ALBERT

Description: Attenuation relations are derived for central Japan (broadly spanning the Kanto, Tokai, and Chubu regions) using recordings of small earthquakes (2.0〈 or =M (sub JMA) 〈 or =4.0 [Japan Meteorological Agency magnitude]) and moderate- to large-magnitude earthquakes (3.0〈 or =M (sub JMA) 〈 or =7.2). 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 (sub 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 (sub max) or kappa . We test our ability to predict strong ground motion by using our attenuation and source-scaling relations derived from the small-magnitude recordings to stochastically simulate peak ground acceleration, peak ground velocity, and 5% damped response spectral ordinates over a range of magnitudes and distances. The residuals of this simulation are found to be largely independent of distance and magnitude. We compare our attenuation relations against other relations derived for Japan. The residuals of these relations are analyzed and compared against those obtained from the model found in this study. We find that, in this study, the prediction of strong ground motions is possible using small-magnitude data and that the validity of the prediction extends across all magnitudes available for comparison (2.0〈 or =M (sub JMA) 〈 or =7.8). On the other hand, by using an alternative published predictive relation for Japan, derived using large-magnitude events, peak ground acceleration is significantly overestimated for small-magnitude earthquakes.