Chapter 19- Earthquakes

What are 2 things that seismologists looks at when forecasting earthquakes?

-the history of earthquakes in the area -the rate at which strain builds up on the rocks

How many seismic station are needed to find epicenter?

3 are needed. When the 3 circles intersect, that is where your epicenter is located

What is a travel-time curve?

A graph that helps people figure out the distance to the epicenter of an earthquake

Seismic Gaps

An area along a fault line that hasn't had an earthquake in a long time

Secondary Waves

Called S- waves travel slower than p-waves causes rocks to move at right angles move through solids only

Primary Waves

Called p-waves squeeze and push rocks the direction the wave is traveling move through liquids and solids

What are the 3 types of stress?

Compression Tension Shear

Soil. Liquefaction

In areas that have sandy, wet soil it causes the ground to behave like a liquid and buildings will sink into the ground

What is tension?

Material is lengthened

What is shear?

Material is twisted

What is the most famous strike-slip fault?

San Andreas in CA

What kind of earthquake is the most damaging?

Shallow focus

Strain

The deformation of materials is response to stress

What is compression?

Volume of material is decreased

How do you find the distance to the epicenter?

You need to find the difference in arrival times for the P and S waved and then match up to the travel time curve

Fault

a fracture or crack in the crust where the earth moves

Seismometer

a sensitive instrument that detects seismic waves

Reverse Fault

form as a result of compression stress on the rock. It will form at a convergent boundary.

Strike-slip Fault

forms as a result of shear stress. It will form near a transform boundary.

Normal Fault

forms as a result of tension stress on the rock. It will form near a divergent boundary.

Elastic deformation

happens under low stress. A material is bent, stretched, or compressed. When the stress is removed from the material, then it will return to its normal conditions.

Tsunami

large ocean wave generated by an earthquake on the ocean floor

Richter Scale

measures energy released by an earthquake called magnitude

Moment Magnitude Scale

measures energy released by quake and -size of fault rupture -amount of movement along fault - what type of rocks moved

Modified Mercalli Scale

measures the intensity or damage done by an earthquake

Why was the Haiti earthquake so bad?

shallow focus poor infrastructure(building standards) poor communication high population density

Surface waves

slowest type of wave cause the most damage to buildings

Plastic Deformation

strain will produce permanent deformation to the object. It is stretched beyond its elastic limit and has failed.

Epicenter

the point on earth's surface directly above the focus

focus

the point underground where the waves originate

Seismogram

the recording produced from the seismometer that shows the seismic waves

Stress

the total force acting on crustal rock per unit of area

Seismic Waves

vibrations of the ground during an earthquake

Pancaking

when buildings collapse from the top floor down on top of the lower floors. Looks like a stack of pancakes.