global Search of Triggered Tremor and Low-Frequency Earthquakes

global Search of Triggered Tremor and Low-Frequency Earthquakes A comparison of surface waves of large teleseismic earthquakes and triggered tremor beneath (a) Vancouver Island in British Columbia [Rubinstein et al., 2007], (b) the Central Range in Taiwan [Peng and Chao, 2008], (c) the San Andreas Fault in Central California [Peng et al., 2009], and (d) the subduction zone is Southwest Japan [Miyazawa et al., 2008]. The traces have been time-shifted to reflect the relationship between the surface waves and tremor at the source region.
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Deep “non-volcanic” tremor and episodic slow-slip events are among the most interesting discoveries in earthquake seismology in the last decade. These events have much longer source durations than regular earthquakes, and are generally located near or below the seismogenic zone where regular earthquakes occur. Tremor and slow-slip events appear to be extremely stress sensitive, and could be instantaneously triggered by distant earthquakes and solid earth tides. We have conducted a global search of triggered tremor and low-frequency earthquakes (LFEs) associated with large regional and teleseismic earthquakes. These include the Parkfield-Cholame section of the San Andreas Fault [Gomberg et al., 2008; Peng et al., 2009], the Calaveras fault in northern California and the San Jacinto Fault in southern California [Gomberg et al., 2008], and beneath the Central Range in Taiwan [Peng and Chao, 2008]. In several places, we found that tremor is often initiated by the Love waves, and continues to be modulated during the subsequent Rayleigh waves. Many LFEs were identified during the triggered tremor episode, and triggered LFEs sometimes showed fast migrations along the fault strike, similar to ambient LFEs/tremor and possibly reflecting triggered micro-slow-slip events. Long-period and large-amplitude surface waves from both regional and teleseismic events have a greater potential of triggering tremor, and inferred triggering threshold is on the order of ~1kPa, suggesting that the deep faults are critically stressed, most likely due to near-lithostatic fluid pressures.
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References
</p><p>Gomberg, J., J. L. Rubinstein, Z. Peng, K. C. Creager, and J. E. Vidale (2008), Widespread triggering of non-volcanic tremor in California, Science, 319, 173.
</p><p>Peng, Z., and K. Chao (2008), Non-volcanic tremor beneath the Central Range in Taiwan triggered by the 2001 Mw7.8 Kunlun earthquake, Geophys. J. Int. (Fast track), 825, 829.
</p><p>Peng, Z., J. E. Vidale, A. Wech, R. M. Nadeau and K. C. Creager (2009), Remote triggering of tremor along the San Andreas fault in central California, J. Geophys. Res., 114, B00A06.
</p><p>Acknowledgements: This work was supported by the National Science Foundation (EAR-0809834, EAR-0956051).</p>

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