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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L10307, doi:10.1029/2005GL022539, 2005

Detection of triggered deep low-frequency events from the 2003 Tokachi-oki earthquake

Masatoshi Miyazawa

Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan


Jim Mori

Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan


Abstract

We show the level of increased/decreased seismicity mapped across Japan immediately following the 2003 Tokachi-oki earthquake (Mw 8.1) of September 25, 2003 (UT) by use of the β-statistic. Significant dynamic triggering of events is found near the Nankai subduction zone 900–1400 km from the earthquake. The events are inferred to be dynamically triggered deep low-frequency earthquakes, of a type that often occur in this region. The triggering appears to be caused by the long-period oscillations of the surface waves, which may be effective in triggering fluid-related events. The region that showed the highest level of triggered events, was an area of elevated activity in the Bungo strait where a slow-slip event was in progress.

Received 25 January 2005; accepted 21 April 2005; published 21 May 2005.

Index Terms: 7209 Seismology: Earthquake dynamics (1242); 7215 Seismology: Earthquake source observations (1240); 7223 Seismology: Earthquake interaction, forecasting, and prediction (1217, 1242); 7230 Seismology: Seismicity and tectonics (1207, 1217, 1240, 1242); 7255 Seismology: Surface waves and free oscillations.

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Citation: Miyazawa, M., and J. Mori (2005), Detection of triggered deep low-frequency events from the 2003 Tokachi-oki earthquake, Geophys. Res. Lett., 32, L10307, doi:10.1029/2005GL022539.