

1. Pwaves inside the earth: The refraction of P waves across the core-mantle boundary (CMB) is the primary observation (together with an understanding of the bulk composition of the Earth from meteorites) that tells us that the core is made of metal -If there is a ray between two deminasional makes a *p wave shadow zone* telling you that the core is completley different than the mantle space for core, no S waves on bottom half of earth 2. Swaves inside the earth: This S-wave shadow zone is what tells us that the outer core is molten -when earthquake is recorded that whole thing is the *S-wave shadow zone*, no primary S waves coming straight from source on other side of earth-shear wave S wave shadow zone cannot travel through liquids tells us outer core is molten

eastern california shear zone earthquakes

1872Mw 7.6 Owens Valley earthquake 1992 Mw 7.3 Landers earthquake 1999 Mw 7.1 Hector mine earthquake -right lateral strike slip faults here These are all examples of major historical??

Death Valley

Formed through a combination of normal and right-lateral strike-slip faulting, also has normal fault scarps -Badwater; lowest point in North America

leaning tower of sanfrancisco

Millenial Tower: leaning down about 18 inches, took cheap route didn't dig in that much like the building next to it to get to more stable bedrock and they gonna have tear it down

Locating an earthquake in 3D with S - P travel times

Need four things: lat, long, depth, and time Step 1: measure S-P travel tiems for multiple stations Step 2: Draw resulting distance radii for at least three stations

1869 Mw 7 Hayward Earthquake

Origional Great San Fran Eq a lot of fill done after the gold rush, would fill in the creeks then put buildings on top and then those buildings would callapse; Clear concentration of damage on filled land -the whole waterfront of sanfrancisco all on filled land, still there because they have a retaining wall that will colapse in huge EQ but looking for money to rebuild bay -*treasure island big island of fill after 1906*, so much stronger shaking with the mud -v of shear waves can't propogate thru liquids and gases

Ventura-Pitas fault system

Ventura-Pitas fault system, part of different fult set could do a mag 8 earthquake, a lot of oil -possible source of Mw8 earthquakes not involving the San Andreas -Ventura fault slip rate based on structural model & VAA terrace ages, 4.1-8.1 mm/yr -Note prominent growth interval (brown) between 5 ka and 3 ka -*Major Transverse Earthquake Hazard*

Aftershock

big earthquakes can generate tens to hundreds of thousands of aftershocks, Aftershock sequences for large earthquakes can last decades before rate of aftershocks finally decays back down to pre-mainshock levels

More eqs and acts

*1971 Mw 6.7 San Fernando eq* -Alqust Priolo special Studies Zone Act -Crippie walle, 2x4, big earthquakes break pipes rate limiting step was the avalialiablity of fresh water -6 months to fix water worst case is a year Great So Califo Shake Out -big eq generate a lot of low freuqnecy and high as energy gets trapped and amplified in sedementary basin -gonna get hit hard by 2M (200cm) veloctity ground motions -gonna break flows that will leave to cascade failures, we steal water from everywhere else, no water left in colorado river storm drains so full of toxic stuff more important to treat than the actual suage -*2.9 m wide elizabth tunnel* goes through the san andreas, if you moved it right it would run into hard rock and its gonna close out, *one solution* is to make it wider than largest displacement, another put in another pipe that will plow into the wall and still have some water during a bad earthquake -sewage pipes and water distribution pipes are gonna break and they might intermingle, key is armoring the infrastructure in advance

Types of steel columns, building materials

-*Brittle concrete Column*: Too little steel allows concrete to break apart, no extra steel top and bottom, less internal steel -*Stronger concrete column*: flexible column more steel reinforcing bars, keep concrete in place during shaking, more steel near top and bottom, throughout column, extra below-2nd square steel bar at bottom at 135 deg -Addition of confining rebar to existing Columns and beams -Modern ductile construction showing extensive confining rebar -90° vs. 135° terminations of confining rebar -Hatussas (modern Turkey), ancient Hittite capital, Ruins of ancient palace -Holes drilled in top and base of stone blocks to hold bronze rods - One of the earliest-known examples of eq-resistant designHatussas (modern Turkey) Los Angeles City Hall 32 Stories, Built 1928: *Tallest Base isolated building in the world*

Important Eqs

-Brick building destroyed during *1868 Mw ~7.0 Hayward Earthquake*, Hayward fault; Failure of buildings built on filled ground, was obvious in this event -Unreinforced masonry gates destroyed during 1906 Mw=8 San Francisco earthquake, San Andreas fault -1933 Mw=6.4 Long Beach Arguably the *Most Important Earthquake in History* - One of Many Elementary schools destroyed during 1933 Mw=6 Long Beach earthquake, Newport-Inglewood fault Led to rapid enactment of the *Field Act: banned the construction of unreinforced masonry buildings* -Offset orange trees, *1940 Mw 7.0 Imperial Valley* eq: The "El Centro record" was the first on-scale recording of near-source strong ground motions in a large earthquake-showing 0.3 g

Current Building Code

-Current building codes are mostly prescriptive rules based on the building type and seismic zone. • Code shave been developed by fixing deficiencies from past earthquakes (e.g., 1933 (brick), 1940 (non-ductile concrete good), 1971 (non-ductile concrete bad), 1994 problem with welds in steel buildings). • If you've got a good building code,who needs a seismologist? • Largemagnitudeearthquakes(i.e.infrequent) may be the primary threat to our societies (e.g., Mw>7 Puente Hills Thrust). Typical wood-frame house construction - Note 3D wooden "skeleton" sheathed in shear-resistant plywood sheets Rancho Cucamonga, CA (in quizlet) -*wood frame* when properly built will ride out the earthquake, more of the damage comes from flying objects

Dead Sea Fualt & Jericho

-Note location of Jericho adjacent to Dead Sea fault, forming prominent alignment of valleys and lakes from upper left to lower right -The actual "Walls of Jericho"Note that they have indeed "tumbled down",but likely not as the result of a trumpet blast!-10,000 years -Dead Sea Fualt and Jericho Megiddo (Har Megiddo) = Armageddon

Andersons Theory of Faulting, Normal Fault, Thrust Fault, Strike Slip Fault

-Relationship between three principal stresses and different types of faults, surface of earth always plane of 0 shear stress, found that faults form at angle 30 deg to max principal stress direction 1.If sig 1 vertical to earth surface, (answer) with dip of 60 2. If sig 1 horizontal and sig 3 vertical (answer) above 30 (below 45) 3. If both sig 1 sig 3 parallel to earth surface, sig 2 is perpendicular and vertical, then (answer) -*elastic strain energy is the energy that drives earthquakes*

San Andreas Fault Info

-San Andreas main strains are san Jacinto and Elsinore, The San Andreas (in red) has, with good reason, long been California's best-known fault (biggest, fastest, largest eqs -The *"Big Bend" of the San Andreas; Misalignment with Pacific-North America plate motion adds extra N-S compression (and big faults that uplift all of our mountains!*)

Snell's Law

-Sin(angle measured from normal)/velocity of ray=constant, sin i/v1=sin r/v1, sin r/v1=sin R/v2 -*Angle of reflection always equals angle of incidence ∠i =∠r* -light travels slower in denser materials, V1 in air greater than V2 in water because water is denser, normally air is most dense so light travels the fastest in air, velocity glass<velocity air

