HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) References 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 LEVANDER, A. R. Articles by KOVACH, R. L. Search for Related Content GeoRef GeoRef Citation

S-wave observations in the Franciscan terrane, central California

DEPARTMENT OF GEOPHYSICS STANFORD UNIVERSITY, STANFORD, CALIFORNIA 94305

Abstract

We have examined S-wave arrivals from local earthquakes at a three-station seismograph array in the Franciscan terrane of the Diablo Range, California. A single crustal S-wave phase is observed with a velocity of 3.30 km/sec. Poisson's ratio calculated for the crust from a composite Wadati diagram is 0.27. Beyond epicentral distances of 90 km we have tentatively identified an Sn phase with a velocity of 4.35 km/sec. Other investigators have reported a Pn velocity of 8.0 km/sec corresponding to an upper mantle Poisson's ratio of 0.29.

The 3.30 km/sec crustal S-wave velocity is intermediate in value between crustal S-wave velocities measured in similar terranes 75 km north at Berkeley and 90 km south at Bear Valley, suggesting a NW-SE crustal S-wave velocity gradient east of the San Andreas fault in the Franciscan terrane. This may be indicative of an increase in crustal rigidity from southeast to northwest, possibly associated with the differing levels of seismic activity observed along portions of the San Andreas fault.

This article has been cited by other articles:

				W. H. BAKUN and W. B. JOYNER The ML scale in central California Bulletin of the Seismological Society of America, October 1, 1984; 74(5): 1827 - 1843. [Abstract] [PDF]

				A. R. LEVANDER, H. QUIN, and R. L. KOVACH Shear wave observations in the region north of the San Francisco Bay Bulletin of the Seismological Society of America, August 1, 1983; 73(4): 1031 - 1039. [Abstract] [PDF]

				A. W. WALTER and W. D. MOONEY Crustal structure of the Diablo and Gabilan Ranges, central California: A reinterpretation of existing data Bulletin of the Seismological Society of America, October 1, 1982; 72(5): 1567 - 1590. [Abstract] [PDF]