Seismic Wave Attenuation Characteristics from the Ground Motion Spectral Analysis around the Kanto Basin

Abstract

In order to study the seismic wave attenuation characteristics of complex plate tectonics in and around the Kanto Basin, based on the focal mechanism and Slab1.0 model, the research area is divided into four regions. The one-step non-parametric generalized inversion technique was used to analyze the seismic wave attenuation characteristics of each region separately. The results show that the seismic path attenuation of earthquakes occurring in the shallow crust (Reg.1) is weak, and the seismic wave refraction at the crust–mantle boundary leads to almost no attenuation over a long hypocentral distance (>60 km), the frequency–dependent inelastic attenuation is also weak with the 0.5–20 Hz quality factor Q = 92.33f1.87. The seismic path attenuation of the upper mantle earthquakes occurring in the Kanto Basin (Reg.2) is strong, and the attenuation curve decreases with the increase of hypocentral distance, which is approximately parallel to the geometric diffusion R−2.0, the frequency–dependent inelastic attenuation is stronger with the quality factor Q = 27.75f1.08. The seismic path attenuation of subduction zone earthquakes (Reg.3 and Reg.4) is more obvious in the high–frequency band and has a frequency correlation, indicating that the attenuation of subduction zone earthquakes includes more inelastic attenuation. The frequency–dependent inelastic attenuation Q of Reg.3 and Reg.4 are 52.58f0.95 and 58.07f0.89, respectively.

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“…Ground motion is essential in hazard estimation because it may affect the seismic capacity. The observed ground motion can result from convolution between source, path effect attenuation, and site effect [23]. Knowing in detail information about attenuation structure makes it possible to estimate more reliable groud motion due to an earthquake.…”