Surface Waves and Dispersion

-Surface wave particle motions die off with depth like water waves. -Longer wavelength surface waves penetrate deeper into the earth than shorter wavelength waves. -Because seismic velocities increase with depth, longer wavelength surface waves travel faster than shorter wavelength waves. This property of the dependence of velocity on wavelength is known as "dispersion" -Because surface waves are dispersed, they arrive at distant stations over a range of times rather than all at once, as in the case of body waves. This leads to the arrival of a "surface wave train" rather than a single pulse or two. -dispersion is the deeper waves going faster ts tp time farther as u go farther away, high freq and different arrival times farther from eq

Principles of Plate Tectonics

-The lithosphere is made up of a mosaic of moving plates - segments of a spherical shell -Plates are rigid except near their boundaries, where relative motions between plates occur -New plate can be created at divergent boundaries and destroyed -At convergent boundaries -Most earthquakes, volcanoes, and mountain building occurs at boundaries between plates -Idea that the outermost part of earth, or lithosphere, made up of twelve large plates that move past each other

Omori's Law

-The number of aftershocks decays exponentionally with time after a mainshock -almost all moderatley large to large earthquakes have aftershocks - *ON TEST on average typically for any mainshock have 1 aftershock 1 w Mw unit smaller, if magnitude 4 typicall biggest after shock 3, then 10 after shocks 2 mw smaller, 100 aftershocks 3 mw units smaller* -deep earthquakes fewer aftershocks

San Fransisco Earthquake (1906), Fort Tejon earthquake (1857), Mission church San Juan Capistrano (1812), Owens Valley Earthquake (1872), Landers Earthquake (1992), Hector Mine Earthquake (1999),Sulwasi Earthquake (2018), 1971 San Fernando Earthquake, 1994 Northridge Earthquake, whittier narrows earthquake(1987)

IMPORTANT EARTHQUAKES TO MEMORIZE 1. 1906 Mw=7.9 from rupture of san andreas, 450 kilo of fault ruptured (150 south 300 north), slip of 6-9m-vast reason san fran was destroyed was because of *fire* that came with it not eartquake-one of largest SA -ground failure was destroyed by earthquake no water pressure to fight the fire, would blow up whole blcks -downplayed destruction of the city to build more-1 largest SA, SAID IT WAS FROM FIRE NOT EARTH QUAKE SO THEY COULD REBUILD MUCH QUICKER 2. 1857 7.9mw, *southern california 350 k and av slip 5 m* 3. December 8/*1812 6.9 mag at a mission church found trees died then and in the winter hit from 1812 and 1857, avg reccurence interval on san andreas 100 years, 161 years since 1906-1 largest SA, would mark it in their church books when wall fell and had to go to mexico for supplies -*Tree related evidence* 4. 1872 7.6 mag, 100 km long maybe 150, magnitude estimates all over the map, 7.6 mag for them , there is a grave for the people who died -Adobe technique of building for walls, doors made of wooden beams and if shaken falls apart, the doorway only thing standing, big percent of lone pine pop killed because of poor structure of earthquake -owens valley fault (right lateral strike slip fualt) runs under scarp of seirra nevada fault (normal fault) 5. 1992 7.3 Mw (Part of Eastern California Shear Zone): RL Strike Slip fault earthquake 6. 1999 7.1 mw, northern part of rupture ripped through u can see its also RL strike slip fault earthquake, have military base around there, had an exactly parallel surface rupture, and mine 7. Mw 7.2 Earthquake: in Indonesia poor buildings hurt -7,2 strike slip fault 2018 sulawesi Mw 7.2 earquake fastest slipping earthquake, things prob underwater landslide generatig from earth, tsunami on pacific rims good predicters could take minutes to get on shore -very fast slip rate, earthquakes don't kill people, buildings do -Left-lateral strike-slip Palu fault (poorly known, but has a very fast slip rate [possibly as fast as ~40 mm/yr! Faster than the SAF!]) 8. 1971 Magnitude 6.7 -only ruptured 10% of seirra madre fault 9. mag 6.7 in 1994 in northridge, 33 killed, 7,000 injured ≈ $50 billion in damages -biggest natural disaster cost in american history before katrina 10. 1987 mag 6.0, happened on peunte hills blind thrust -everything else 7 but sanfransisco, fort tejons, owens, whittier 6

Earthquake damage assesment

-The primary cause of earthquake damage to buildings is the deformation which the building undergoes as a result of the inertial forces acting upon it -reduce earthquake generated forces, base isolation with pads and changing displacement the *inertial forces* which the building undergoes are proportional to the building's *acceleration* during ground motion, building actually tends to vibrate back and forth in varying directions -primary cause of earthquake damage to buildings is the deformation which the building undergoes as a result of the inertial forces acting upon it structures with longer periods of vibration reduce acceleration, while those with shorter periods tend to increase or amplify acceleration

DART II Tsunami system

-The system consists of a seafloor bottom pressure recording (BPR) system capable of detecting tsunamis as small as 1 cm, and a moored surface buoy for real-time communications. -Has two-way communications between the BPR and the Tsunami Warning Center (TWC) using the Iridium commercial satellite communications system. The two-way communications allow the TWCs to set stations in event mode in anticipation of possible tsunamis or retrieve the high-resolution (15-s intervals) data in one-hour blocks for detailed analysis. -The systems transmit standard mode data, containing twenty-four estimated sea-level height observations at 15-minute intervals, once very six hours

Seismic Waves in Earthquake Studies

-Tool to image the subsurface; that is, to "see" below the ground -A seismic source like a 'wacker,' hits ground hard enough sending pulses P-wave energy to ground generating waves reaching seismometers many paths, reflected/refracted based on Vs -Geophones record travel time waves return to surface, used to find V, V=d/t

Seismogram, vertical, horizontal

-a recording of the ground motions at a particular location due to the passage of seismic waves generated by an earthquake. The recording can be make by a single self-contained unit called a seismograph, or by a more complex system of remote detectors, electronic amplifiers, transmission lines, and modern digital computers; basis is idea of pendulim on a screen 1. Vertical seismograph illustrating the principal of the inertial mass 2. Horizontal seismometer in the form of a "garden gate" -The weight with a pen affixed (sometimes called the "inertial mass") tends to remain stationary when the ground shakes. Everything else moves with the ground including the rotating drum. In this way, the pen traces a wiggly line on the rotating - The suspended mass (yellow), sometimes called the "inertial mass", tends to remain stationary during ground shaking, Borehole installation to reduce surface noise *modern electronic wave replaced by heavy magnet*

Liquefaction, liquefaction with earthquakes

-condition of soil and unconsolidated sediments losing their resistance to shearing, water that is located in pore spaces between sand grains is mobilized due to shaking and essentially turns the sediment into a fluid--leads to ground failure in eq 2011 Mw=6.3 Christchurch earthquake Cars partially buried by extrusive sand during 2011 Mw=6.3 Christchurch earthquake -Large areas of the city experienced spectacularly voluminous liquefaction. As many as 10,000 homes may not be rebuilt, as the ground is considered by the government to be too unstable. -1985 Michoacan Mw=8.0 earthquake Liquefaction in Mexico City, 10 to 20 storie buildings collapse matched resonance frequency, sedimentary basin -Collapsed of buildings caused by liquefaction during the 1964 Mw=7.5 Niigata Earthquake

