摘要：The cause of asperities (i.e., high-slip regions) remains the subject of much debate in seismology.Several tomography studies have reported previously that high-velocity bodies coincide with asperities.However, it remains unclear whether the heterogeneity of the crust generates these asperities.This can be addressed by conducting stress analysis.The 2004 Chuetsu, Japan earthquake is one of the best examples, since a detailed 3D seismic velocity structure was elucidated.For the resulting structural model, we calculated the heterogeneous stress distribution numerically, adding tectonic loading.Then, we calculated the distribution of the stress drop on the fault based on a frictional coefficient μ d, the pore fluid factor λ v, and the tectonic loading ratio c .We assumed λ v to be 0.85 based on a previous study and calculated the corresponding slip distributions and seismic moment.To have been responsible for this Mw6.6 earthquake, the parameters μ d and c must have been located somewhere along a particular line in c - μ d space; this constrains the possible range of these parameters.We found that the asperity region for the above slip distribution corresponds approximately to that of the kinematic model, which suggests that the asperity may have been created by heterogeneity in the crustal structure.
