Tira Tadapansawut, Yuji Yagi, Ryo Okuwaki , SHINJI YAMASHITA, Kousuke Shimizu 

A moment magnitude 6.2 crustal earthquake occurred in northern Thailand on 5 May 2014, and its aftershocks exhibit several lineaments with conjugate pattern, involving geometric complexity in a multi-segmented fault system of the Phayao fault zone. However, a relationship between those geometric complexities and the rupture evolution of the 2014 Thailand earthquake is still elusive, which is critical to understand complex nature of the earthquake physics and to assess the hazard. Here we elaborated the newly developed flexible finite-fault inversion method, used it to invert the globally observed teleseismic P waveforms, and estimated the spatiotemporal distribution of both the slip and the fault geometry. We found the complex rupture evolution consisting of two rupture episodes along a conjugated strike-slip fault system that comprises two distinct fault planes. The fault system derived from our finite-fault solution exhibits geometric complexities including bends, which may have caused the perturbation of the rupture propagation and the triggering of the distinct rupture episodes. Our source model of the 2014 Thailand earthquake shows that even in the case of smaller-scale earthquakes, the rupture evolution can be complex when the underlying fault geometry is multiplex.