Complex Dynamics of Seismic Bursts in Southern California: Is Radial Localization a Signature of Increasing Regional Tectonic Stress?

Session: Crustal Stress and Strain and Implications for Fault Interaction and Slip
Type: Oral
Date: 4/28/2020
Time: 11:30 AM
Room: 240
Description: 

We present a method to analyze the dynamics of seismic bursts in the Southern California region. Our analysis considers seismic bursts to be sequences of small earthquakes strongly clustered in space and time. Examples of bursts are swarms and aftershocks. In the Southern California earthquake catalog, we identify hundreds of these potentially coherent space-time structures in a region defined by a circle of radius 600 km around Los Angeles. We compute the radius of gyration (RG) of each cluster, then filter them to identify those bursts with large numbers of events closely clustered in space ("compact" bursts). Our basic assumption is that these compact bursts reflect the dynamics associated with large earthquakes. Once we have filtered the burst catalog, we a time series for the Southern California region. We observe that the RGs of these bursts systematically decrease prior to large earthquakes, in a process that we might term "radial localization". RGs rapidly increase during an aftershock sequence and a new cycle of radial localization then begins. These time series display cycles of recharge and discharge reminiscent of seismic stress accumulation and release that have been hypothesized to occur during the elastic rebound process. The complex burst dynamics we observe are evidently a property of the region as a whole, rather than being associated with individual faults, as is true of many complex systems.

Presenting Author: John B. Rundle

Authors