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Deep Tremor Activities beneath the Central Range in Taiwan and their Relationship to Local, Regional, and Teleseismic Earthquakes

CHAO, K., Georgia Institute of Technology, Atlanta, GA, kevinchao@gatech.edu; PENG, Z., Georgia Institute of Technology, Atlanta, GA, zpeng@gatech.edu; WECH, A., Victoria University of Wellington, Wellington, New Zealand, Aaron.Wech@vuw.ac.nz; TANG, C., National Chung Cheng University, Chia-Yi, Taiwan, iori897@gmail.com; LIN, C., Academia Sinica, Taipei, Taiwan, lin@earth.sinica.edu.tw; CHEN, C., National Chung Cheng University, Chia-Yi, Taiwan, seichen@eq.ccu.edu.tw

Deep “non-volcanic” tremor has been observed at many major plate-boundary faults, which provides new information about fault slip behaviors below the seismogenic zone. Several studies have shown that large earthquakes at regional and teleseismic distances can trigger tremor activity. However, it is not clear whether tremor precedes large earthquakes or tremor triggered by distant earthquakes leads to other local earthquakes. Here we conducted a systematic analysis of tremor activity beneath the southern Central Range of Taiwan one month before and after the 03/04/2010 M6.4 Jiasian earthquake. The study period is chosen mainly because the hypocenter of the Jiasian event was located at the southwest (~30 km away) of the triggered tremor sources identified from our previous studies. In addition, the 02/27/2010 Mw8.8 Chile earthquake occurred a few days before the Jiasian event, providing a unique dataset to better understand the relationship between tremor activities and large earthquakes. We computed envelope functions from the 2-8 Hz band-passed-filter data recorded by short-period and broadband stations. We used standard envelope cross-correlation technique to auto-detect and locate tremor and visually confirm the results as bursts of high-frequency, non-impulsive seismic energy that are coherent among many nearby stations. The preliminary tremor locations are scattered around the region where triggered tremors are located. In addition, we examined triggered tremors during the surface waves of the Chile earthquake. Although the dynamic stress from the Chilean event is higher than the tremor-triggering threshold of ~9 kPa in Taiwan, this event did not trigger tremor. However, we do find a moderate increase of tremor activity ~1 day after the Chile mainshock, and long after the Jiasian earthquake. In our next steps, we will refine our tremor detection and locations, and then quantify the relationship among the tremor, the Jiasian main shock, and distant earthquake.

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Last Modified: 2011 Aug 10

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