# 8.2 Measuring Earthquakes

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8.2 Measuring Earthquakes
Prentice Hall 2006 Earth Science

Identify the three types of seismic waves
Objectives Identify the three types of seismic waves Explain how to locate the epicenter of an earthquake Describe the different ways earthquakes are measured.

Vocabulary Seismograph Seismogram Surface wave P wave S wave Moment magnitude

8.2 Objective 1 Identify the three types of seismic waves

Identify the three types of seismic waves
The study of earthquake waves is called _________. The recording instrument is called a _______________. The record from a seismograph is called a _______________. A seismogram records the ______________ of the Earth. Tarbuck 6.6 Tarbuck 6.7

Identify the three types of seismic waves
have a __________ motion and have the _________ velocity of all waves. Tarbuck 6.8

Identify the three types of seismic waves
Surface waves have a complex motion and have the slowest velocity of all waves. Body waves Primary waves. also called _____ waves P waves exhibit a _______________ (compression-rarefaction) motion. Primary waves travel through ________________________________. P waves have the ______________of all seismic waves. Identify the three types of seismic waves

Identify the three types of seismic waves
Surface waves have a complex motion and have the slowest velocity of all waves. Body waves Primary waves. also called P waves P waves exhibit a push-pull (compressional) motion. Primary waves travel through solids, liquids, and gases. P waves have the greatest velocity of all seismic waves. Secondary (S) waves create a ___________ motion. only travel through ___________. velocity is ____________________________________. Identify the three types of seismic waves

8.2 Objective 2 Explain how to locate the epicenter of an earthquake

Locating an Earthquake
The focus is the place within Earth where Earthquake waves originate. Epicenter is the point on the surface directly above the focus. The epicenter is located using the ______________________________________________________, which can be related to distance.

Locating an Earthquake
The focus is the place within Earth where Earthquake waves originate. Epicenter is the point on the surface directly above the focus. The epicenter is located using the difference in arrival times between P & S wave recordings, which can be related to distance. ______________are needed to locate an epicenter. A circle equal to the epicenter distance is drawn around each station. The ___________ of the three circles is the epicenter.

Earthquake distribution
Earthquake zones are closely associated with plate boundaries particularly ______________________________________________________________________________________________ Shows distribution of earthquakes w/ > 5.0 magnitude between 1980 & 1990.

8.2 Objective 3 Describe the different ways earthquakes are measured.

Earthquake intensity & magnitude
Three scales Modified Mercalli Richter Moment Magnitude

Earthquake intensity & magnitude
Tarbuck Table 1 _____________________ is a measure of the degree of earthquake shaking at a given locale based on the amount of damage. Intensity is most often measured by the ________________________________________

Earthquake intensity & magnitude
is a concept introduced by Charles Richter in 1935. measured by the Richter scale ML based on the ____________________________________________________________ Each unit of the Richter magnitude equates to roughly a ____ fold energy increase. ____________________estimate adequately the size of very large earthquakes. Earthquake intensity & magnitude

Earthquake intensity & magnitude
Moment Magnitude scale a ___________________magnitude measurement measures very large earthquakes. derived from the _______________________that occurs along a fault zone, the ___________ of the rupture surface, and _______________strength of the faulted rock Largest earthquakes