Transcript Ch 4 Earthquake slide show

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Earthquakes
Table of Contents
Forces in Earth’s Crust
Earthquakes and Seismic Waves
Monitoring Earthquakes
Forces in Earth’s Crust
Stress in Earth’s Crust
Stress can push, pull, or squeeze rock in
Earth’s crust. Three kinds of stress can occur
in the crust.
Forces in Earth’s Crust
Faults
The three main types of faults are
defined by the direction in which rock
moves along the fault.
Forces in Earth’s Crust
The low angle of a thrust fault allows rock in the hanging wall to be
pushed great distances. For example, over millions of years, rock along
the Lewis thrust fault in Glacier National Park has moved 80 kilometers.
Forces in Earth’s Crust
Anticlines and Synclines
Compression can cause folds in the crust. Two types of folding are
anticlines, which arch up, and synclines, which dip down.
Forces in Earth’s Crust
Tension and Normal Faults
As tension forces pull the crust apart, two normal faults can form a faultblock mountain range.
Forces in Earth’s Crust
The Kaibab Plateau
Look at the sequence of drawings. In your own words, describe what
happens in the last two diagrams.
Earthquakes and Seismic Waves
Earthquakes start below the
surface of the Earth. An
earthquake's seismic waves
carry energy up toward the
surface and down through the
interior.
Earthquakes and Seismic Waves
Seismic Waves
The diagram shows how seismic waves traveled during
an earthquake along the Denali fault.
Earthquakes and Seismic Waves
P, S, and Surface Waves
Earthquakes release stored energy
as seismic waves.
Earthquakes and Seismic Waves
Modified Mercalli Scale
The Modified Mercalli scale uses Roman numerals to rate the damage
and shaking at any given location, usually close to the earthquake.
Earthquakes and Seismic Waves
Earthquake Magnitude
The table gives the moment magnitudes of some recent earthquakes.
Earthquakes and Seismic Waves
Seismic Wave Speeds
Seismographs at five observation stations recorded the arrival times of
the P and S waves produced by an earthquake. These data were used
to draw the graph.
Earthquakes and Seismic Waves
An Earthquake’s Epicenter
The map shows how to find the epicenter of an earthquake using data from
three seismographic stations.
Monitoring Earthquakes
Seismic Data From the USArray Project
In 2004, scientists in the USArray project placed 400 seismographs across
the western United States. Every month, 18 seismographs are picked up
and moved east, “leapfrogging” the other seismographs.
Monitoring Earthquakes
Recording Seismic Waves
In a simple seismograph, a pen attached to a suspended weight records
an earthquake’s seismic waves.
Monitoring Earthquakes
Seismograms
When an earthquake’s seismic waves reach a simple seismograph, the
seismograph’s drum vibrates. The vibrations are recorded by the
seismograph’s pen, producing a seismogram.
Monitoring Earthquakes
Earthquake Risk
The map shows
areas where serious
earthquakes are likely to
occur, based on the
location of past
earthquakes across the
United States.
Monitoring Earthquakes
Earthquakes Around the World
Earthquakes are closely linked to plate tectonics.
The map shows where past earthquakes have
occurred in relation to plate boundaries.