Abstract

A database of 1597 accelerograms from more than 500 events (3.3<Ms<8.0) of the 2008 Wenchuan and 2013 Lushan earthquakes, recorded on 44 stations in the range of 0–300 km, is used to study the characteristics of κ, which is the key parameter controlling the shape of Fourier acceleration spectrum at high frequency in stochastic simulation.

The results indicate that κ is independent of magnitude but clearly dependent on near‐surface geology, site condition, and epicenter distance. The obtained dependences of κ on distance in the Songpan–Garzê orogen (SGO) and western Sichuan basin (WSB) are 0.0001427 and 0.0001031  s/km, respectively. The average κ0 of the horizontal component (forumla) of the WSB and SGO ranges from 0.0144 to 0.0469 s and from 0.0321 to 0.0539 s, respectively. The dependence of forumla on site condition shows opposite tendencies in the WSB and SGO. In the SGO, it suggests that VS30 cannot fully represent the features of near‐surface geology, which is believed to be the main contributor of forumla. Furthermore, we observed that the spatial distributions of κ0 of the horizontal and vertical components are closely related to elevation and velocity images at 0–10 km depth, respectively. The correlations of forumla and elevation in the Longmen Shan, southeastern Alps and northern Dinarides region, and ANZA seismic network are studied. The results show good correlation and indicate that elevation may be used as a complementary parameter to develop a regional forumla model in addition to the forumla correlation.

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