Regional differences in attenuation modelling for Eastern China
This paper describes the development of seismological models for three sub-regions within Eastern China. An important feature of the modelling is that two main types of local data were used to determine parameters for input into the seismological model. Shear wave velocity data was used in Step One of the procedure for deriving the upper crustal factors which are part of the seismological model. Two further steps were involved in incorporating the historical Intensity (MMI) data into the modelling. In Step Two, the simulated peak ground velocity (PGV) values were converted to MMI values, and site factor was calculated by dividing the inferred PGV value by the respective simulated PGV value for each given (short distance) earthquake scenario. In Step Three, the quality (Q) factor of the seismological model for each sub-region was calibrated in accordance with the criterion that site factors inferred from records of long distance earthquakes in the database match with the median site factor obtained in Step Two for short distance earthquakes. Importantly, the Q values obtained by this calibration method were highly consistent with Coda Q values (obtained for each sub-region from a previous study by Jin and Aki based on analysing records of local earth tremors). The calibrated Q values in combination with the developed crustal factors and geometrical attenuation factor constitute the regional seismological model for Eastern China. The seismological model so developed takes into account intra-regional differences and has been used to simulate strong ground motions by the stochastic method for assessing the potential seismic hazards in the region.