Frequency, High, Low

-large amplitude, low frequency seismic waves are generally the ones that do the most damage, Seismic waves increase in amplitude and become lower in frequency when they travel from bedrock into weaker soils and sediment -Regions with the (Blank) risk of seismic hazard and highest shaking intensities are located in areas of unconsolidated sediment, man-made landfills, and near coastlines and bays, regions with the (blank) seismic hazards and shaking intensities are located in areas composed of bedrock - generally in surrounding hills and mountains -Notice that the regions of highest shaking intensities are located along the fault trace and around coastlines where unconsolidated sediment and artificial fill exist

seismic tomography

-mapping details of interior structure of the earth, based on body waves (P and S) how they behave when they pass through the layers, shapes, details of how much slower or faster mantle is -wave speed depended compossion and pressure and a lot on tempurature; colder it is faster the waves will go, hotter;slower waves -The different "layers" of the Earth (e.g., mantle, crust) are not internally homogeneous. Rather, seismic waves travel at different velocities in different places dependent on a wide range of factors, including composition, pressure (depth) and especially temperature

Crust, Oceanic, Continental, mantle, core

-outside part earth Two types: 1. Ocean, basaltic, denser, crust 100 km thick, subductible, -thin, compositionally different -SiO2, feldspars, tectosilicates -buoyant, low density -isostacy -high variable thickness, avg. 30km but ranges 5-85km 2. Granitic (more silica-rich), thicker, less dense/more buoyant, does not subduct -crust 40km thick -mafic, low Si content, nesosilicates 3. -largest part of Earth by volume -composed of ultramafic rocks -olivine is dominant in upper mantle -ridge push vs. slab pull vs. basal drag theories 4. -iron core accumulation during accretion/differentiation -core accumulation due to gravity (metal pond theory) -heat LOSS from core drives plate tectonics as a cooling system

Path Effect, 1906 Mw 8 San Francisco, Virginia Earthquake Mw 5.8 , 1812 Mw 7.4 New Madrid Missouri earthquake

-path energy is taking, paths exert basic control on how much energy gets to site, depends on geology of that pathway 1. for a long time people thought *1906 Mw 8 San Francisco was 8.3*, vast majority of seismometers in europe, seismic energy released in cali has efficient pathway to europe, *the path effect from cali to euorpe explains that* 2. *Virginia Earthquake Mw 5.8* people felt it all over even in new york and Wisconsin and all over upper east coast, its because newer cold solid rigid land that seismic energy propagates efficiently in spreads out more 3. Relative area of felt shaking from Mw 7.4 New Madrid Missouri earthquake, it is from path effects that they though it was 8.4 they used MMI scale reports of intensity, felt area was enormous, it went up to boston and montreal down to georgey, this energy propogated extremely far, farming on missipi river mud (not coincidence) it amplifies seismic shaking becasue of the amplification of week sediment

isotropic stress, techtonic stress

All tractions pointing inwards towards a point have exactly the same magnitude - stress is same in all directions, so stress ellipse is a perfect sphere -But *inside the Earth*, the strength of the stresses are usually NOT the same in all directions, *stress is an ellipsoid in earth, not a sphere like water* called (answer) -isotropic stress+techtonic stress= total stress

Richter Magnitude, ML

-ripped off astronomy scale, richter just borrowed it L stands for local earthquakes, based on measuring 1 sec S waves on a specific type of seismometer (Wood-Anderson tarsio seismometers) -at an assumed idealized 100km distance from the earthquake (estimated empirically ) -Measurment is the amplitude of the largest S wave on the seismogram (tallest wiggle with a ruler) -based on powers of 10, in mag 1 earthquake the largest S wave measured would be (1/10) as high as for an ML=2 earthquake (assuming the 2 earthquakes were same distance away *richter magnitude does not measure energy released in an earthquake, it measures the amplitude of the largest shear wave on the siesmogram*, *mag 0 from smallest S wave he could measure*---KNOW THIS;there are negative magnitudes -*magnitude scales are theoretically open at both the low end and the high end, theoritically there is no max or min magnitude size which can get lower or larger, unlike the MMI closed scale* -you need the slip to occur at incredibally high velocities before you generate the seismic waves, when faults break they are going from 0 to 100 -largest earthquake ever recorded is 9.5, one could imagine mag 10 but not magnitude 11 not enough fault -smallest earthquake we think is physically possible is prob magnitude -4

Source Directivity Doppler Shift (change in frequency)****** But what about the arrival time of the energy carried by each wave?

-strong rupture directivity during the 1992 Mw 7.3, Landers earthquake 1906 San fran shacking intensity around the coast highest ****Deltas in Book -Derived ground motions in the San Francisco Bay Area and the Delta Region are of considerable importance • High PGV in Santa Rosa Basin • High ground motions out into Delta • Areas of localized highs • Geometrical vs Geologic Effects

2 criteria for directivity pulse

-the *slip direction* needs to be parrallel to the *rupture propogation direction* -You will always generate atleast one deractvity pulse for big strike slip fault -(Puente Hills) blind thrust fault slip direction is parrallel to the dip of the fault, -doppler effect on P waves -rupture propagation velocity typically 80-90% of shear wave velocity -need rupture propagation to be parallel to slip direction -almost always happens in large strike slip fault ruptures (3km velocity)

Teleseism (disant Earthquake)

-the farther you are from the earthquake the more different the gap will be between P,S, raylegh and love waves (surface waves) -For distant earthquakes *surface waves biggest wave phase* (largest amplitude), because surface waves propagate more effectively with distance than body waves do because; 1. body waves spread a sphere, and energy spreads out as 1/r^2 -Surface waves spread in 2d Cylinder, so energy spreads out as 1/r; the distance is less 2. It's frequency dependent, waves lose energy at every cycle -body waves are high frequency; shorter wavelengths and lose energy faster with propogation -Surface waves are lower frequency; lose energy more slowly with distance/so more avaliliable

lithosphere, Oceanic, Continental, asthenosphere

-the strong, rigid outer shell of earth contains crust and uppermost part of mantle -*both oceanic and continentle in NA plate* Two types: 1. Ocean, basaltic, denser, crust 100 km thick, subductible, 2. Granitic (more silica-rich), thicker, less dense/more buoyant, does not subduct -crust 40km thick 2. All plates in the lithosphere move over this, a weak, partially molten part of earth in upper mantle, lithosphere 100km thick

Directivity, 1971 Mw 7 San Fernando/1994 Mw 7 Northridge, 1999 Mw 8 CHiChi Taiwan

1. (Blank)eq occurred on the N- dipping Sierra Madre fault whereas the (blank) eq occurred on a S-dipping blind thrust *fault to the west*there is talking about the class notes about the opposite of downtown *-Northridge earthquake: mainshock nucleated at 20 km, ruptured up the dip of the fault, northridge -since slip direction parrallel to slip of fault and rupture propogation parrallel to rupture there is a directivity pulse -EXAMPLE of strong up dip deractivity pulse, not hitting Downtown went 180 deg away since opp direction, not gonna hit USC in puente hills* 2. this earthquake, ruptured almost 90 kilo, *Big Earthquake with no Directivity Pulse Hurting buildings* -there was no deractivity pulse -surface rupturing thrust fault up to 9 meters of slip -*since slip direction and rupture propogation direction not parrallel to each other there is no deractivity pulse, they were PERPENDICULAR -in order for deractivity pulse need rupture prop direction be parrallel to slip*

