SCEC Award Number 12074 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Temporal changes of earthquake rate and seismic velocity in southern California following the 2010 M7.2 El Mayor-Cucapah Earthquake
Name Organization
Zhigang Peng Georgia Institute of Technology
Other Participants Xiaofeng Meng (Georgia Tech)
SCEC Priorities 2b, 2a, 2f SCEC Groups Seismology, FARM, EFP
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
We conducted a systematic detection of missing earthquakes in Southern California following the El Mayor-Cucapah mainshock (Meng et al., 2012, 2013). By running the detection algorithm in parallel GPU settings, we can achieve several hundred times faster speed than running the job in standard desktop CPUs. So far we have detected about 80 times more earthquakes than listed in the SCSN catalog. The obtained seismicity rate changes suggest a clear increase of seismic activity in many regions, including those in stress shadows. However, the seismicity rates correlate better with static stress changes a few months later. These results suggested that dynamic stress changes dominant in the short-term, while static stress changes play a more important role at later time.
Intellectual Merit This project is a continuation of a previously funded SCEC project “Testing static vs dynamic triggering in southern California after the 2010 M7.2 El Mayor-Cucapah Earthquake”. Our project is directly relevant to the science priorities for the Seismology Disciplinary Activities in 2012 on the “The 2010 M7.2 El Mayor-Cucapah Earthquake Sequence.”. In addition, it addresses the following Fundamental Problems in Earthquake Physics as outlined in the SCEC4 RFP: (1) 2a “Improvement of earthquake catalogs …”; and 2b “Improved description of triggered earthquakes”. If successful, our proposed work could help to contribute to the aforementioned debate on static vs. dynamic triggering of aftershocks and triggered seismicity
Broader Impacts This project provided a partial support for the GT graduate student Xiaofeng Meng, who is expected to finish his Ph.D. in May 2014. Xiaofeng has become an expert in this topic, as evident by several manuscripts published or submitted over the last two years. The results from this project will become a major component of his Ph.D. thesis. This project also provided a partial support for a summer intern Stephen Allam (Randough College undergraduate student) in summer 2012. Stephen worked together with Xiaofeng on detecting missing aftershocks following the 2011 Mw5.8 Virginia earthquake [Allam et al., 2012]. We have started working with Professor Kim Olsen’s group at SDSU to use realistic rupture models for accurate estimations of both dynamic and static stress changes at many regions and compare with seismicity patterns [Meng et al., 2013]. We plan to release our detected catalogs and the computation code via peer-reviewed publications.
Exemplary Figure Figure 3. Seismicity rate changes near the Salton Sea geothermal field (SSGF). (a) and (b) CC and magnitude of detected events versus days relative to the mainshock, respectively. (c) Number of events detected per day. The green shaded areas mark data gaps in continuous data. The vertical dashed lines mark two time windows, T1 and T2, from which β values are computed in (e) and (f). The blue curve shows the cumulative number of detected events. The red dashed line denotes the approximate pre-shock rate. (d) Number of events listed in the relocated catalog per day. The blue curve shows the cumulative number of events. (e) and (f) β values versus cutoff magnitude and CC for two time windows, respectively. The horizontal dashed lines denote the 95% confidence level of significant seismicity rate increase and decrease, respectively.