Remotely Triggered Earthquakes in South-Central Tibet Following the 2004Mw 9.1 Sumatra and 2005Mw 8.6 Nias Earthquakes

yao, dongdong ; peng, zhigang ; meng, xiaofeng;

We conduct a systematic search for remotely triggered earthquakes in South-Central Tibet following the 2004 December 26Mw 9.1 Sumatra and 2005 March 28Mw 8.6 Nias earthquakes. We apply a Network Waveform Matched Filter Technique (NWMFT) to continuous seismic
data recorded by the Hi-CLIMB array to obtain more complete earthquake catalogues in this region. Local earthquakes with magnitudes up to 4 were triggered during the large-amplitude
surface waves, and most of them occurred in Gaize immediately north of the Bangong-Nujiang Suture Zone separating the Lhasa and Qiangtang Terranes. The triggered seismicity lasted 50 hr following the Sumatra and a few hours following the Nias main shocks, respectively.
The difference in triggering durations could be explained by the fact that the Sumatra main shock excited long-duration surface waves with cumulative energy density 15 times more than that of the Nias main shock. In both cases, the transient increase in seismicity is followed by
a moderate transient decrease, likely reflecting a ‘dynamic shadow effect’, where there is a temporary lack of seismic events following the remotely triggered seismicity. In comparison, we do not find any clear evidence of dynamic triggering (with a magnitude of completeness
Mc = 1.7) in the Zhongba region, where a Mw 6.3 normal faulting earthquake occurred 10 d after the 2005 Nias event.