Earthquake prediction:

1. *A Valid Earthquake Prediciton* Time {Long term = 10 - 100 years Intermediate term = 1 - 10 years Short term = days - months Immediate = minutes Probability • The smaller the uncertainty in each category, the more useful the prediction. • Valid prediction must have less uncertainty than the null hypothesis 2. *Approaches to Prediction*: -Physical Precursors; Based on Dilatancy-Diffusion -Seismicity: Based soley on past seismicity (historical and paleo.) -Cycles: Pattern recogintion Based on stress transfer: Changes in probability associated with each event 3. *Physical/deterministic methods* - Based on search for precursors: -some prior behavior "determines" that the event (e.g., and) earthquake will inevitably follow Statistical/Probabilistic methods - Based on previous history of the system: -If I know how the system has behaved in the past, I can use those data to predict how it will probably behave in the future -Measure recurrence intervals and slip rates of faults: Do the statistics to determine the probability of future recurrence -Potential Problems: highly variable slip rates

Intensity, MMI Scale, Intensity vs Magnitude

1. -Measure of degree of ground shaking at certain location during earthquake, decreases at distances further from epicenter, depends location relative to the hypocenter -Isoseismal map contoured map; given contour shows regions equal intensity of shaking, -Isoseismal lines, separate regions of different intensities, where they all intersect hypocent 2. Closed intensity scale measuring intensity from I (small) to XII (disaster) 1: no movement **** 3: can't feel indoors 5: almost everyone feels it 6: everyone feels it **** 7: difficulty driving 9: really bad damage *** 12: apocalyptic **** 3. -Magnitude measures the size or the* total energy release* of an earthquake, while intensity measures the *degree of ground shaking* at a given point due to an earthquake -Earthquake has *one magnitude*, and *multiple intensities* - Magnitude is an *open scale* logarithm of amplitude of motion range from -Infinity to +infinity normally 0 to 9 havent seen anything higher than 9.5, intensity *closed scale*

A Tsunami Earthquake result of 2 things, 1946 Tsunami 8 Hilo Hawaii

1. Up to 50 m of slip locally 2. Very large displacement right up to the seafloor=tsunami earthquake -These are rayleigh waves Type of tsunami: Generated by the earthquake in Aleutian subduction zone, struck Hawaii with no warning Extras -oceanic megathrust quakes -deep ocean landslides -large-scale water displacement -seafloor surface rupture is effective at raising seafloor -slip amount 10 m *ocean waves driving force wind and gravity, tsunami waves driving force ocean floor*

Hooke's Law, Young's Modulus (Y), Bulk Modulus (k), Shear Modulus (M)

1. -distortion (strain) is proportional to the applied stress -linear stress to strain relationship Three elastic Moduli; -distortion/strain will disappear after applied stress is removed -material will resort to original size and shape if 2. -defines relationship of a specific material to an applied stress -Linear Elastic Strain -Hooke's Law -the larger Y is, the less the material will be distorted 3. -measure of resistance of material to changes in volume, due to pressure or isotropic stress -also called rigidity or incompressibility -think about a tennis ball vs. shotput and response to isotropic stress 4. -resistance of a material to change in shape -gases and liquids have a M=0, which is why S waves cannot travel through them

S-P travel time curves, Local Eqs, Distant Quakes

1. -local: # will be small -teleseism: # will be big surface waves largest amp for these teleseism quakes -for teleseisms, seismic energy usually coming from directly underneath the station, so P waves will be prominently displayed 2. S waves biggest 3. -teleseisms -surface waves will be biggest -body waves lose energy faster with distance than surface waves by 1/r2 -body waves are high frequency and lose energy with distance -LOW FREQUENCY WAVES LOSE ENERGY SLOWER THAN HIGH FREQUENCY WAVES

Seismic Waves, amplitude, Frequency, period, wavelength, velocity

1. -propagation of movement/motion through rock; waves of energy that travel through earth's layers -3km/sec average 2. -height from crest (or trough) to middle average 3. -number of waves that pass in a unit of time ie: cycles per second 4. -time between wave crests passing a certain point 5. -distance from crest to crest (or any relative part of wave) 6. tsunami velocity = 800km/hr -Driven by elasticity of rocks (and metals in core), waves spreading out of a pond go outwards in circle, waves spreading from earthquake blocked by core -Travel through the entire body of the Earth P (primary, pressure) vs. S (shear, secondary)

Earthquakes and Shocks, 1957 Mw 7 Haicheng Earthquake, 1976 Mw 8 Tangshan earthquake

1. 1957Earthquake 7 strike slip, may be the only earthquake predicted by a government agency*, started experiencing hundreds of little earthuqakes, people self evacuated, local official sad sleep outside earthquake impending -predicted based on all of the foreshocks 1976 *Mw 7.8 city near it*, biggest death tole, miners survived, city people died , the official death tole was 250,000 others estimated 750,000; city was completely distroyed, NO FORESHOCKS, no warnings like most *1992 Mw 6.1 Joshua Tree earthquakes*: a lot of fore shocks and aftershocks, saying that was a foreshock to the *1992 7.3 landers earthquake* -next to it in the same morning, not connected to other faults was the *1992 6.3 big bear* *earthquake: definition of aftershock by landers saying triggered earthquake not aftershock even though it is an aftershock* -aftershock sequence for Landers Eq still doing harms

Divergent plate boundaries, Mid-Ocean ridges, decompression melting, Rift stages, Danakil Depression

1. Plates move away from each other, tensional stress, normal faults 2. Two bodies of rock move away from each other, resulting in hole filled by magma through volcanoes forming new oceanic crust, happens at ocean basins called (answer) -Age of crust at ridge=0, move away gets older, mainly in oceans but happens on continents, -Major Oceanic Spreading centers: Mid Atlantic Ridge, East Pacific Rise, Indian Ocean ridge systemMid Atlantic, new crust made, lake balail siberiaia 3. Decrease in pressure on very hot but solid magma upwelling beneath the rift causes it to melt -once established, oceanic spreading centers tend to erupt low-viscosity basalt material -*Pillow Lavas* happens when lava erupts underwater 4. Upwelling, rift valley, sea, ocean (look at slides), red sea/east African rift system 5. An as-yet unflooded down-dropped block associated with rifting and opening of the Red Sea

Seismic Observatory

1. Records entire frequency range, record both high and low frequency earthuqakes -from high frquency body waves, low frequency surface waves 2. records 3 d ground motions; vertical, N-S horizontal, and E-W horizontal -Recording drum time important for seismometers, if drum moves records traces -all the pwave noise with seismology -modern siesmometers have magnets

hotspots, Hot Spot Reference frame

1. Regions of volcanic activity in interior of lithospheric plate, away from plate boundaries or major faults, formed above hot plumes of magma from mantle that rise toward earth's surface -plate over hotspot moves, new volcanoes form, older (volcanically inactive) further away from hot spot younger (active) towards hotspot -persists millions of years 2. Positions of hot spot tracks predicted by model in which they are fixed wrt each other match observations There are three main places where volcanoes originate: Hot spots, Divergent plate boundaries (such as rifts and mid-ocean ridges), and. Convergent plate boundaries (subduction zones)

