Regional differences in attenuation modelling for Eastern China

Abstract

a b s t r a c tThis 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.

Use of Macroseismic Intensity Data to Validate a Regionally Adjustable Ground Motion Prediction Model

“…For SEA region, the proposed SWV profile resulted in a V S30 value that is the same as previous study (0.76 km/s) [68]. However, for SEC region, the SWV profile obtained from this study (V S30 = 1.45 km/s) is different from that presented by Tsang et al [16] (V S30 = 1.1 km/s, which is different from V S0.03 ). More local data for accurate SWV profile modelling is required in future studies.…”

“…However, very useful macroseismic intensity information expressed in terms of the modified Mercalli intensity (MMI) has been recorded on isoseismal maps for earthquakes that occurred in this region for over hundreds of years. This type of data has been used in investigations for studying the attenuation behaviour of earthquake ground motions in Australia [15,16] and in many other regions of low-to-moderate seismicity [17]. The analysis of MMI data can result in the development of a GMPE that can be representative of the strong motion transmission properties of earthquake-affected areas based on observations over a long-time span (without requiring recording instruments to be placed close to the epicentre of any earthquake).…”

“…Uncertainties with the modification factor for conversion from MMI on a soil site to MMI on a rock site: a factor of 1.5 was adopted for both SEA (recommended by AS1170. 4-2007 [64]) and SEC region (recommended by Tsang et al [16]). CAM can only give predictions on rock sites and thus the conversion between soil sites and rock sites is essential.…”

A Generic Shear Wave Velocity Profiling Model for Use in Ground Motion Simulation

“…More explicitly speaking, the reason is that the upper-crustal factor within a tectonic region can change dramatically for different locations, especially for the regions with various geological conditions. For example, various geological upper-crustal conditions have been reported within the SEC region by [19]. The upper-crustal conditions within SEC are not identical, and the shear-wave velocity (SWV or V S ) profiles for the three studied sub-regions ("SKP region", "YZP region", and "SCF region") are very different.…”

Signal processing in attenuation measurement with laser ultrasonics

“…Many researches showed in geophysics for the obvious viscoelastic property of the earth [1,2 ]. C. W. Horton [3] studied the particle motion of the earth surface, Anderson [4] et al analyzed viscoelastic characteristics from the perspective of waves.…”