| dc.description.abstract | The 20 September 1999 Chi-Chi, Taiwan, Earthquake (Mw 7.6) was the largest earthquake to strike Taiwan in the twentieth century. At the mean time, long-period surface waves were excited in the western coastal plain of central Taiwan. The seismic signals were well recorded by the Central Weather Bureau’s strong motion seismometers. The surface wave period was between 2 and 10 seconds. Although there was no report on direct damage caused by surface waves, the breakage of several syrup tanks, at Taichung harbor, is suspected to be the result of surface waves. The long period surface wave is a potential source of damage to long period bridges and elevated railroad systems, such as high-speed bullet trains. In this study, we focus on simulating the factors that control the generation of long period surface waves in the western plain of central Taiwan. The numerical method used is the pseudo-spectral method. We tested several parameters to see the effects on generating surface wave signals. The tested parameters are the rupture velocity, fault dip angle, and whether the fault rupture arrives at the ground surface or not. In this study, we reach three conclusions. First of all, if a medium-sized earthquake occurs in the foothills of central Taiwan, long-period surface waves can be generated in the western coastal plain only if the fault rupture has reached the top low velocity sediments or the ground surface. Second, rupture velocity will strongly control the duration of surface waves. A slower rupture velocity will generate longer surface waves. Third, the excitation of surface waves is mostly controlled by the near surface fault rupture; the deeper part of the rupture will only affect body wave signals. | en_US |