SCEC Award Number 13071 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Transient Detection using PBO data with contributions to the CGM.
Name Organization
Thomas Herring Massachusetts Institute of Technology
Other Participants Mike Floyd, Kang Hyeun Ji
SCEC Priorities 5, 1, 1 SCEC Groups Transient Detection, Geodesy, SDOT
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
We are undertaking two main tasks in this SCEC grant: (1) Development of transient signal detection methods and (2) analyses for the Community Geodetic Model (CGM). For the transient detection development we have submitted our algorithms to the Colaboratory for the Study of Earthquake Predictability (CSEP) and they are now running operationally. For the CGM contribution we are continuing analyses of functional or physical parameters associated with time-dependent motions in southern California and to begin action towards data collation for the CGM.
We contributed to a first geodetic publication on the El Mayor-Cucapah earthquake using survey data from within Mexico (Gonzalez-Ortega et al., 2014). The data used for this have also been collected, verified and processed here for further analysis through physical modeling. This allows long-term background motions to be better known, from which superimposed transient events may be detected even in the presence of post-seismic motion. Furthermore, the handling of these survey data demonstrates the necessary action required moving forward with the CGM.
In anticipation of the CGM reaching beyond the simple presentation of geodetic velocities to some form of kinematic model, and following the work of Smith-Konter et al. (2011), we have approached the problem of relatively shallow geodetically-derived fault locking depths and their appropriate interpretation within the framework of the earthquake cycle and recurrence times. This work explores conditions under which that velocity profiles across faults invert to give shallow locking depths using the common Savage and Burford (1973) formulation, despite synthetic input having slip deficit accumulate that estimated depth. We suggest that direct interpretation may lead to moment accumulation rate being underestimated and recurrence times being overestimated (by up to a factor of two) in cases where the fault does not behave in the simple, homogeneous, fully-locked manner described by this model.
Intellectual Merit Our research is contributing to the transient signal detection and the development of the Community Geodetic Model. These activities are targeted at developing an understanding of the complex deformation modes California and the relationship of this deformation to earthquake occurrence.
Broader Impacts The accurate modeling of post-seismic motions surrounding the 2010-04-04 El Mayor-Cucapah earthquake has profound implications in two key areas.
First, regarding this research specifically, short-period transient motions may not be confidently detected if longer term motions are not adequately known, especially in the presence of time-variable motions. The proximity of several creeping faults in the Imperial Valley and geothermal sources such as the Salton Sea north of the US-Mexico border and Cerro Prieto south of the border must be determined within the framework of the broader time-dependent motions in the aftermath of the El Mayor-Cucapah earthquake.
Second, more generally, the El Mayor-Cucapah earthquake represents a unique perspective on post-seismic motions in a region of tectonic transition, from pure strike-slip in the north to that with an increasing component of extension in the south, combined with a thinner crust and higher geothermal gradient. The relaxation and dispersion of stresses induced by the earthquake over time must continue to be measured and analysed to understand how the stresses on faults to the north of the rupture’s termination are changing and whether this may promote or inhibit future rupture initiation in those areas.
Both areas of research contribute to our understanding of and eventual ability to monitor crustal motions in California in real-time or near real-time. The project continues to engage and foster close collaborations our community’s neighbors in Mexico.
Exemplary Figure Figure 1