GEOL 2301 Lesson 3 Chapt 11

Primary/P-Waves

"push/pull" waves, they momentarily push (compress) & pull (stretch) rocks in the direction the wave is traveling.

Elastic deformation

An example of the elastic rebound associated with earthquakes.

Tohoku, Japan (2011)

As of 2012, which of the following earthquakes has been observed to have the greatest fault slips?

Saturated

Because rocks cannot store enough energy to register a 9, the rocks will berak and release before hitting 9 on the Richter Scale, which is why it is considered __.

Seismic Gap

Believed to be zones that are storing strain that will be released durig a future eathquake - Quiet zones

Modified Mercalli Intensity Scale

Developed in 1902 - a more reliable intensity scale which in a modified form is still used today - Devlop using California buildings as its standard.

Reverse Faults

Faults including low-angle thrust faults, associated w/convergent plate boundaries. Generated by compressional forces along subduction zones & where continental collisions result in mountain building.

Strike-Slip Faults

Faults that are the result of shear stresses & exhibit mainly horizontal slip that result in large segments of Earth's crust to grind past each other.

Normal Faults

Faults that occur where tensional stress causes Earth's crust to be stretched & elongated.

Earthquake

Ground shaking caused by the sudden & rapid movement of one block of rock slipping past another along fractures in Earth's crust called faults.

Seismic Waves

In the open sea, they havea wave length of many miles & wave height of a few feet.

Time interval between the P and S waves

Information needed when determining the distance from the focus of an earthquake to the seismic receiving station.

Transform Faults

Large strike=slip faults, like the San Andreas Fault, are called __ when they form plate boundaries

Amplify

Liquefaction will ___ the power of seismic waves.

Tsunami

Major undersea earthquakes occasionally set in motion a series of large ocean waves that are known by the Japanese "harbor wave".

Intensity

Measure of the amount of ground shaking at a particular location, based on observed property damage.

Richter Scale

Measures the actual amount of energy releases, by measuring the waves themselves, the amplitude of the waves - not relying on building damage.

Moment Magnitude Scale

Measures the total energy released during an earthquake by determining the average amount of slip on the fault, the area of the fault surface that slipped,a dn the strength of the faulted rock.

preexisting faults

Most large earthquakes occur along __ where past earthquakes have caused the crustal rocks to rupture or break into two or more units.

Lifts a large slab of seafloor

Most tsunamis are generated by displacemen talong a megathrust fault that suddenly __.

Divergent Plate Boundaries

Normal Faults associated __ , mainly seafloor spreading centers & continential rifts.

Human vocal cords

P-Waves are compared to ___ as they move air back & forth to create sound.

Megathrust Fault

Plate boundary between a subducting slab of oceanic lithosphere & the overlying plate - Large thrust/reverse faults.

H.F. Reid

Researcher that developed elastic rebound after the 1906 San Francisco earthquake.

Fault Creep

Slow, gradual displacement along a fault w/out the accumulation of significant strain.

Aftershocks

Smaller earthquakes of lesser magnitude that follow a major earthquake.

Seismic

Stored-up energy released by earthquakes.

Subduction Zones

The deepest (deep focus) earthquakes are associated with?

Finding the Epicenter of Earthquake

The difference inthe velocities of P and S waves provides a method for locating __. Since P-waves travel faster than S-waves, the further the epicenter is from the recording instrument, the reater the difference in the arrival times of the first P-wave compared to the first S-waves.

Focus (Hypocenter)

The exact location on the fault where slippage occurs/begins.

Epicenter

The location on the Earth's surface directly above the point of slippage/hypocenter.

Liquefaction

The phenomenon of transforming a somewhat stable soild into mobile material capable of rising towards Earth's surface - ground may not be able to support buildings, underground storage tank, sewer lines - may float towards surface.

seiches

The rhythmic closhing of water in lakes, resevoirs/dams, adn enclosed basins such as the Guld of Mexico.

Surface waves

The seismic wave that will have the greatest amplitude on a seismogram.

Rope

The wave is illustrated by fastening one end of a ___ and shaking the other end.

P-Waves

This type of wave can move through the outer liquid core , solids, liquids, & gases -they are the fastest

S-Waves

This type of wave can not move through the outer luid core, liquids or gases.

Surface Waves

This type of wave caused most of the earth's damage. The latter motion damages the foundations of structures.

San Francisco

Town destroyed by an earthquake that cause mass fire by breaking gas, electric, & water lines.

Seismic gap

Unusually quiet zones along typially active faults.

Secondary/S-Waves

Waves that "shake" the aprticles at right ngles to their direction of travel.

10x

When going from a 5 to a 6 on the Richter Scale, what is the increase in amplitude of seismic waves.

New Madrid, Missouri

Where some of the strongest/worse earthquakes recorded on the North America continent (three recorded).

China

Where was the earliest seismograph developed?

P-waves

Which seismic wave will be released first during an earthquake?

Convergent

Which tectonic boundary is associated with megathrust faults?

Soft seiments

____ or unconsolidated material will amplify the vibrations allowing materials to shake more.

Seismometers

instruments that sense earthquake waves and transmit them to a recording device.

Fault Slip

measurement of displacement on the fault surface.

Seismograms

records of seismic waves.