# Vocab for Science

## 24 terms

### Stress

pressure or tension exerted on a material object

### Fault

a break in Earth's crust where slabs of crust slip past each other.

### Compression

pushing closer together

stretching

### Shear

sliding in opposite directions

### Earthquake

shaking and trembling that results from the movement of rock beneath Earth's surface.

### Focus

the point beneath Earth's surface where the stressed rock breaks causing an earthquake

### Epicenter

the point on the surface above the focus

### Elastic rebound theory

explains how the rock in the crust behaves

### Seismic waves

the waves produced by earthquakes

### Primary waves

longitudinal seismic waves

### Secondary waves

transverse seismic waves

### Surface waves

When primary waves and secondary waves reach Earth's surface, some of them are transformed

### Triangulation

a trigonometric method of determining the position of a fixed point from the angles to it from two fixed points a known distance apart

### Seismograph

will record the resulting ground movements caused by the seismic waves

### Magnitude

a measurement of its strength based on seismic waves and movement along faults

### Mercalli scale

uses the damage reported by observers to determine how intense the earthquake waves were at that spot

### Richter scale

rates earthquakes according to the size of seismic waves as measured by a seismograph, is a more common method for describing earthquakes

### Moment Magnitude scale

rates the total amount of energy released

### Seismologist

Scientists who study earthquakes

### Aftershock

a smaller earthquake that occurs after a larger earthquake in the same area

### Liquefaction

occurs when an earthquake's violent shaking turns loose, soft soil into liquid mud.

### Tsunami

An earthquake on the ocean floor causes the floor to rise slightly and push water out of its way

### Earthquake risk

locating where faults are active and where past earthquakes have occurred