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A detailed, automatically-derived, seismicity catalog for the San Jacinto fault zone (1998-2016)

Malcolm C. White, Zachary E. Ross, Yehuda Ben-Zion, & Frank L. Vernon

Published August 12, 2017, SCEC Contribution #7529, 2017 SCEC Annual Meeting Poster #072

Earthquake catalogs of provide foundational datasets for numerous studies on earthquake physics, dynamics of seismicity, fault structure at depth, tomography, stress inversions and seismic hazard analysis. The San Jacinto fault zone is the most seismically active structure in southern California and has sustained at least 15 major ruptures (Mw > 7) in the past 4, 000 years, with a recurrence interval of ~254 years. It is a densely-instrumented portion of the plate-boundary in southern California, with data from mature local and regional networks and several recent near-fault deployments. The available data sets are combined to form a virtual network around the San Jacinto fault zone and are processed ab initio to produce a detailed catalog (spanning 1998 through 2016) of hypocenter parameters, earthquake magnitudes and P/S-wave arrival observations for > 155, 000 events.

A P to S wave observation ratio of approximately 3:2 is achieved by applying a polarization filter to increase the signal-to-noise ratio of S-wave energy before applying statistical detectors. Hypocenters are determined with an eikonal-based ray tracer and a 3D velocity model derived from body-wave/surface-wave joint inversion tomography. Double-difference relocations are obtained for > 77, 000 events, removing some of the path effects resulting from unknown velocity structure along ray paths common among neighbouring events. Finally, local magnitudes (ML) are estimated from amplitude measurements and moment magnitudes (MW) are calculated from the potency estimated with spectral analysis.

The large volume of analyzed data necessitates automatic processing techniques that have the added benefits of consistency and objectivity of processing. The combined consistency and volume of the catalog provide a product highly suitable for large-scale statistical analyses. Confidence in the catalog is calibrated by comparison with 1,036 manually analyzed events over a 40-day period. Statistical and structural features of the observed seismicity and comparisons with existing catalogs will be presented at the meeting.

White, M. C., Ross, Z. E., Ben-Zion, Y., & Vernon, F. L. (2017, 08). A detailed, automatically-derived, seismicity catalog for the San Jacinto fault zone (1998-2016). Poster Presentation at 2017 SCEC Annual Meeting.

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