A Comparative Study on Attenuation and Source-Scaling Relations in the Kanto, Tokai, and Chubu Regions of Japan, Using Data from Hi-Net and KiK-Net

摘要

Attenuation relations are derived for central Japan (broadly spanning the Kant, Tokai, and Chubu regions) using recordings of small earthquakes (2.0M_JMA4.0 [Japan Meterological Agency magnitude]) and moderate- to large-magnitude earthquakes (3.0M_JMA7.2). We independently analyze data from both small-magnitude and moderate- to large-magnitude earthquakes to provide an insight into the use of attenuation relations derived in regions of low seismic activity. A strong correlation is found between the attenuation parameters derived from each dataset. We find that Q is strongly depth dependent and that apparent geometrical decay increases with increasing hypocentral distance. This is modeled by using a three segment decay function, with the initial decay forced to 1/R. Moment magnitudes are close to the published M_JMA magnitude, but are, on average, slightly higher. An increase in stress drop with magnitude is required in order to model both the small-magnitude and moderate- to large-magnitude datasets. Alternatively we show that a constant stress-drop model is suitable to model the response spectra of both small-magnitude and moderate- to large-magnitude earthquakes when considering the saturation of the source-corner frequency due to a static site filter such as f_max or .