111-pp24 - UNIVERSITY OF SOUTH ALABAMA Last time. Faults...

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1 GY 111: Physical Geology GY 111: Physical Geology UNIVERSITY OF SOUTH ALABAMA Lecture 24: Earthquakes Lecture 24: Earthquakes Last time… A) Types of Brittle Deformation B) Types of faults/terminology C) Faults on maps Faults (Brittle Deformation) Brittle Deformation When rocks break, one of 3 things can occur: 1) cracking/fracturing 2) jointing 3) faulting Brittle Deformation Faults come in two main flavors: Dip Slip: movement is in the direction of the dip of the fault plane. Strike Slip: movement is in the direction of the dip of the fault plane. Fault Terminology All faults share some features. All active faults are subject to earthquakes Faults on Maps There is a special class of reverse fault that is common in mountain belts Thrust Faults
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2 Today’s Agenda Earthquakes A) Seismic waves and the Earth's interior B) Earthquake intensity and magnitude C) Seismographs and locating earthquake epicenters on maps D) Case Studies Web notes 24: GY 111 Lab Manual Chapter 7 Internal “guts” of the Earth The 4 layers of the Earth are distinguished on the basis of geophysics , specifically the way that seismic waves travel through the Earth. Seismic Waves Three major types of seismic waves are distinguished: 1) P-waves ( Primary ) travel by compression 2) S-waves ( Secondary ) travel by shear 3) Surface waves ( Long waves ) travel along the surface Seismic Waves P and S-waves are called body waves because they travel through the Earth. P-waves travel through all media and are the fastest (4+ km/s) S-waves cannot pass through liquids and are slower (3+ km/s) Seismic Waves Surface (Long waves) are also divisible into 2 types according to vibration direction. (don’t worry about this for any tests). Seismic Waves As P and S-waves travel through the Earth, they speed up and slow down according to the density of the materials they pass through. This results in wave refraction. If an earthquake is powerful enough, seismic waves can make it around the world. Propagation of P-waves
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3 Seismic Waves But wave refraction results in the formation of “ shadow zones ” where P or S-waves do not occur. P-wave shadow zones
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This note was uploaded on 02/04/2012 for the course GLY 111 taught by Professor Haywick during the Fall '11 term at S. Alabama.

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111-pp24 - UNIVERSITY OF SOUTH ALABAMA Last time. Faults...

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