Rupture Complexity of the 1970 Tonghai and 1973 Luhuo Earthquakes , China , from P - Wave Inversion , and Relationship to Surface Faulting

The source processes of the 4 January 1970, Tonghai earthquake (Ms = 7.5) and the 6 February 1973, Luhuo earthquake (Ms = 7.5) in southwestern China were investigated using an inversion technique on the very complex body waves. The two earthquakes were associated with 48 and 90 km of surficial strike-slip rupture, respectively, and the distribution of displacement with distance along the fault was well documented by field studies of both events. The source process for both earthquakes comprised three to four subevents with different moments and rupture durations. These calculated parameters agree well with the field observations and aftershock distributions, particularly in the total rupture length and in the amount and asymmetry of fault displacements relative to the locations of the main epicenters.