Earth and Space Science CH 12 Pretest

seismic gap

a fault area where few quakes have
occurred recently, but where strong
quakes have occurred in the past

Richter scale

a scale that measures the ground motion from earthquakes

body wave

a wave that travels through the body of a medium

tsunami

A giant wave usually caused by an earthquake beneath the ocean floor.

modified Mercalli scale

Scale expressing intensity

surface wave

a wave that travels along the surface of a body, not through the middle

seismograph

an instrument used for detecting an recording vibrations in the ground.

foreshock

A little earthquake that might preceed a larger one.

elastic rebound

the sudden return of elastically deformed rock to its undeformed state

moment magnitude

A measurement of earthquake strength based on the size of the area of the fault that moves

What can happen to tall buildings during an earthquake?

They can sway and even tip over

If you are inside during an earthquake?

stand in a doorway or crouch under a desk

Why do seismic waves speed up at about 30 km beneath the surface?

because Earth's mantle is denser than the crust

Why do earthquakes usually occur at plate boundaries?

because the street on the rocks of the plates is greatest at the boundaries.

If you are in a car during an earthquake, you should

stop away from structures that might collapse

When an earthquake occurs

stay calm

How do scientist find the distance to an epicenter?

by analyzing arrival times of P waves and S waves

Scientists monitor natural gas seepage from rocks because

it may mean trouble

Where does the first motion of an earthquake occur?

at the focus

What is another name for a P wave?

a primary wave