Convergent plate boundaries, Subduction for OO and OC, Trench, Wadati-Benioff zone, Island Arcs and Continental Arcs,

1. Two plates collide with one another, compressional stresses and reverse faults/thrust faults - three kinds; ocean-ocean, ocean-continent, and continent-continent 2. For OO and OC, denser crust sinks below less dense crust in a subduction zone -In Ocean-Ocean cooler older Oceanic crust subducted beneath warm younger buoyant Oceanic crust For Ocean-Continet; Oceanic crust is denser is subducted beneath Continental crust, ex andes -*For continent continent collision they both push up and create mountains; himylays, alps, when continent continent they dont call it subduction*, also both push down into mantle--taiwan 3. Structures at Subduction Zones: A. (deep depression) will form parallel to subduction zone, deepest parts ocean floor B. earthquakes occur (surface to -700km blow earth) at this boundary between the subducting and overriding plate - inclined belt of earthquakes that defines the top of a subducting lithospheric slab C. Magma is formed as Oceanic plate subducts, rises creating (answer) ocean-ocean and (answer) ocean-continent; chains of volcanoes in oceanic basins or continents (beneath crust in form mtns)

transform plate boundaries, Fracture Zones

1. Two plates move past another horizontally, from large shear stresses making strike-slip faults 2. only the section of the transform fault between the spreading ridge segments is active. The older, inactive parts outside of the spreading ridge are called (answer) -San Andreas all right later strike-slip faults, northern atolian fault August 17, 1999 earthquake in Turkey, newport inglewood fault 1993 long beach

2004 Sumatra Mw 9 earthquake

250,000 killed, started big tsunami in Thailand - First wave arrives, Koh Raya, Phuket, Thailand, December 26, part of basin/harbor ripped to shreds, Banda Ache was shredded, extent of flooding, Mosque there got destroyed - The lack of an early-warning system in the Indian Ocean resulted in tens of thousands of fatalities that could have been prevented during the 2004 tsunami

Site Effects, *1989 M 6.9 Loma Prieta Eq*

1. control on how spot is going to shake right on the geological spot below site, one side of street over another 2. -knocked on sabrinas door and earhquake started, rurally not that bad, but hit downtown very hard -freind in different area standing on something else got thrown -a lot of fires from local gas pipes -here we see the site effect: he was standing on bedrock (less likely liquifaction) while his freind was standing on sand (ensuing liquefaction and amplification) -*week sediments amplify strong ground shaking* MMI not linear -there was a damage cluster in Northern tip of San fran more than 100 km away because the marina up there was made of filled land like the deltas (making it man made bad and week sediment), they *used 1906 rubble to build that neighborhood, building built on fixed land collapse big damage in the marina district that had a lot of fill* -*The foundation for the bay bridge was sitting on mud and poles (week sedimetn) 5 feet of depth built on wood piles and part of it collapsed, in 1989 M 6.9 Loma Prieta Eq*, spent billions of dollars to fix it for next earthquake; putting part of it on good bedrock

Compositional layers, mechanical layers

1. crust (0-100km out of silicates) mantle (100-2900km out of iron and magnesim silicates) core (2900km to 6370 metals iron nickel) -crust itself is 30km 2. mechanical layers Lithosphere, aesthenosphere (100-200km), Outer core-inner core (2900km) mesosphere (stronger than asth), outer core (only part of earth all liquid), mechanical

Reflection Seismology, Seismic reflection survey

1. exploration method using seismology discover/estimate properties of earth's subsurface by using reflected seismic waves 2. Geophysical survey using reflection seismology -P waves are compression waves and can transmit in solids and liquids, S waves are shear waves and can only transmit in solids, P waves travel 60% faster than S waves at earth because they put force in the direction they propogate. S waves travel slower because their force is perpendicular to direction of propogation of wave -P-wave arrival time, tP, generally clear easy to identify -S-wave arrival time, tS, less obvious, usually some P-wave energy at time of S-wave arrival,

stress, normal stress, shear stress

1. force per un area, measured in newtons psquare meter, variation of stresses cause earthquakes/faults 2. stress acting perpendicular or 90deg to a plane 3. stress acting parallel to a plane -if shear stress greater than normal*friction u have and earthquake

epicenter, hypocenter (focus), Origin time

1. point at surface above hypocenter 2. place where the earthquake rupture begins, approximate location of the initial break of a large earthquake 3. time that the earthquake rupture begins

Seismogram, Seismic Stations

1. recording of ground motion at a seismic station during some time period, measured in displacement, velocity, acceleration; recorded digitally with gps signals for timing -Accurate timing of P- and S-wave arrivals tells us how far the hypocenter is from the station -uses Universal time or Greenwich mean time 2. latitude, longitude, in history file, along with location, maintenance, operation -HIGH QUALITY global seismic network, SIMPLER regional seismic station networks -Local and special-purpose seismic networks; Los Angeles Basin, Mt. St Helens

Elastic rebound theory, oracle of delphi and earthquakes

1. storage of elastic strain energy in rocks; GPS-Documenting relative plate motion in real time 2. people getting high at this near hot springs near by, people gettin high

paleoseismology, cross cutting relations, recurrence interval

1. study of ancient (paleo-) earthquakes (-seismology) -earthquakes that rupture leave record of their movement -- fault scarp, digin find earlier erthqks -*strata* rock layers, oldest layers at bottom youngest at top 2. -if layer cut by fault, layer older than that fault, if layer on top not cut by fault older than layer -age of fault rupture between previous and before, trench wall dug to find these, C14 absolute 3. paleoseismic data predictive tool for future earthquakes, (answer) represents the average time between each earthquake, new year minus previous year and find averages

2011 Tohoku Japan Mw 9.0

18,000 killed -Japan was struck by a magnitude 9.0 earthquake off its northeastern coast in March 2011. This is the largest historical earthquake that Japan has ever experienced. In downtown Tokyo, large buildings shook violently and USGS there is severe flooding due to a tsunami generated by the earthquake. - Part of houses swallowed by tsunami burn in Sendai, Miyagi Prefecture (state) after Japan was struck by a strong earthquake off its northeastern coast - The tsunami waves traveled far inland, the wave of debris racing across the farmland, carrying boats and houses with it. -Much of Japan's coast was already protected by high tsunami walls -Additionally, a number of fires broke out including one at an oil refinery which is shown burning out of control -earthquake was the result of thrust faulting along or near the convergent plate boundary where the Pacific Plate subducts beneath Japan -Thrusting of Eurasion and Pacific plate: rate of convergence at this plate boundary is about 90 mm/yr (9 cm/year). This is a fairly high convergence rate and this subduction zone is very seismically active -Pacific plate thrusts underneath Japan at the Japan Trench, and dips to the west beneath Eurasia, Pacific plate moves velocity of 83 mm/yr

Alfred Wegener (1912 continental Drift)

