Geo008 Midterm 1

Body Waves

seismic waves that travel through the Earth's interior

Transform

slide past eachother. Horizontal shearing, parallel to eachother, nothing happens. Strike-slip <-- -->

inner core

solid due to high pressure. Pressure increases with increasing depth.

spreading rate for mid oceanic ridge

spreading rate =steps/Min

Fault

surface or narrow zone with shear displacement along the zone. will always be acute (180 degrees)

Wave attenuation + Geometrical spreading =

the farther from the site of an earthquake is less intense shaking and deeper depths = less intensity Local geological conditions such as materials like fill and mud determine intensity (the Bay Area fill amplified shaking).

what happens when you get lower?

the more dense material gets

what is the epicenter?

the point on Earth's surface directly above the focus

conveyor belt theory

the volcanoes create new crust and the lithosphere expands on both directions.

Asperity on fault

there are bumps, when it slips across the bump, it creates earthquakes.

seafloor bathymetry

topography of the sea floor; highly variable; three kinds of landscape

San Andreas fault

transform plate boundary/strike-slip, right lateral

outer core

very dense liquid. flows. Acts as a dynamic for Earths magnetic field. Made up of Iron and Metal.

What is the lithosphere made of?

very hard rock. When pressure is applied it breaks. The lithosphere averages about 100 km thick. crust, above asthenosphere.

earthquakes

violent shaking or shifting motion of the ground caused by the sudden movement of rock far beneath Earth's surface

quick degression

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Japanese Belief

Catfish "Namazu" caused the earth to shake when the gods werent looking.

P.N.C. Egen 1828

Created more detailed scale

seismometer used to measure:

Displacement, Velocity, and acceleration. Many are needed in order to gather this information.

Russian Beliefs

Dog "Kozei" shook snow off his coat and the earth trembled.

Mongolian Belief

Earth on the back of a frog

Chinese Beliefs

Earth on the back of giant ox

Why are earthquakes and volcanoes in the same areas?

Volcanoes are created by plate boundaries that also create earthquakes.

Surface Waves

seismic waves that travel along the Earth's surface

Geometrical Spreading

the farther the wave travels, the more energy is lost by absorption

seismic waves

vibrations that travel through Earth carrying the energy released during an earthquake

Greeks Believed

Poseidon caused earthquakes with his temper tantrums

convection

Process by which, in a fluid being heated, the warmer part of the mass will rise and the cooler portions will sink.

Love Wave

Surface waves that shear the ground in a horizontal direction. Can only travel through solids. Perpendicular to propagation. Third to arrive.

Rayleigh Wave

Surface waves that travel in a backward-rotating, retrograde/elliptical motion, causing both vertical and horizontal ground movement. Can travel through solid, liquid, and gas. Fourth to arrive. Dangerous.Counter-clockwise movement.

fault plane

The flat surface of the fault where the earth movement occurs in an earthquake

continental drift

The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations

kilogram

Unit used for mass

California fault

What are the two transform fault boundaries?

Seismic wave velocity

When seismic waves travel through the interior, they reflect, refract, and bounce off surfaces.

Siesmogram

an instrument that measures the damage of the earthquake

strain

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three components to ground motion

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Modified Mercalli Scale

12 levels of intensity in (Roman Numerals) is used in the USA and Western Europe as of now

Established Elastic Rebound Theory

1906 San. Fran. earthquake

Indian Belief 1

7 serpents guarded the earth, earth shook when they took turns holding it.

Oblique fault

A combo of vertical (dip) slip and horizontal (strike) slip; hanging wall slips diagonally

what is the crust?

A layer of solid rock that includes dry land and the ocean floor. Main elements are Oxygen and Silicon., thin outermost layer of the earth

right-lateral

A strike-slip fault in which the block seen across the fault appears displaced to the right.

Convergent Plate Boundaries

A tectonic plate boundary where two plates collide, come together, or crash into each other. Shorten & compress. subduction zone. Reverse/Thrust Fault.Compressional-> | <-

Strike-slip

A type of fault where rocks on either side move past each other sideways with little up or down motion (shear stress)

Normal fault

A type of fault where the hanging wall slides downward; caused by tension in the crust. Tension lengthens an object.

left-lateral

As you face the fault, the opposite side of the fault moves to the left.

Divergent Plate Boundaries

Boundary between tectonic plates in which the two plates move away from each other, and new crust is created between them. Extensional. Normal Fault-hanging walls go down. Mid-Oceanic ridge. Tensional<- | ->

continental seismic network

Created a dense network of seismometers within the continent.

crest

Highest point of a wave

wavelength

Horizontal distance between the crests or between the troughs of two adjacent waves

who first tried to explain why earthquakes occurred?

