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| Autor: | Chun-Yu Chiang, 姜竣友 |
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| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 Pingtung plain in the south of Taiwan is covered with hundreds of meters thick of soft sedimentary strata. These unconsolidated alluvial sand and gravel are mainly from the Central Range and Yushan Range. Chiang (1971) indicated that the plain sediments thick gradually from east to west according to the data from seismic surveys, deep boreholes, and surface geology. In this study, the slope of strata in the Pingtung Plain is neglected to simplify the calculation of horizontal-to-vertical spectral ratio (HVSR). Seismic wave will be amplified after propagating through these strata and leads to serious disaster. For Taiwan, a country located on an active plate boundary, it’s essential to clarify the site effect there. To know the site response, correct and detailed shallow velocity structure is necessary. Although there are several studies provided some velocity structures, their scales are all too large to provide enough information. In this study, HVSR of 308 sites were simulated to inverse the shallow velocity structure of Pingtung Plain in detail. In our simulation, the Haskell method had been used to calculate the theoretical HVSR of corresponding S wave velocity structure. To define the searching boundary and initial model, we refer to several previous studies. The S wave velocity profile, measured by Suspension P-S Logging Technique, from Engineering Geological Database for TSMIP. Chen (2016), Chiang (2011) used microtremor array to derived the shallow velocity structure. Lin et al. (2017) used receiver function to inverse the velocity structure of the TSMIP seismometer sites. A model with seven to nine layers covering a half space was set up for the Genetic Algorithm search (GA search). There are two unknown parameters for each layer, i.e., S-wave velocity and thickness. In order to reach the best solution, there are totally 1,250,000 repetitions for one site forward modeling. Finally, the best fitness velocity model will be picked selected and saved. By simulating the 308 HVSRs, we constructed the Pingtung plain near surface shear-wave velocity structure which useful for strong ground motion simulation and prediction in the future. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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