SCEC Award Number 14175 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Improved understanding of moderate-size earthquake sequences on the San Jacinto Fault and their relationship with deep creep
Investigator(s)
Name Organization
Zhigang Peng Georgia Institute of Technology
Other Participants Xiaofeng Meng
SCEC Priorities 2a, 2b, 2c SCEC Groups Seismology, FARM, SDOT
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
 We systematically analyze spatio-temporal evolutions of 10 M>4 earthquakes along the San Jacinto Fault near the Anza gap since 2000, by applying a recently matched filter technique [Meng and Peng, 2014a]. We detecte at least 4 times more events than listed in the SCSN catalog for all sequences. We then compare the sizes of aftershock zones among 6 sequences with clear aftershock zones. The 3 events that iniated in the deeper part (> 12 km) of the seismogenic zone (i.e., 2001 M5.1, 2005 M5.2 and 2010 M5.4) all have abnormally long aftershock zone along the SJF. The 2002 M4.2 and 2013 M4.7 event, which are ~12 km in depth, have smaller aftershock zones. The 2010 M4.9 event, with a hypocentral depth of 9 km, has the smallest aftershock zone. The sharp contrast in the lengths of aftershock zones for shallow and deep earthquakes supports the hypothesis that deep creep along the SJF may present and drive the aftershock sequences for deep events.
Intellectual Merit Our continued research in this direction helps to improved earthquake catalogs in southern California by using the innovative matched filter technique. The newly detected catalogs can be used by us and others to improve our understanding of stress-mediated fault interactions and earthquake clustering.
Broader Impacts We shared our newly detected catalogs to Caltech group, and via peer-reviewed publication (Meng and Peng, GJI, 2014). In addition, we are in the process of developing an online tutorial on triggering and detection, that will be shared to the public soon. An draft version can be found at
http://geophysics.eas.gatech.edu/people/zpeng/Teaching/Triggering_Tutorial/
Exemplary Figure Figure 2. (Left) The cross-section view of the SJF around the hypocenters of moderate earthquakes. Dots denote aftershocks, which are color coded by their origin times and scaled by their magnitudes. The horizontal bars denote the β-values (black β<2; red β>2). The vertical grey lines denote the defined aftershock zone. (Right) The histogram of depth distribution of aftershocks. The horizontal red line denotes the depth of the mainshock.
Linked Publications

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  • Peng, Z., & Meng, X. (2015). Increasing lengths of aftershock zones with depths of moderate-size earthquakes on the San Jacinto Fault suggests triggering of deep creep in the middle crust. Geophysical Journal International, 204(1), 250-261. SCEC Contribution Number 6179