SCEC Award Number 18014 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Multidisciplinary exploration for slow aseismic slip and low-frequency earthquakes in the Anza Gap (San Jacinto fault zone)
Investigator(s)
Name Organization
William Frank University of Southern California Roland Bürgmann University of California, Berkeley
Other Participants Baptiste Rousset (postdoc @ UC Berkeley)
Master's student (USC)
SCEC Priorities 1a, 2a, 1e SCEC Groups FARM, Geodesy, SDOT
Report Due Date 03/15/2019 Date Report Submitted 04/30/2019
Project Abstract
 We used a multidisciplinary approach to systematically search for slow aseismic transient slip in the Anza Gap of the San Jacinto fault zone using continuous geodetic and seismic datasets. The spatial and temporal distribution and evolution of aseismic transients is essential information to understand whether longterm tectonic strain in the Anza Gap is building up to a future large (M > 7) earthquake, or if a significant amount of strain is released aseismically. Recent work has identified both aseismic transients and triggered tectonic tremor in the Anza Gap following significant regional and local earthquakes [Chao et al.,2012; Wang et al., 2013; Inbal et al., 2017]. We build on these studies by independently searching in the continuous geodetic data for slow slip and in the continuous seismic data for low-frequency earthquakes, the principal constituent of tectonic tremor.
Intellectual Merit By searching for transient deformation signals both on seismic and geodetic continuous records, this study aims at better characterizing the spatio-temporal variations of slip and stress on faults, and particularly on the Anza segment of the San Jacinto fault. The spatial and temporal distribution and evolution of aseismic transients is essential information to understand whether long-term tectonic strain in the Anza Gap is building up to a future large (M > 7) earthquake, or if a significant amount of strain is released aseismically.
Broader Impacts The project provided support for a master student at USC. She is now a PhD student at Universität Bern (although no longer in seismology…).
Exemplary Figure Figure 3: Repeats of the low-frequency earthquake (LFE) triggered by the 2002 Denali Earthquake, identified by Wang et al. [2013], and its time-reversed copy. The recurrence intervals are measured as the time between sequential repeats. The time-reversed waveforms were used to establish what threshold should be used to minimize the number of false detections (false positives). The dashed line indicates the timing of the 2002 Denali Earthquake. Clustered activity (short recurrence intervals) is a characteristic feature of LFEs [Frank et al., 2016], but is not observed here.