Shear-wave velocity model of the Chukuo fault zone,Southwest Taiwan,from cross correlation of seismic ambient noise |
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| Institution: | 1. Institute of Seismology, National Chung Cheng University, 168 University Road, Min-Hsiung, Chia-Yi 62102, Taiwan;2. National Center for Research on Earthquake Engineering, 200, Sec. 3, HsinHai Rd., Taipei 10668, Taiwan;1. Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;2. School of Earth Sciences, The University of Queensland, Brisbane, QLD 4072, Australia;3. Institute of Seismology, China Earthquake Administration, Wuhan 430000, China;4. PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China;5. Exploration and Development Corporation, PetroChina, Guangzhou 510000, China;1. Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan;2. Department of Medical Laboratory Science and Biotechnology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan;3. National Centre for Compositional Characterisation of Materials (CCCM), Hyderabad, India;1. CONICET – IANIGLA- CCT Mendoza – Argentina. Av. Dr. Ruiz Leal s/n, Parque General San Martín, 5500, Mendoza, Argentina;2. Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo. Mendoza, Argentina. A. Brown s/n. Chacras de Coria, Luján, CPA M5528AHB, Mendoza, Argentina;3. Departamento de Geología, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile;4. Instituto de Ciencias de la Ingeniería, Universidad de O´Higgins, Libertador Bernardo O´Higgins, 611, Rancagua, Chile |
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| Abstract: | The Chia-Nan (Chiayi-Tainan) area is in the southwestern Taiwan, and is located at the active deformation front of the collision of the Eurasian continental plate and the Philippine Sea plate, which causes complex folds as well as thrust fault systems in the area. The Chukuo fault zone is a boundary between the Western Foothill and the Western Coastal Plain in the Chia-Nan area. The nature of the crustal structure beneath the fault zone, especially the eastern part of the fault zone with mountain topography, has not been well known in detailed due to lack of drilling data as well as its limitation in using other geophysical methods, such as active source survey. In this study, we deployed an array with 11 broadband seismic stations to monitor the seismicity of the Chukuo fault zone. The array has recorded more than 1000 microearthquakes around this area. It provides an opportunity to use P- and S-wave travel time data to investigate the both the crustal P- and S-velocity in the fault zone, however due to the nature of the earthquake distribution, the ray density is relatively low at depth between 0 and 7 km. In addition, the uncertainty of S-wave reading for small earthquake also a limit in building precise S-velocity profile, Thus, we take the advantages of using cross-correlation of seismic ambient noise to investigate crustal S-velocity profile in the Chukuo fault area, especially in the mountain area where crustal faulting is a dominated phenomenon. The results indicate that S-wave velocity in the uppermost crust in the Chukuo fault zone is shown to be slower than previous studies. A low velocity layer exists at depth between 1 and 2 km in the east of the Chukuo Fault. The low S-velocity is related to a highly fractured upper crust due to intensive deformation caused by the orogenic process. |
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| Keywords: | Seismic ambient noise Green’s function Rayleigh wave Shear-wave velocity structure Chukuo fault |
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