08:30 〜 08:45
[S07-7-01] Shallow shear wave velocity model of Taiwan constructed from Receiver Function Analysis of strong motion stations
The high seismicity and major tectonic features of Taiwan are resulted from the active collisions. The young and fast orogeny in the island also forms a wide range of alluvium plains and basins that are filled with unconsolidated Quaternary sediment covering the bedrock. The obvious seismic site effect amplifies and extends incident seismic waves and can result in earthquake disasters. Therefore, a shallow velocity model, reflecting the real and complex seismic site effects in these areas, is necessary for ground motion simulation and prediction in Taiwan.
The advantage of the even strong motion stations and numerous records in Taiwan has been taken to apply the Receiver Function (RF) technique to high-frequency acceleration seismograms recorded by Taiwan Strong Motion Instrumentation Program (TSMIP) stations to estimate the shallow shear wave velocity (Vs) structures. In the RF analyses of this study, an average RF of each station was calculated to enhance the converted phases and reduces the inharmonic arrivals. Based on the geological, geophysical, and Engineering Geology Database for TSMIP (EGDT) drilling data, an initial layer model with variable Vs and thickness was assumed to model RF and estimate Vs profile of a station by Genetic Algorithm (GA) search. Finally, the one-dimensional shallow Vs profiles of over 700 stations were estimated by RF analysis and forward modeling with GA search. All the results proved that this method is not only effective in teleseismic but also strong motion records to construct a shallow Vs structure of alluvium plain (or basin) overlaying a hard bedrock. Based on the Vs structures estimated in this study, a shallow velocity model of Taiwan was preliminarily constructed for applications of seismology and earthquake engineering. In addition, the results were also compared with the Vs30 of EGDT to confirm the site conditions of TSMIP stations and provide important site parameters such as engineering bedrock and Z1.0.
The advantage of the even strong motion stations and numerous records in Taiwan has been taken to apply the Receiver Function (RF) technique to high-frequency acceleration seismograms recorded by Taiwan Strong Motion Instrumentation Program (TSMIP) stations to estimate the shallow shear wave velocity (Vs) structures. In the RF analyses of this study, an average RF of each station was calculated to enhance the converted phases and reduces the inharmonic arrivals. Based on the geological, geophysical, and Engineering Geology Database for TSMIP (EGDT) drilling data, an initial layer model with variable Vs and thickness was assumed to model RF and estimate Vs profile of a station by Genetic Algorithm (GA) search. Finally, the one-dimensional shallow Vs profiles of over 700 stations were estimated by RF analysis and forward modeling with GA search. All the results proved that this method is not only effective in teleseismic but also strong motion records to construct a shallow Vs structure of alluvium plain (or basin) overlaying a hard bedrock. Based on the Vs structures estimated in this study, a shallow velocity model of Taiwan was preliminarily constructed for applications of seismology and earthquake engineering. In addition, the results were also compared with the Vs30 of EGDT to confirm the site conditions of TSMIP stations and provide important site parameters such as engineering bedrock and Z1.0.