Earthquakes: The Basics

An earthquake is what happens when two blocks of the earth suddenly (a)   past one another.

Which of the of the following shows the correct order?

• foreshock, mainshock, aftershock

• mainshock, aftershock,

  foreshock

• mainshock, foreshock, aftershock

• aftershock, mainshock, foreshock

Since the edges of tectonic plates are rough, they get stuck while the rest of the plate keeps moving. Finally, when the plate has moved far enough, the edges unstick on one of the faults and there is an ____.

• tsunami

• volcanic eruption

• thunder clap

• earthquake

Most earthquakes happen far from tectonic plate boundaries. True or False?

• True

• False

When the force of the moving blocks finally overcomes the friction of the jagged edges of the fault and it unsticks, all that stored up energy is released. The energy radiates outward from the fault in all directions in the form of seismic waves like ripples on a pond. The seismic waves ____ the earth as they move through it, and when the waves reach the earth’s surface, they _____ the ground and anything on it, like our houses and us!

(a)  

Earthquakes are ___ by instruments called seismographs.

• caused

• recorded

• stopped

The size of earthquakes is measured by its ______.

• length

• width

• damage

• magnitude

Which of the following is true of P waves?

• arrive before S waves and are faster than S waves

• arrive after S waves and are slower than S waves

Scientists use a method called triangulation to find the location of an earthquake. How many seismograph recordings are necessary for this method?

• 1

• 2

• 3

• 4

Scientists can accurately predict exactly when an earthquake will happen.

• True

• False