Quick Search:    advanced search

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

This Article Full Text (PDF) References 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 Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by WEBB, T. H. Articles by KANAMORI, H. Search for Related Content GeoRef GeoRef Citation

Earthquake focal mechanisms in the Eastern Transverse Ranges and San Emigdio Mountains, Southern California and evidence for a regional decollement

SEISMOLOGICAL LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, CALIFORNIA 91125
GEOPHYSICS DIVISION D.S.I.R., P.O. BOX 1320, WELLINGTON, New Zealand

Abstract

Earthquake focal mechanisms obtained from P-wave first motions are presented for the Eastern Transverse Ranges and the San Emigdio Mountains in Southern California. The former region shows a predominance of strike-slip faulting whereas Quaternary faults in the region show thrust motion. We suggest that the observed strike-slip mode of deformation cannot continue indefinitely without the occurrence of more thrust faulting. Fault deformation in the San Emigdio Mountains inferred from focal mechanisms is in accord with displacements across Quaternary faults in the area. This study and a search of the literature has yielded 19 mechanisms with shallow-dipping nodal planes. Previous workers have interpreted such mechanisms as evidence for a regional decollement. If such a regional decollement exists, these data give some indication of its regional extent. Slip directions inferred from the focal mechanisms with shallow-dipping nodal planes show some regional consistency, but this pattern cannot be entirely explained with current tectonic models. A comparison of the stress drop of an event having a shallow-dipping nodal plane with an event with steeper planes gave inconclusive results.

Footnotes

^* Present address: Geophysics Division, DSIR, P.O. Box 1320, Wellington, New Zealand.

This article has been cited by other articles:

				E. S. Nemser and D. S. Cowan Downdip segmentation of strike-slip fault zones in the brittle crust Geology, May 1, 2009; 37(5): 419 - 422. [Abstract] [Full Text] [PDF]

				V.E. Langenheim, R.C. Jachens, J.C. Matti, E. Hauksson, D.M. Morton, and A. Christensen Geophysical evidence for wedging in the San Gorgonio Pass structural knot, southern San Andreas fault zone, southern California Geological Society of America Bulletin, November 1, 2005; 117(11-12): 1554 - 1572. [Abstract] [Full Text] [PDF]

				C. Nicholson Seismic behavior of the southern San Andreas fault zone in the northern Coachella Valley, California: Comparison of the 1948 and 1986 earthquake sequences Bulletin of the Seismological Society of America, October 1, 1996; 86(5): 1331 - 1349. [Abstract] [PDF]

				G. J. Huftile and R. S. Yeats Deformation rates across the Placerita (Northridge Mw = 6.7 aftershock zone) and Hopper Canyon segments of the western transverse ranges deformation belt Bulletin of the Seismological Society of America, February 1, 1996; 86(1B): S3 - S18. [Abstract] [PDF]

				C. J. AMMON and G. ZANDT Receiver structure beneath the southern Mojave Block, California Bulletin of the Seismological Society of America, June 1, 1993; 83(3): 737 - 755. [Abstract] [PDF]

				F. F. POLLITZ and I. S. SACKS Modeling of postseismic relaxation following the great 1857 earthquake, southern California Bulletin of the Seismological Society of America, February 1, 1992; 82(1): 454 - 480. [Abstract] [PDF]

				J. PACHECO and J. NABeLEK Source mechanisms of three moderate California earthquakes of July 1986 Bulletin of the Seismological Society of America, December 1, 1988; 78(6): 1907 - 1929. [Abstract] [PDF]

				M. D. Zoback, M. D. ZOBACK, M. L. ZOBACK, V. S. MOUNT, J. SUPPE, J. P. EATON, J. H. HEALY, D. OPPENHEIMER, P. REASENBERG, L. JONES, et al. New Evidence on the State of Stress of the San Andreas Fault System Science, November 20, 1987; 238(4830): 1105 - 1111. [Abstract] [PDF]

				J. H. MCBRIDE and L. D. BROWN Reanalysis of the cocorp deep seismic reflection profile across the San Andreas fault, Parkfield, California Bulletin of the Seismological Society of America, December 1, 1986; 76(6): 1668 - 1686. [Abstract] [PDF]

				L. M. JONES, L. K. HUTTON, D. D. GIVEN, and C. R. ALLEN The North Palm Springs, California, earthquake sequence of July 1986 Bulletin of the Seismological Society of America, December 1, 1986; 76(6): 1830 - 1837. [PDF]