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.