Kaneko, Y. and Lapusta, N. and Ampuero, J.-P. (2008) Spectral-element modeling of spontaneous earthquake rupture on rate and state faults: Effect of velocity-strengthening friction at shallow depths. Journal of Geophysical Research B, 113 (B9). Art. No. B09317. ISSN 0148-0227. http://resolver.caltech.edu/CaltechSOLIDS:2008.001
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We develop a spectral-element methodology (SEM) for simulating dynamic rupture on rate and state faults and use it to study how the rupture is affected by a shallow fault region of steady-state velocity-strengthening friction. Our comparison of the developed SEM and a spectral boundary-integral method (BIM) for an anti-plane (two-dimensional) test problem shows that the two methods produce virtually identical solutions for the finest resolution we use and that the convergence with grid reduction of the developed SEM methodology is comparable to that of BIM. We also use the test problem to compare numerical resolution required for different state evolution laws and for linear slip-weakening friction. Using our three-dimensional implementation of the methodology, we find that a shallow velocity-strengthening fault region can significantly alter dynamic rupture and ground motion. The velocity-strengthening region suppresses supershear propagation at the free surface occurring in the absence of such region, which could explain the lack of universally observed supershear rupture near the free surface. In addition, the velocity-strengthening region promotes faster fall-off of slip velocity behind the rupture front and decreases final slip throughout the entire fault, causing a smaller average stress drop. The slip decrease is largest in the shallow parts of the fault, resulting in the depth profile of slip qualitatively consistent with observations of shallow co-seismic slip deficit. The shallow velocity-strengthening region also reduces the amplification of strong ground motion due to a low-velocity bulk structure.
|Additional Information:||© 2008 American Geophysical Union. Received 17 December 2007; revised 2 June 2008; accepted 11 June 2008; published 27 September 2008. The authors thank Tom Heaton, Qinya Liu, and Yi Liu for helpful discussions. The reviews by Eric Dunham, Gaetano Festa, and an anonymous reviewer helped us improve the manuscript. We thank Eric Dunham for providing us with the unpublished functional form of the rupture initial procedure. Nadia Lapusta gratefully acknowledges the support of the National Science Foundation (grant EAR 0548277) and the Southern California Earthquake Center. SCEC is funded by NSF Cooperative Agreement EAR-0106924 and USGS Cooperative Agreement 02HQAG0008. Jean-Paul Ampuero was supported by SPICE, a Marie Curie Research and Training Network in the 6th Framework Program of the European Commission. The numerical simulations for this research were performed on Caltech Division of Geological and Planetary Sciences Dell cluster. This is SCEC contribution 1203.|
|Group:||Solid Mechanics Research Group, Seismological Laboratory|
|Subject Keywords:||spectral element method; rate and state friction; rupture dynamics|
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|Official Citation:||Kaneko, Y., N. Lapusta, and J.-P. Ampuero (2008), Spectral element modeling of spontaneous earthquake rupture on rate and state faults: Effect of velocity-strengthening friction at shallow depths, J. Geophys. Res., 113, B09317, doi:10.1029/2007JB005553.|
|Usage Policy:||You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format.|
|Deposited By:||Imported from CaltechSOLIDS|
|Deposited On:||30 Jan 2008|
|Last Modified:||17 Sep 2015 22:41|
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