Response of seismicity to static and dynamic stress changes induced by the 2011 M9.0 Tohoku-Oki earthquake
Abstract
A growing body of evidence indicates that many earthquakes are triggered by static and dynamic stress changes following large earthquakes. However, it has been difficult to differentiate the roles of static and dynamic stress transfer on earthquake triggering. Here we focus on two adjacent seismic clusters aligned E-W beneath the Hida mountain range, central Japan, where spatially uniform static and dynamic stress changes resulted from Tohoku-Oki earthquake. A detailed analysis of the seismicity would provide us with a unique opportunity to differentiate the effects of static and dynamic stress transfer on earthquake triggering. To improve on the precision of seismicity in the JMA catalogue, we applied a matched-filter technique to continuous seismograms recorded by a dense and highly sensitive seismic network. We evaluated the completeness magnitude threshold Mc of the newly detected events, and we discuss the temporal changes of seismicity rate in the Hida mountain range before and after the Tohoku-Oki earthquake, as well as assess the relative contributions of static and dynamic stress transfers to earthquake triggering. In the western cluster, the cumulative number showed no abrupt change coincident with the Tohoku-Oki earthquake, but it showed a slight increase over the three days following the event. Based on the laboratory-based rate/state constitutive law, the static Coulomb stress change of ~0.02 MPa induced by the Tohoku-Oki earthquake on the studied area could raise the seismicity rate by several factors. This relatively small increase in the seismicity rate is roughly consistent with the slightly increased seismicity observed in the western cluster. Thus, the static stress transfer to the Hida mountain range is a plausible triggering mechanism in the western cluster. In contrast, the rate of triggered events in the eastern cluster is remarkably higher than that in the western cluster. The seismicity rate in the eastern cluster increased more than 104-fold, relative to the measured background rate (~0.03 day-1). This marked change in the seismicity rate is difficult to explain solely in terms of the small static stress step of ~0.02 MPa and the conventional frictional values. Of note, the initial detected event in the eastern cluster following the Tohoku-Oki earthquake was triggered during the passage of surface waves. We therefore consider that the dynamic stress is a plausible triggering mechanism in the eastern cluster. The small increase in seismicity rate in the western cluster may indicate that the intensive activity prior to the Tohoku-Oki earthquake had already expended the seismic energy at the sites of potential earthquake-nucleation patches. In such a case, the dynamic stress change would have been unlikely to trigger abundant events at remote distances from the source rupture. In contrast, the eastern cluster may have been the site of many large-sized potential earthquake-nucleation patches close to a state of failure, because there had been no significant activity in the area of the eastern cluster during the 7-8 years prior to the Tohoku-Oki earthquake. Preparedness for failure in earthquake patches is an important prerequisite for remote triggering by surface waves. Monitoring earthquakes using dense seismic network such as MeSO-net and Hi-net is a powerful tool to understand earthquake interaction.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.S44B..07K
- Keywords:
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- 7209 SEISMOLOGY Earthquake dynamics;
- 7230 SEISMOLOGY Seismicity and tectonics;
- 7223 SEISMOLOGY Earthquake interaction;
- forecasting;
- and prediction;
- 8163 TECTONOPHYSICS Rheology and friction of fault zones