1912, (Answer) (meteorologist and glaciologist NOT GEOLOGIST) proposed that several continents now separated by major ocean basins had been much closer together about 250 million years ago and had been part of a single super- continent called Pangaea - also means that 250 million years ago there was one super-ocean—Panthalassa -In addition to the compelling polar ice cap data, showed the distribution of 300 Ma deserts and swamps, fossil evidence -Dutoit brought in idea of Gondwanaland(Southern Continents) and Laurasia (Northern Continents) -*Continental Drift* deemed to be wrong because said movement through moon wrong *Holmes* 1929 explanation for drifts with slap pull concept but no one listened

earthquakes by urban faults

1971 Mw 6.7 San Fernando 1994 Mw 6.7 Northridge These are all examples of major historical?

curie point, acculmulating

2 ways direction becomes frozen into the rocks: 1. Rock is formed to the (answer) (580°C), above not magnetized, below wrong parrallel direction-stripes ocean floor 2. Sediments (answer) on lake/seafloor particles align with magnetic field at time

divergent, convergent, transform

3 types of Plate boundaries 1. Plates move apart and create new lithosphere (Normal Faults) 2. Plates collide and one is pulled into mantle and recycled, they have subduction zones (Reverse/thrust faults (30deg)) 3. Plates slide horizontally past each other (Strike-slip faults)

Evidence Confirming Paleomagnetism and Continental drift

Columbia River Basaltic Lava Flows: Long-term record of Earth's paleomagnetic field orientation -the developing of radioactive decay gave us dates for earths minerals -- Magnetic reversals in a sequence of lavas of varying age; can look at age of rocks with corresponding magnetic force during the time

Bad Building Styles

Column Beam Failures: *Nonductle concrete buildings*: vertical comlumns horizontal beams, 1. Indadequate strength of column to beam connections, Focuses enormous stress at those column to bean connections will only work if stay at 90 degrees, one failure is the failure to column to beam connections 2. Columns exploited outward from inadequate confinement, The Columns themselves also fail, the shear resistance is the shear skeletal inside, not enough ductility to support building after concrete cracks -izmit turkey might colaspe difference in bedrock *confinement* is a second set of rebar that is wrapped around the vertical rebar to keep it more vertical -a building was straight concrete completely illegal and killed so many people-from the sand in the beach in turkey freshed water that had salt water not good for building -concrete is a combo of 2 things: sement and agrigate, mixture of sand and sement 1988 mw 6.9 Armenia Earthquake crazy off algorithim because of horrible building design--used soviet style buildings with L brackets connecting beams to walls LA picture in hanging wall of puente hills blind thrust fault upwards of (about 1500) 2000 buildings in LA that are not ductile in LA 28 years to fix these buildings *soft first floor construnction*: no shear resistance in structure of ground floor at all -wood frame soft first floor structuer like 7 yrs to retrofit Better: *modern ductle comlumn to building*, connection, more ductile and mpre steal, addition of confiing showing extensive rebar, should look like lots of steel -thicker rebar, a lot, much more 3D integration of vertical and horizontal rebar

Magnitude Matters!

Comparisons with Bay Area scenario earthquakes illustrate extent of 1906 ground motions and indicate high but more localized shaking for smaller events 1906 San Francisco Earthquake (M7.8), Hayward Fault Scenario Event (M7.1), highest intensity neer the shores with barren land where amplified the highest -san fran was NOT hit by strong reactivity pulse in 1906 earthquake, it does but energy, the directivity exerts 0 effection how ground distribution affected Duration: 1964 Mw 9.2 Alaska earthquake

Normal Fault, Reverse fault (/thrust), strike-slip fault, oblique-slip fault

Different types of Faults: 1. caused by tensional forces that stretch rock and pull apart -Horizontally extends the crust, *only divergent one*, rifting/seafloor spreading -Foot wall is left, fault plane is in middle thing, hanging wall is right for normal - (top side) *Hanging wall slips down* relative to foot wall (bottom side -found at rift zones and mid ocean ridges *L final>Linitial*, *becomes bigger* 2. caused by compressive forces squeeze/shorten rock, *convergent* builds mtns -Hanging wall *slips up* relative to foot wall -found at continent-continent collisions or subduction zones -thrust faults, type of referse fault, low angle reverse fault with a dip of less than 45 Degrees, materhorn -Megathrusts in oceanic trenches, subduction megathrusts in convergent plateboundaries, NEAREST Faust pointte hills thrust (25 deg) *L final<L initial, becomes smaller* 3. From shear stresses blocks moving past each other horizontally (NOT UP AND DOWN), San Andreas example, *transform plate boundary* -*Right Lateral*: occurs when one plate moves right relative to another plate -*Left Lateral*: occurs when one plate moves to left relative of other plate *dip of 90 degrees* 4. fault, where there are components of both strike-slip and dip slip (either normal or reverse), so move horizontally past another, and move left and right (up and down)

Nuclear Test Ban Treaty of 1963

Early tests were above ground or in atmosphere, Later tests were underground. Less dangerous for environment, origionally for bombs then used for earthquakes -US and other countries testing hydrogen bombs making fallout, deposited where ever the wind takes them, treaty said no more above ground or atmospheric testing, said future tests below ground or in cave -*earthquakes release most energy at shear wave fase*, -*explosions are purley compressional, huge p waves*, can distinguish difference with seismographs, so early seismographs because of this treaty

P waves, S waves, Surface waves

Earth components is 3-dimentional, measuring 3 types of motion; *up down or vertical, north south motion, and east west motion*, motion in each direction is recorded by the corresponding component of the seismometer -*(blank) waves vertical component, (blank) waves horizontal component, (blank) waves all three*

Fault Fling

Earthquake Triggered Landslides: 2008 Mw 8 Wenchuan Eq; landslide- created dam -Ridge-Top Shattering (ridge rents): Lidar from along the western Awatere fault, New Zealand Fault Fling: 1971 Mw 7 San Fernando Eq-with fault fling fault pops up making an asphalt slab

1906 San Francisco Mw=8, 1857 Fort Tejon Earthquake Mw=8, 1994 Northride: Mw=7, 1960 Chile earthquake Mw=9.5, 1964 Mw 9.3 Alaska Earthquake, Number 3 sumatra 9.2 2004, 1995 Kobe Japan earthquake, 1999 Izmit Turkey earthquake

Earthquakes 1. Mw=7.9 -450km long by 15 km deep -why did the earthquakes rupture down 15 km, it means after 15 km its too hot down there 2. for a mag 8ish earthquake rupture 5,000 square kilometers and avg slip about 5 meters, 1857 Mw=7.9 3. Mw=6.7 -350 km2, avg slip=1.5m 4. *like 100% of really big on subduction megathrust*, Mw 9.5 -down dip fault dip is 15km, *any strike slip fault down dip is 15km* KNOW THIS -subduction megathrust can go down to 30 or 40, about 10deg of dip on sub megathrust, down dip width can be up to 100 to 150 km -*dominant control of the magnitude about the slip and rupture area* -150,000 sq km dip -generated a huge tsunami in hawaii *How much slip occur in a really big one (subduction megathrust) avg slip in 1960 chill was over 30 meters* 5. 1964 Mw 9.3 Alaska Earthquake: Second Biggest earthquake 6. Number 3 sumatra 9.2 2004, thous 3 a lot of energy 7. 1995 Kobe Japan earthquake, Mw=6.9, Mj 7.2 8. Mw=7.6, they said in news Magnitude was 7.8 but Ms was 7.8, Mw 7.6 -turkish used Md or duration scale; based on duration of shaking at a spot, too many parameters and turkey though it was a 6.7 -All of those magnitudes correct for measurement

