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Introduction to Seismology
Geology 5640/6640 Introduction to Seismology 11 Jan 2017 Last time: Course overview Discussed: syllabus, resources, course objectives The observation: A seismogram is a record of ground motion (specifically, ground acceleration!) as a function of time *Tried* to view animations of vertical movement in EarthScope’s Transportable Array seismic network (for the Feb 2008 Wells, NV and several Gulf of California earthquakes) Read for Fri 13 Jan: S&W 1-28 © A.R. Lowry 2017
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Trabant et al. (2012) Seismol. Res. Lett.
Trabant et al. (2012) Seismol. Res. Lett. Various Gulf of California earthquakes,
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What’s the point of showing this?
Seismology provides crucial information about the nature of high energy seismic sources like earthquakes!
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M7.2 El Mayor- Cucapah Event (2010)… Finite fault model
( GEER_Post%20EQ%20Reports/ Baja%20California_2010/ Baja10_Ch02.html)
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Note however that earthquakes aren’t the only significant
seismic energy source on the block!
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A more familiar application of
seismology, for most of you… Would be the application to imaging of the Earth’s subsurface
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For example, seismic reflection* imaging as it is employed in exploration for petroleum and natural gas…
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Seismic Reflections* *Sound waves reflect off of points in the subsurface where rock elastic properties change ( change in rock type, porosity, fluid, etc.). Energy returns are “migrated” to the approximate spatial location of the reflection source to form an image of the subsurface.
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Example of subsurface imaging: thickness of the crust & seismic velocity ratios using P-to-S converted waves from distant earthquakes
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Example of subsurface imaging: Upper mantle VP, VS and VP/VS
velocity ratios from waves from distant earthquakes (Schmandt & Humphreys, EPSL, 2010)
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