Smith, Deborah Elaine and Aagaard, Brad T. and Heaton, Thomas H. (2005) Teleseismic Body Waves from Dynamically Rupturing Shallow Thrust Faults: Are They Opaque for Surface-Reflected Phases? Bulletin of the Seismological Society of America, 95 (3). pp. 800-817. ISSN 0037-1106 http://resolver.caltech.edu/CaltechAUTHORS:20121120-093103363
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We investigate whether a shallow-dipping thrust fault is prone to wave-slip interactions via surface-reflected waves affecting the dynamic slip. If so, can these interactions create faults that are opaque to radiated energy? Furthermore, in this case of a shallow-dipping thrust fault, can incorrectly assuming a transparent fault while using dislocation theory lead to underestimates of seismic moment? Slip time histories are generated in three-dimensional dynamic rupture simulations while allowing for varying degrees of wave-slip interaction controlled by fault-friction models. Based on the slip time histories, P and SH seismograms are calculated for stations at teleseismic distances. The overburdening pressure caused by gravity eliminates mode I opening except at the tip of the fault near the surface; hence, mode I opening has no effect on the teleseismic signal. Normalizing by a Haskell-like traditional kinematic rupture, we find teleseismic peak-to-peak displacement amplitudes are approximately 1.0 for both P and SH waves, except for the unrealistic case of zero sliding friction. Zero sliding friction has peak-to-peak amplitudes of 1.6 for P and 2.0 for SH waves; the fault slip oscillates about its equilibrium value, resulting in a large nonzero (0.08 Hz) spectral peak not seen in other ruptures. These results indicate wave-slip interactions associated with surface-reflected phases in real earthquakes should have little to no effect on teleseismic motions. Thus, Haskell-like kinematic dislocation theory (transparent fault conditions) can be safely used to simulate teleseismic waveforms in the Earth.
|Additional Information:||© 2005 Seismological Society of America. Manuscript received 15 August 2003. This material is based on work supported by National Science Foundation Grant 0208494. We thank Chen Ji for modifying his code so we could forward-model teleseismic ground motions for any given slip history. We also thank James Brune, Pascal Favreau, Ruth Harris, Art McGarr, and David Oglesby for their insightful and helpful reviews and Barbara Smith for her editing. Access to the Hewlett-Packard V-Class computer, located at the California Institute of Technology, was provided by the Center for Advance Computing Research.|
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|Deposited By:||Tony Diaz|
|Deposited On:||20 Nov 2012 18:23|
|Last Modified:||20 Nov 2012 18:23|
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