Direct Wave, Reflected Wave, Refracted Wave

Energy can travel from the source to the receiver over three different ray path 1. in sedimentary layer 1, straight line from origin travel time curve 2. distance 2 times sed layer, comes in middle y axis as hyperbola, most of time is slower can't go through 3. angle of refraction calculated with snells law, refracted wave forms straight line slope equals 1/V2, refracted wave is fastest because it can passs through layer with faster velocity and come back up unlike reflected wave Refracted waves are faster travel through the V2 bottom layer boundary, unlike the others that stay in V1 and are slower. It spends less time in the top layer, and even though it is a longer path it goes faster in V2

90 degree, 135 degrees, 10 degrees

Important degrees for Building Codes: 1. blank degree column to beam connection; most important in dictating whether or not a building will hold 2. ideal crimping angle for confinement rebar 3. if a column exceeds _____, it is unable to resist gravity

paradigm

In science, and all-encompassing idea or set of practices that define a scientific discipline

Earthquake cost of washington subduction zone

January 26, 1700 It occurred off of the coast of Washington on the subduction zone interface between Juan de Fuca plate and the North American plate. The Mw ~9. Evidence comes from: Ghost forests, tsunami deposits and recordings of the Tsunami that were made in Japan

metrics

KNOW THIS! 1 km = 1000m = 100,000 cm = 1,000,000 mm, 1 foot = 0.3048 m, 1mL=1 cm3, 1 inch = 2.54 cm 1 mile = 1609m 1L= 1000 cm3 mass=g, rate = distance/time m=D/V 1 Inch=25 milimeters 1.6 mile in kilo 0.6 kilo in 1 mile ka=thousands, ma=millions, ga=billions

SA plates

Knowing landscapes topographic and geometric maps -Ab 80ma NA plate broke from European plate where we see sierra Nevada, *faralon plate subducted and consumed under northamerican plate* and we got these mountainsns (reverse fault), subducted then rose to be accreted against NA plate for mountains *San Andreas transform* fault (strike slip) 28 ma with collision of Pacific Plate and NA plate, pacific plate moved northwest relative to pacific plate making it *right lateral strike slip* -It's a fault zone of a bunch of faults, pulverized rock called *gougue* found inside

Lidar and Radar

LIDAR = LIght Detection And Ranging RADAR = RAdio Detection And Ranging -And geologists use LIDAR to look through groundcover and see the surface of the earth!

Scarp, Sag ponds, rupture surface, Fault trace

Landscapes in Fault Zones: 1. is features with dipslip (normal or reverse) faults with vertical offset, seen more in normal faults 2. closed depressions of internal drainage found in fault zones if fault bends or sidesteps making echelon fractures, bend in *San Andreas* could give it 3. where failure of rock occurs also called fault surface, An asperity is an area on a fault that is stuck. The earthquake rupture usually begins here 4.line intersecting fault surface and earth surface

Notes

Local Earthquake (within km): -in the closest ones shear waves is the biggest wave face knocks down buildings (S waves largest), slow start of pwaves, then huge strt of S waves -every slip earthwuake generating pwaves swaves love and rayliegh waves, s waves biggest wave phase -For local S shear waves biggest waves

Inclination, Declination

Magnetic Feild Measurements: 1. the angle between the magnetic field vector and the surface of the earth, angle between lines of magnetic flux and horizontal -90 deg at north pole 90deg south pole, at equator 0 deg, if in the middle can calculate it, increases as it goes to both north and south poles till getting to 90 -just need inclination for paleolatitude rock 2. angle between magnetic north and true north at a point on earth's surface, angle between the horizontal component of the magnetic field vector and geographic north -once you direction (I and d) you can find magnetic paleolatitude and location of paleomagnetic pole (with q and d) at that time, 1 deg=111km;large dist use degrees

Richter Scale (ML), Surface Wave Magnitude (Ms), Moment Magnitude (Mw), Japanese Magnitude Scale (Mj)

Magnitude Scales 1. Does body was P and S ML local -theoretically an open scale -1930s CalTech -measures amplitude of seismic waves on a specific type of seismometer, Seismic wave amplitude of mag 6 earthquake about 10 times mag 5 earthquake -Wood-Anderson Torsion Seismometer -calibrated to 1s period of shear waves at 100km distance -scale ranges from -4 to 10 2. Magnitude better for farther -for Ml greater than 7 -based on measurement of 20s or 40s surface waves 3. -energy released in quake -NOT based on measuring amplitude in seismograms -based on measuring entire frequency range of seismic energy released -based on measuring a torque called "Seismic Moment" (Mo) -Mw increases 32x for every unit increase -most earthquakes measured by moment magnitude 4. Mj=Japanese magnitude scale, Mj was 7.2, also Mw 6.9 earthquake, for 1995 Kobe earthquake

Richter scale, Local Magnitude, Surface Magnitude

Magnitudes 1. logarithmic scale, assesses earthquake sizes by powers, uses enormous range -Seismic wave amplitude of mag 6 earthquake about 10 times mag 5 earthquake -was first used for local earthquakes, ML 2. Logarithm of max seismic body wave amplitude (in thousandths of a mm) recorded on standard type seismograph, at distance 100 km from the epicenter -If different instrument or closer or farther than 100km corrections made 3. Best for distant earthquakes (>2000km) surface stronger best -Magnitudes are sometimes determined from either the P-waves (called Body Wave Magnitude, mb) or the surface waves (called Surface Wave Magnitude, MS), or both, depending on the epicentral distance, *Body wave magnitude is Mb*

Blind Fault

Puente Hills Blind Thrust, Northridge blind thrust, Whittier narrows blind thrust -only rupture in the subsurface, never offsetting rocks earth's surface, doesn't produce fault trace or line of intersection between fault surface earth surface; blind fault folding -Blind faults "deform" rock layers at the surface; folding/deform use infer location & orientation -Recency of faulting based on young reformed layers, studied through the folds

California faults THINGS TO KNOW

San Andreas long term avg rate pacific plate moves past the North American Plate , answer is 50 milimiteters a year or 2 inches a year --elastic energy gets stored and unstored, biggest fault and fastest stores elastic strain energy much more than any other plate boundary, system all right lateral strikeslip faults-produces biggest energy -*eastern shear zone* right lateral strike slip faults the sand andreas system 70% and strands 35 mm movement year, 5% on basin and range, and about 25% of the eastern california shear zone fault -50 mm movement -creeping section most abundant little earthquakes

Sand Volcanoes

Sand boils or blank occur when water under pressure wells up through a bed of sand. The water looks like it is "boiling" up from the bed of sand, hence the name 2 Things for it to occur through liquefaction: 1. grain size of the sand must relatively fine, have sufficient space so water can percolate through substrate 2. sand must not be held together by clay residue from overlying soils -Sand Volcano 1979 Mw=6.5 earthquake, Imperial Valley, CA -Sand Volcano 1976 Mw=7.5 Guatamala earthquake -Sand Volcano 1906 Mw=7.9 SF earthquake, near Watsonville, CA -Sand Volcano 1994 Mw=6.7 Northridge earthquake, on floor of former Van Norman Reservoir

