[S07-P] Poster

[S07-P-23] The ground motion signature of supershear rupture in Burrdge-Andrews and free-surface-induced mechanisms

^○Jiankuan Xu, Xiaofei Chen (Southern University of Science and Technology, Shenzhen, China)

There are two main mechanisms of supershear transition. One is usually called `the Burridge-Andrews mechanism' (BAM), on which a daughter crack nucleates ahead of the main crack tip by a high enough stress combining the peak shear stress moving at the shear wave speed developing ahead of the main crack tip (Andrews, 1976). The other one occurs on the free surface causing by the phase conversion of SV-P at the free surface (Kaneko and Lapusta, 2010; Xu et al., 2015), which we call `the free-surface-induced supershear' (FSI). Compared the rupture scenarios in BAM and FSI as shown, an evident different phenomenon is observed. That is, only one secondary supershear rupture front is nucleated in the in-plane direction in BAM whereas the secondary supershear rupture front is nucleated at the free surface in FSI. Besides, if the level of shear stress is high enough, both tow supershear rupture fronts are nucleated. These differences will finally results varying ground motion characteristics and radiation frequency contents. We perform systematic studies about this ground motion signatures of tow supershear mechanism. It will offer a practical tool to identify the supershear mechanism from the observation conversely and even the tectonic stress state since which cause different supershear mechanisms.