Lesson 1: What Is an Earthquake? Earth Science A Unit 7: Earthquakes and Earth's Interior

What is a fault?

A fault is a fracture in Earth where movement has occurred.

What are foreshocks and aftershocks?

Aftershocks are smaller, weaker earthquakes that occur after the main earthquake. Foreshocks are small earthquakes that come before a major earthquake.

What is an earthquake?

An earthquake is the motion that results as rocks release elastic energy.

What are two ways in which deformation affects rock?

Deformation affects rock by causing it to bend. At the same time, elastic energy is stored in the rock.

Describe the cause of earthquakes.

Earthquakes are caused by the release of elastic energy stored in rock that has been subjected to great forces. This causes the vibrations of an earthquake as the rocks elastically return to their original state.

What is meant by elastic rebound?

Elastic rebound is the process by which deformed rocks first bend and then break, releasing energy.

Why do most earthquakes cause little damage and loss of life?

Most earthquakes do little damage because most of them occur in areas that are not populated.

How are an earthquake's fault, focus, and epicenter related?

The focus of an earthquake is the place within Earth where the earthquake begins. The spot on the surface directly above the focus is the epicenter. Most earthquakes are usually associated with large fractures in the crust known as faults.

earthquakes are usually associated with

faults

When an earthquake occurs, energy radiates in all directions from its source. The source is also referred to as the

focus

What fault was involved in the 1906 San Francisco earthquake?

the San Andreas fault

An earthquakes epicenter is

the place on earths surface directly above the focus

What is elastic rebound?

the tendency for the deformed rock along a fault to spring back after an earthquake occurs