Eastern California Shear Zone

Serpentine: California's State mineral (serpentinite is the state rock); Talc is an especially slippery serpentine-like mineral -)Eastern California shear zone* on the right of the san andreas strike slip faults GPS site velocities show Pacific-North America relative plate motion; shows most of the elastic strain energy going to the left where the san andreas is -Eastern California Shear Zone accommodates mostly right- lateral strike-slip on a 100- km-wide zone of ~N-striking faults

Mainshock, foreshock, aftershock

Shocks 1. largest magnitude earthquake in a sequence 2. smaller magnitude earthquake that preceeds a main shock, alway smaller than mainshock, approx same location 3. eqs that are smaller than the mainshock that occur near the mainshock (within 2 rupture lengths of the mainshock rupture), at a rate of occurance higher than before the main shock *95% of the time Southern california has no forshock, meaning in Southern CA if you feel something 5% chance its a forshock to a later larger mainshock;tiny or a lot larger -that doest mean there wont be a big earthquake happening* -likelihood of that feeling being realy realy big is fraction of .5% -*2010 Mw=7.1 Darfield the main shock was vs. 2011 Mw=6.3 Christchurch eqs was the aftershock*

Sacramento-San Joaquin River Delta

Simulations suggest that the San Francisco Bay Area and Delta Region would suffer very strong ground motions during a M7.8 event initiating on the northern part of the San Andreas fault -the levies is what happens and they could fail with all the week sediment from it from fill, and amplifys chances of greater intensity during earthquake

Angle of Incidence vs. Angle of Refraction

Sin R increases as R increases, greater/smaller <i -Larger velocity corresponds to larger angle R (refraction), smaller velocity to smaller angle R -When Seismic body waves encounter boundary, refract according to snell's law with no dependency or frequency/wavelength -High frequency short wave waves refract at same angle as low frequency long wavelength waves; it's a double refraction in prisms, reflect and refract all over for fish bowls

Earthquake

Sudden slippage of the rocks on either side of a fault past each other at a velocity that is fast enough (km/sec) to generate seismic waves - Earthquake Belts Define the Edges of Tectonic Plates - Earthquakes and volcanoes in the Pacific outline the boundaries between plates

Ventura-Pitas Fault System

Tsunami risk from large displacement structures of the BLANK fault system: (1) Very large displacements of seafloor (2) Very near coast (3) Relatively shallow water depths

Body waves, P waves, S waves, Surface Waves, Love waves, Rayleigh waves

Types of Earthquake Waves: on seismograph first p then s then Surface waves A. Curved lines 1. compressional waves, straight -Travel at speeds of 6-8 km/s through the earth's interior. Particle motion is parallel to direction of propagation. Also called primary waves. Similar to sound waves. -Pass through solids, liquids, and gasses -rich in high frequency energy --the first p wave seen on seismogram coming almost straight up,being parrallel to the ray path, p waves well recorded on vertical 60% faster -*Vp= root (k+4/3M)/(P)density* 2. shear waves, wavy; carry most energy in local earthquake and biggest waves -Travel at speeds of 3-5 km/s through the earth's interior. Particle motion is perpendicular to direction of propagation. Also called secondary waves (thus the S). Do not pass through liquids or gasses, only solids *Vs= root M/(P)density* B. (Straight lines)Travel at speeds less than 3-4 km/s. They consist of dispersed wave trains (different frequencies travel at different velocities) that travel around the earth at its surface -ocean wave has prograde elliptical motion, die off with depth -biggest waves for distant earthquakes 1. Particle motion is horizontal and perpendicular to the direction of propagation. SH waves trapped in low-velocity surface layer (e.g., the crust) -particle motion is driven by elasticity; if wave coming behind you it hits you and you snap back, the motion is backwards from the ocean wave, wont be on the vertical -*-horizontally polarized shear waves (Sh) that are trapped in a low velocity layer by total internal reflection (in the crust) -near surface of Earth -what lead to total internal reflection concept* 2. Particle motion is retrograde elliptical in direction of propagation (wavy up and down) -It is a type of shear wave but not a body wave a surface wave -will be on vertical and horizontal components

Uniform California Earthquake Rupture Forecast:

UCERF 3 -3 D perspective view of likelihood each region of CA experience mag 7 or large eq in next 30 years; duration of homeowners mortgage -smaller eqs do pose greater threats; 62% prob of eqs

Pacific Ring of Fire

belt of volcanoes and large- magnitude earthquakes around the rim of the Pacific, johnny cash song Why are there volcanoes along subduction zones? -As slab descends into aesthenosphere, fluids and gases are released from the subducting rocks. These rise and cause melting of the overlying rocks (again, hot but solid if dry). This magma then rises to the surface where it is erupted. - Subducting volcanoes explode because ascending magma rises through silica-rich continental or island arc lithosphere, Ex Nuee Ardentes -most damaging earthquakes and most large tsunamis occur around Pacific rim Iceland: Coincidence of a Hot Spot and Oceanic Spreading Ridge; rifting and seafloor spreading, with NA plate and eurasian plate

Paragdim Shift in the 1960s

big shift in acceptence The Most Convincing Evidence Came From the Study of Paleomagnetism: (the record of the Earth's past magnetic field locked into and recorded by the rocks) - Motions in the molten outer core generate Earth's magnetic field (good thing, too! Saves us from meteors hitting us 500 m/s, Earth's dipole magnetic field is like a bar magnet (except in 3D -founded

Stick slip surface vs deep surface, volume reduction hypothesis deep earthquake occurence

fault moves stops and goes again 700km stickslip, stick if not moving slip when it slips, causes shallow -volume reduction hypothesis they think its from some minerals that they suddenly change volume because there structure has changed making seismic waves

Predictions from Class

richter quote predicting earthquakes: crazy to predict -doesn't think ever gonna get to that stage when can predict earthquakes -tried to be like we'll predict it like weather but false -*you can't predict stress* *A Valid Eq Prediction*: -specify a time, a location, size (magnitude), state a formal probability -can be *long term, intermediate term, short term*, and immediate -High probability that happen on major faults in next century -when is the wrong question what is the right question, been focusing on the what will happen with simulations different approaches to predictions fault into *deterministic methods*: -search for precursers; stiff knee starts eq, some prior behavior that occurs before the eq that determines the Eq -probabilistic system; using past behavior to future based on system in the before past by dating fault planes, doing paleoseismology, stuff like that can see big one on SA every 100 yrs and that the slip rate is constant -recurrence interval is 100yrs, 161 yrs since the last one w variations of recurrence intervals, 100 +/- another 100 yrs; the longer we go more likely to have an Eq -*rate of elastic strain communication is not constant*

Special Studies Zones Act (SSZ Act) (1971)

signed into law in California following the 1971 San Fernando earthquake 1. The California State Geologist compiles and published map delineating active faults zones, called *Special Studies Zones* of California. 2. The local governments *regulate constructions within the Special Studies Zones*, and prohibit building construction for human occupancy across an active fault trace. 3. Prospective *buyers* of any real property located within the Special Studies Zones *must be notified* of the fact by the sellers or by their representing brokers.

Cascadian subduction zone

the boundary between the Juan de Fuca and North American plates, is a very long sloping fault that stretches from mid-Vancouver Island to Northern California. -convergent plate boundary

Measuring Plate Motion Rates

• New crust forms and records the magnetic field of the earth • Geochronology can directly date the "stripes" to get rates over millions of years -Harry hess looked at sea floor age in ridges polarized go back older, saw symmetry