Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Wilkins, S. J. Articles by Schultz, R. A. Search for Related Content GeoRef GeoRef Citation

3D Cohesive End-Zone Model for Source Scaling of Strike-Slip Interplate Earthquakes

¹ Geomechanics-Rock Fracture Group
Department of Geological Sciences and Engineering
Mackay School of Earth Sciences and Engineering (172)
University of Nevada
Reno, Nevada 89557-0138

Correspondence: ^* Present address: Structure, Traps, and Seals Team, Shell International Exploration & Production Inc., Bellaire Technology Center, P.O. Box 481, Houston, Texas 77001-0481. Scott.Wilkins{at}Shell.com

A 3D, static fracture mechanics model of earthquake rupture that incorporates cohesive end zones (CEZs), or zones of increased frictional strength, is tested to determine whether it helps to understand the observed scaling behavior of average slip with rupture dimensions for shallow (<20 km), continental, interplate strike-slip earthquakes. Our new compilation of average source parameters suggests that (1) average slip increases with aspect ratio (along-strike length/down-dip width), although in decreasing proportions for progressively larger aspect ratio ruptures, and (2) a gradual scaling change exists at an aspect ratio of 6. These general trends match the functional form predicted by the CEZ model. Despite these general trends, significant scatter in average slip is apparent among similarly sized ruptures. We test the hypothesis that the CEZs represent strength heterogeneities along the rupture surface that result from velocity-strengthening frictional behavior; and that this heterogeneity in frictional behavior along the fault is the primary reason for the failure of a universal (constant stress drop) scaling law. CEZ lengths are measured from slip and stress drop distributions determined from published inversions of geophysical data for the 1984 Morgan Hill, 1992 Landers, 1999 Hector Mine, and 1999 zmit earthquakes, and range from 15 to 40% of the rupture segment lengths. These lengths are an order of magnitude larger than that inferred from characteristics of high-frequency seismic radiation (i.e., f_max). These data indicate that the ratio of average coseismic slip to rupture length decreases in the presence of large CEZs. Measured CEZ lengths, rupture dimensions, and average slip are used to calculate average resolved shear-driving stresses and CEZ shear-yield strengths on the order of 10–30 MPa. In our new model of earthquake rupture, stress drop is predicted to be a small fraction of fault strength and thus supports a partial stress drop model of earthquake rupture for strike-slip interplate events.

This article has been cited by other articles:

				P. J. Lovely, D. D. Pollard, and O. Mutlu Regions of Reduced Static Stress Drop near Fault Tips for Large Strike-Slip Earthquakes Bulletin of the Seismological Society of America, June 1, 2009; 99(3): 1691 - 1704. [Abstract] [Full Text] [PDF]