Dynamics and Near‐Field Surface Motions of Transitioned Supershear Laboratory Earthquakes in Thrust Faults

Abstract We study how the asymmetric geometry of thrust faults affects dynamics supershear ruptures and their associated trailing Rayleigh as they interact with free surface, investigate resulting near‐field ground motions. Earthquakes are mimicked by propagating laboratory along a frictional interface 61° dip angle. Using an experimental technique that combines ultrahigh‐speed photography digital image correlation, we produce sequences full‐field evolving measurements particle displacements velocities. Our measurement capability allows us to confirm quantify asymmetry between motions hanging footwalls, larger velocity magnitudes occurring at wall. Interestingly, because motion wall is generally near‐vertical, while footwall direction shallower than angle fault, horizontal surface components found be The attenuation in distance from fault trace it more pronounced vertical component one. Measurements rotations experimentally interaction rupture can interpreted through torqueing mechanism leads reduction normal stress near for earthquakes. Nondimensional analysis shows consistent larger‐scale numerical simulations well field observations