Earthquakes Flashcards
Earthquake?
Vibrations in the ground that result from movement along faults, or breaks in Earths lithosphere.
What are the three types of faults?
Normal, Reverse, and Strike-Slip.
What is a normal fault?
Forms when forces pull rocks apart along a divergent plate; blocks of rock above fault moves down.
What is a Strike-slip fault?
Two blocks of rock slide horizontally past each other in opposite directions.
What is a reverse fault?
Forces pushes two blocks of rock together with the rock above the fault moving up.
Focus?
Point beneath Earths surface where rock under stress breaks to cause an earthquake.
Epicenter
Point on earths surface directly above the focus.
Seismic waves
Waves that carry energy of an earthquake away from the focus; there are three types..
What are the three types of waves?
Primary waves, Secondary Waves, and Surface waves.
What is a Primary wave?
Compression waves that travel through solids and liquids, compressing and expanding the material they pass through temporarily changing volume.
What is a secondary wave?
Only travel through solids and temporarily change the shape, but not the volume of the material they pass through; move slower than P waves.
What is a surface wave?
Move slower than P&S waves, but can produce severe ground movement with a wave like motion.
How do you locate an earthquakes epicenter?
Is done using triangulating data from at least three different seismometers or devices that measure and record ground motion and helps determine the distance seismic waves travel.
What are the steps to locating an earthquakes epicenter?
- Find the arrival time difference between the first P wave and S wave which is called lag time.
- Find the distance to the epicenter by using a graph of lag time vs distance, then go from y axis to line and read down to x axis
- Locate the epicenter by using a map scale to mark radius on a compass then draw a circle around each seismometer location to find intersecting point.
