Lab6 - Name: SID: Lab 6: Earthquakes and Seismic Risk...

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Name: SID: Lab 6: Earthquakes and Seismic Risk Introduction: Earthquakes are a natural phenomenon in which ground shaking is caused by the sudden release of strain energy stored in elastic rocks, analogous to the snapping and shuddering of a twig when it is bent beyond its failure point. In the case of an earthquake, the stored elastic strain energy is released through slip across a crack or fault, and a portion is radiated as seismic waves. Seismic waves are of immense importance in the study of the earth; not only do they tell us about the nature of the earthquake process itself, but they also provide a direct sampling of the deep interior of the earth. Much of what we know about the structure of the earth is due to the study of seismic waves. There are also more practical reasons for the study of seismic waves: a better understanding of the generation of damaging strong ground motions from earthquakes will reduce future earthquake loses. Objective: In this lab, you will learn to pick P and S waves from seismograms, locate an earthquake, calculate the local (Richter) magnitude, and perform a basic seismological hazard analysis. -------------------------------------------------------------------------------------------------------------- Bay Area Fault Systems
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Earthquake Location and Magnitude Location is the first information that a seismologist seeks after an earthquake. The location is fundamental and is needed for most other types of analyses that follow. For example, the location is an essential ingredient in the estimation of magnitude, focal mechanism, and ultimately damage levels. The location of earthquakes is also of critical importance when the waveform or traveltime data is to be used to probe the interior of Earth. A number of different methodologies may be used to locate earthquakes. The basic idea is simple triangulation, however, and the information that is needed is the arrival time of the direct P-wave and S- wave measured in some absolute time base. Historically, seismographs have made use of accurate clocks for just this purpose. Today, GPS clocks have accuracy to 5 ms (microseconds), and we typically use many observations of wave arrival time. Observations are then digested by computers that solve problems using linear algebra.
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This note was uploaded on 09/17/2009 for the course EPS 50 taught by Professor Staff during the Spring '08 term at Berkeley.

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Lab6 - Name: SID: Lab 6: Earthquakes and Seismic Risk...

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