earthquake

Introduction

CE5

Worldwide pattern of earthquake activity: The dots indicate the epicenters of all earthquakes recorded during a recent 10-year period.

CE5

earthquake, trembling or shaking movement of the earth's surface. Most earthquakes are minor tremors. Larger earthquakes usually begin with slight tremors but rapidly take the form of one or more violent shocks, and end in vibrations of gradually diminishing force called aftershocks. The subterranean point of origin of an earthquake is called its focus; the point on the surface directly above the focus is the epicenter. The magnitude and intensity of an earthquake is determined by the use of scales, e.g., the moment magnitude scale, Richter scale, and the modified Mercalli scale.

Sections in this article:

Introduction
Major Earthquakes
Earthquake Warning Systems
Damage Caused by Earthquakes
Seismic Waves
Causes of Earthquakes
Bibliography

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