Project Abstract
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Quantifying transient tectonic signals continues to reveal new insights into fault behavior and crust/mantle rheology [Segall and Matthews, 1997; McGuire and Segall, 2003; Freed and Bürgmann, 2004; Ji and Herring, 2013]. Through previous SCEC funding we have developed, tested, and automated a geodetic network processing system for detection of anomalous strain transients in Southern California [Holt and Shcherbenko, 2013]. These codes are now being incorporated into the Collaboratory for the Study of Earthquake Predictability (CSEP). The modeling procedure determines time-dependent displacement gradient fields from continuous GPS (cGPS) time series [Hernandez et al., 2005, 2007; Holt and Shcherbenko, 2013]. The method has been tested using the SCEC IV Transient Detection Exercise and is able to recover the spatial and temporal distribution of slow events and determine their statistical significance. To date we have detected several transient strain phenomena within southern California. We show that these anomalous strains have occurred on a variety of time scales, they involve heterogeneous distributions, and they have impacted stress rates and coulomb stress changes on faults [Shcherbenko, 2014; Shcherbenko and Holt, 2015]. Current efforts are showing promise for quantifying links between measured strain changes, model stress changes, and seismicity rates. We applied the network processing tool in northern California where seasonal transient strains prior to the 2014 South Napa earthquake show a focused anomally within the South Napa region [Kraner and Holt., 2015, Kraner et al., 2016]. Using our time-dependent measurements obtained from the geodetic network processing tool [Holt and Shcherbenko, 2013] we are currently developing a data product that will enable the tracking of strain and stress change evolution, along with expected seismicity rate evolution through time. The work performed to date fulfills the SCEC Science Objective 5b “Application of geodetic detectors to the search for aseismic transients across southern California” and also supports 2c, 1d, and 1e and 2d. Moreover, this research fulfills the recommendations under Research Strategies in Tectonic Geodesy to: (a) “Improve our understanding of the processes underlying detected transient deformation signals and/or their seismic hazard implications through data collection and development of new analysis tools.” |
