Postseismic Relaxation Along the San Andreas Fault at Parkfield from Continuous Seismological Observations

Abstract

Seismic velocity changes and nonvolcanic tremor activity in the Parkfield area in California reveal that large earthquakes induce long-term perturbations of crustal properties in the San Andreas fault zone. The 2003 San Simeon and 2004 Parkfield earthquakes both reduced seismic velocities that were measured from correlations of the ambient seismic noise and induced an increased nonvolcanic tremor activity along the San Andreas fault. After the Parkfield earthquake, velocity reduction and nonvolcanic tremor activity remained elevated for more than 3 years and decayed over time, similarly to afterslip derived from GPS (Global Positioning System) measurements. These observations suggest that the seismic velocity changes are related to co-seismic damage in the shallow layers and to deep co-seismic stress change and postseismic stress relaxation within the San Andreas fault zone.

Monitoring of environmental influences on seismic velocity at the geological storage site for CO2 in Ketzin (Germany) with ambient seismic noise

“…Temporal changes have been successfully detected directly after large earthquakes as a sudden drop in seismic velocity and a slow recovery afterwards (Brenguier et al 2008a;Wegler et al 2009;Richter et al 2014). Monitoring of active volcanoes showed a drop in seismic velocity before eruptions (Brenguier et al 2008b;Sens-Schönfelder et al 2014).…”

Field observations of seismic velocity changes caused by shaking-induced damage and healing due to mesoscopic nonlinearity

“…With data from a very dry region in Chile, Richter et al (2014) derived a model for the annual variations based on thermally induced stress described in more detail in Section 3.1.1. Velocity drops after large earthquakes followed by a slow recovery were detected by Rubinstein & Beroza (2004a), Li et al (2007), Brenguier et al (2008a), Wegler et al (2009), Nakata & Snieder (2011), Takagi et al (2012), Hobiger et al (2012), Richter et al (2014) and other authors. In particular, Richter et al (2014) showed that the amplitude of the velocity drop after an earthquake is proportional to the local peak ground acceleration (pga).…”

Extreme hydrothermal conditions at an active plate-bounding fault

“…1). Borehole injection experiments, earthquake aftershock studies, and laboratory experiments on fault zone materials reveal that the earthquake process perturbs the fault zone, which then heals during the post-seismic period [22][23][24][25][26] .…”