THE RESEARCH ON FAULT PARAMETER AND SLIDING BEHAVIOR OF THE 1927 GULANG M8.0 EARTHQUAKE

The Gulang M8.0 great earthquake occurred in 1927,many places in Gulang and adjacent areas had suffered destruction in various degrees. So far,divergences exist in the former studies on its seismogenic structure. It is known that clustered small earthquakes often occur in vicinities of fault plane of large earthquake. In this study,the precisely relocated earthquakes which occurred near the earthquake rupture zone between 1985 and 2012 are used,and two strip-shaped zones of clustered small earthquakes are chosen according to the previous studies of the causative structure of this earthquake. Based on the simulated annealing and Gauss-Newtonian nonlinear inversion algorithms,we obtained fault plane parameters of the earthquake such as strike,dip,and location using data of densely concentrated small events. On this condition,rake angles of the fault plane are further inferred from regional tectonic stress parameter. Then we discussed briefly the seismogenic environment and causal mechanism of the earthquake,combined with the results of deep tectonics and surface investigations. The focal fault we inverted locates within the meizoseismal area( intensity Ⅺ)of the Gulang M8.0 in 1927,suggesting that the focal fault obtained by inversion is possibly the causative structure of this earthquake. Besides,we found a clustered zone of small earthquakes near the south-central part of the main fault,and a fault plane could be derived from them,which we think might be a tensional seismic fault developed on the main fault when the whole earthquake-hit region rotated counterclockwise during the big earthquake.