Gelasius

Asthenosphere

Soft layer of mantle under the lithosphere that is hotter and under more pressure, is warmer than the lithosphere which causes it to be less rigid and can bend like plastic. Flows with pressure.

Mesosphere

Stiff plastic

Chickasaw Indians

God stepped on reelfoot and caused earthquakes

seafloor spreading

Hess's theory that new ocean crust is formed at mid-ocean ridges and destroyed at deep-sea trenches; occurs in a continuous cycle of magma intrusion and spreading

1891 Mino-Owari earthquake

Identifiable cause by B. Koto formation of fault scarp

heterogeneous slip

Indonesian 2004 subduction zone slipped causing a 9.2 earthquake. Began South and propagated North. 1300 km fault. lasted 10 min. The entire fault did not slip uniformly due to asperity.

Scandinavians Belief

Loki caused earthquakes when he tried to dodge snake poison dropping onto his face as his sister empty the bowl that caught the poison.

Major Plate Boundaries

Pacific Plate, North American Plate, Nazca Plate, South American Plate, Australian Plate, Antarctic Plate, African Plate, Eurasian Plate

strike-slip motion

Plates move in a jerky motion, when they move an earthquake is created, stress is accumulated and then released by slipping.

S-wave

Secondary waves, shearing waves (vertical or horizontal) move up/down, doesn't move through liquid. Second to arrive. Perpendicular to propagation.

subduction zone

The region where oceanic plates sink down into the asthenosphere.

Earthquake studied by john mitchell in 1755.

The Libson Earthquake

footwall

The block of rock that forms the lower half of the fault. below plane

hanging wall

The block of rock that forms the upper half of a fault. above plane

what is the earths focus?

The crust, the outer core, the mantle, and the inner core

seismic array

The deployment over a large area of a large number of seismographs with which to probe the earth's interior.

intensity

ground shaking determined by the manner and amount of energy released at the source , distance from the source (including depth of the source), and the material and topography at the site experiencing movement.

newtons

The unit of measurement for force

what is the mantle?

hot layer between the crust and core

land that sits on mid-oceanic ridge

iceland

period

length of time for one full cycle.

acceleration

m/s^2

What does earths core do?

makes the heated material go up which drives the plates along with gravity. the heat that goes up is heated magma that drives the plate tectonics to move.

force=

mass * acceleration

frequency

number of complete oscillations measured in hertz.

Epicenter

point on surface directly above focus

P-wave

seismic body (underground) primary wave that travels at about 6km/s through Earth's crust, causing the ground to move in the direction of the wave's motion, A type of seismic wave that compresses and expands the ground. First to arrive. Parallel to propagation.

reverse polarity

When the earth's magnetic field points south instead of north. the poles switch/reverse over geologic time. The reverse is instant and not gradual.

Greeks (Anaxagoras) believed

a collision of gases in caves created ground shaking and caused earthquake. Aristotle believed gases caused earthquakes.

Wave Attenuation

a portion of a wave energy that is absorbed by the material through which it passes. This results in the decrease of amplitude and therefore ground shaking intensity.

Why do plates move?

because plumes (molten rock) under volcanoes that want to come up stays in the same place over geologic time. so based on the plume we can find out how fast plate tectonics are moving. the closest volcano to the plume is the youngest volcano.

earthquakes are measured in waves

by measuring the amount of earthquake damage or shaking that is felt is rated using the Modified Mercalli scale. They ripple like water.

Reverse

compressional, hanging wall moves upward

What did John Mitchell do?

connected the relationship between earthquakes and faults. Believed that underground waves caused earthquakes.

Plate Tectonics

constantly moving in limited space, this causes friction, it moves a few centimeters each year.

Joham Noggerath 1847

created a map for the Rhenish earthquake to trace areas with similar intensities.

Domenico Pignataro 1783

created first scale to determine the strength of an earthquake

regional seismic network

dense regional network. California is the most dense.

Azimuth (direction)

direction determines intensity as well. A site close to the direction of rupture along a fault will be greater in intensity.

half-spreading rate for mid-oceanic ridge

divide spreading rate by 2

cross section

earth cut open and viewed from the side

Earths Magnetic Field

every few million years the magnetic field swaps so north and south will switch. magnetic reversals. rocks also show the reverse in the magnetic field. rocks are polarized in a normal position right now the last time it reversed was around 1 million years ago. new rock is created and is oriented the way earths magnetic field is then it is moved from the center

hypocenter

focus point of an earthquake

friction

force that resists relative movement.

Stress

force/area

Indian Belief 2

four elephants held up earth, stood on top of turtle, which stood on a cobra.

Aztec Belief

gods and volcanoes caused earthquakes