Earthquakes Chapter 6

Seismogram

the record made by a seismograph

strike-slip fault

the rocks on either side of the fault slip past each other sideways, with little up or down motion

fault

A break in the earth's crust

Richter scale

A scale that rates an earthquake's magnitude based on the size of its seismic waves.

Mercalli scale

A scale that rates earthquakes according to their intensity and how much damage they cause at a particular place

convergent boundary

A tectonic plate boundary where two plates collide, come together, or crash into each other.

S waves (secondary waves)

Are produced when material moves either vertically or horizontally and travel only within the uppermost layers of Earth.

Seismograph

Instrument used to measure horizontal or vertical motion during an earthquake.

magnitude

Measure of the energy released during an earthquake

Epicenter

Point on Earth's surface directly above an earthquake's focus

tension

Stress that stretches rock so that it becomes thinner in the middle

Intensity

The amount of energy per second carried through a unit area by a wave.

divergent boundary

The boundary between two tectonic plates that are moving away from each other

Compression

The part of a longitudinal wave where the particles of the medium are close together.

focus

The point beneath Earth's surface where rock breaks under stress and causes an earthquake

reverse fault

a fault in which the hanging wall moves up relative to the footwall

P waves

a seismic wave that causes particles of rock to move in a back-and-forth direction

surface waves

a type of seismic wave that forms when P waves and S waves reach Earth's surface

dip-slip fault

blocks move parallel to the dip of the fault

normal fault

break in rock caused by tension forces, where rock above the fault surface moves down relative to the rock below the fault surface

Seismoscope

important scientific instrument used to detect earthquakes