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Earthquakes Study Guide

Deformation is the change in the shape of rock in response to stresses placed on it.

Plastic deformation results in folding.

Elastic deformation leads to earthquakes.

An earthquake is the shaking of the Earth’s lithosphere that is caused by the energy released when rock breaks.

Most earthquakes occur along plate boundaries.

Focus: the point along a fault at which the first motion of an earthquake begins

Epicenter: the point on Earth’s surface directly above the earthquake’s starting point, or focus

You need 3seismograph readings to triangulate the location of an epicenter

The simplest method used to find the epicenter of an earthquake is the S-P method (S wave arrival time minus P wave arrival time).

Seismic waves: a wave of energy that travels through the Earth, away from an earthquake in all directions

Body waves

  • P waves, also know as primary waves, or pressure waves
  • Can travel through solids and liquids
  • Are the fastest and first to arrive at a seismograph
  • Cause particles of rock to move in a back and forth motion like an accordion
  • S waves, also known as secondary waves, or shear waves
  • Can only travel through solids
  • Are slower than p waves
  • Cause particles of rock to move in a side to side direction

Surface waves

  • Move along the Earth’s surface
  • Slowest moving seismic waves
  • Cause the most destruction

A seismograph is an instrument that records vibrations in the ground and determines the location and strength of an earthquake

A seismogram is a tracing of earthquake motion that is created by a seismograph

Richter magnitude scale: measures the strength of an earthquake by measuring ground motion recorded on seismographs

Uses Arabic numbers

Each time the magnitude increases by 1 unit the ground motion becomes 10 times larger

Modified Mercalli Intensity Scale: measures the degree to which an earthquake is felt by people and the amount of damage caused

Uses Roman numerals

Intensity can vary from place to place

Earthquake Quiz Study Guide created 7 June 2012 by B. Ferri – edited 12 December 2016