SEISMIC VELOCITY CHANGES ASSOCIATED WITH THE 2008 WENCHUAN EARTHQUAKE FROM REPEATING EARTHQUAKES

The 2008 Wenchuan Earthquake, which occurred along the Longmenshan Fault, is one of the most destructive natural disasters in human history. We monitored the temporal changes of seismic velocity using repeating earthquakes (i.e. waveform doublets) between 2008 and 2014 along the fault zone. We exhaustively search repeating earthquakes with magnitude at least 3.0 from the continuous records of several permanent stations near the fault, and then examine the quality of doublets using the records of all available other stations. We further use the technique of coda-wave interferometry between the high-quality doublets to monitor the seismic velocity changes along the fault zone. Post-seismic healing, indicated by velocity increase, is observed from mid 2008 to early 2011 beneath most stations near the fault. Later velocity changes from 2011 to 2014 are more subtle and nonuniform, with velocity fluctuating beneath most stations.