Discussion on seismogenic fault of the Ludian M_s6.5 earthquake and its tectonic attribution

The Ludian 6.5 earthquake occurred in the marginal zone between the eastern Tibetan Plateau and the Yangtze Craton owing to southeastward motion of the Sichuan-Yunnan rhombic block.Although no surface rupture zone was observed during the emergency scientific investigation in the epicenter,the spatial linear distribution of the aftershocks recorded by a local seismic network,with the dominated axial azimuth of the earthquake intensities and earthquake ground fissures,displays that the seismogenic fault of the Ludian earthquake is a NW-trending left-lateral strike-slip fault,named as the Baogunao-Xiaohe fault,which may belong to the southern termination of the Daliangshan fault.Coulomb stress calculation shows that the occurrence of this earthquake uploads the adjacent active fault systems and the seismic risk for the historical seismic gaps could not be ignored.