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WITHDRAWN Anatomy of a Fault Zone: Space-Time-Magnitude Patterns of Microseismicity in the San Jacinto Fault Zone, Southern California

Description: 

WITHDRAWN We present key space-time-magnitude patterns of microseismicity observed in an updated catalog for the San Jacinto Fault Zone (SJFZ)—the most seismically active region in Southern California—during the period 2008-2022. We deploy an automated procedure to process raw waveform data from five seismic networks and capture a more complete representation of the space-time-magnitude distribution of events in the SJFZ than the standard catalog for the region. Seismicity patterns in our new catalog delineate the geometry of the locked region of the fault and the brittle-to-ductile transition zone (BDTZ)—features bearing important implications on the maximum potential magnitude of future ruptures in the area. Spatiotemporally diffuse seismicity characterizes semi-brittle deformation in the BDTZ, in contradistinction to the tightly clustered nature of seismicity in the overlying brittle crust. We observe transient clustering of seismicity in the BDTZ following some, but not all, moderate-sized events (M>4.5) in the region. Our high-definition catalog also helps constrain complex internal geometry of fault zone structures such as (1) anastamosing braids of deep seismicity in the Hot Springs Area; (2) conjugate networks of shallow fractures flanking the core fault zone; (3) the extent of the Anza Seismic Gap; and (4) branching structures in the Trifurcation Region. We will present an overview of these features and plans to further improve the SJFZ catalog using new tools.

Session: Deciphering Earthquake Clustering for the Better Understanding of Crustal Deformation Mechanisms

Type: Oral

Date: 4/20/2023

Presentation Time: 03:00 PM (local time)

Presenting Author: Malcolm C. A. White

Student Presenter: No

Invited Presentation: 

Authors