Dynamic triggering of shallow earthquakes near Beijing, China

S U M M A R Y We perform a comprehensive analysis of dynamic triggering around the Babaoshan and Huangzhuang-Gaoliying faults near Beijing, China. The triggered earthquakes are identified as impulsive seismic arrivals with clearP and S waves in 5 Hz high-pass-filtered three-component velocity seismograms during the passage of large amplitude body and surface waves of large teleseismic earthquakes. We find that this region was repeatedly triggered by four earthquakes in East Asia, including the 2001 Mw 7.8 Kunlun, 2003 Mw 8.3 Tokachi-oki, 2004 Mw 9.2 Sumatra and 2008 Mw 7.9 Wenchuan earthquakes. In most instances, the microearthquakes coincide with the first few cycles of the Love waves, and more are triggered during the largeamplitude Rayleigh waves. Such an instantaneous triggering by both the Love and Rayleigh waves is similar to recent observations of remotely triggered ‘non-volcanic’ tremor along major plate-boundary faults, and can be explained by a simple Coulomb failure criterion. We are able to locate five of the earthquakes triggered by the Kunlun and Tokachi-oki earthquakes. These events occurred at shallow depth (<5 km) above the background seismicity near the boundary between NW-striking Babaoshan and Huangzhuang-Gaoliying faults and the Fangshan Pluton. We suggest that these triggered earthquakes occur near the transition between the velocity strengthening and weakening zones in the top few kilometres of the crust, and are likely driven by relatively large dynamic stresses on the order of few tens of KPa.