Observation And Preliminary Discussion On Remotely Dynamic Triggering Earthquake In Beijing

Dynamic stresses carried by seismic waves (mainly by surface waves) from largeearthquakes can trigger earthquakes at a distant region. The1992Landers Mw7.3earthquake triggered remarkably widespread increase of seismicity in the western UnitedStates. Since then, remote dynamic triggering becomes one of the hottest research topics ofearthquake seismology. Previous studies suggested that dynamic triggering could occuralong major plate boundary regions and active geothermal or volcanic regions. However,some recent studies show that teleseismic earthquakes could also trigger seismic activity inrelatively stable continental regions. Previous studies have shown that dynamic triggering isrepeatedly observed in the NKY region of Beijing, but it is still unclear why remoteearthquakes could induce earthquakes in regions with relatively low background seismicity.Current models for dynamic triggering fall under two groups: one suggesting dynamicstresses from the mainshock change the state of a fault or the friction across a fault surface,and the other appealing to either hydrous or magmatic activation of crustal fluids, leading totriggered earthquakes. None of the models appears capable of accounting for the wordwidevariation of observations. Researchers have yet to make a great progress into understandingearthquake interaction, unless we could obtain more evidence by simulating the triggeredresponse to large earthquakes in terms of both lab experiments and computer modeling.Based on standard waveform processing and β statistical analysis, using seismic datacollected by the Beijing metropolitan Digital Seismic Network (BDTSN) and our temporaryseismic stations, we conducted a systematic search of dynamic triggering in Beijingfollowing the2010/02/27Mw8.8Chile earthquake. We found at least5triggeredmicroearthquakes during the direct surface waves of the Chile mainshock. However, we didnot find any evidence of triggered activity during multiple surface waves of the Chilemainshock that arrived later, and during the teleseismic waves of the Mw7.0Ryukyuearthquake occurred10hours earlier.We relocated all the triggered microearthquakes from2001to2012using the Hypoinverse-2000code. The relocation results show all the triggering microearthquakesoccurred near the Fangshan Pluton, mostly in the western subsolidus deformation zone. Thedynamic stresses calculated from those teleseismic earthquakes are in the range of7-130KPa.Comparing with the background seismicity of the NKY region given by regional seismicnetwork from2001to2012, our analysis indicates that the way of stress loading in the NKYregion plays a key role in remote triggering. In addition, the tectonic settings of the FangshanPluton, the favorable incident angle of the teleseismic surface waves could also contribute tothe dynamic triggering process.