Fault zone Q values derived from Taiwan Chelungpu Fault borehole seismometers (TCDPBHS)

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Title:	Fault zone Q values derived from Taiwan Chelungpu Fault borehole seismometers (TCDPBHS)
Authors:	林彥宇;Wang, Yu-Ju;Lin, Yen-Yu;Lee, Meng-Chieh;Ma, Kuo-Fong
Contributors:	地球科學學院地球科學學系
Keywords:	Boreholes;Chelungpu Fault;Fault-zone attenuation;Faults;Fracture mechanics;Q values;San Andreas Fault;Seismic attenuation;Seismic phenomena;Slip;Spectra;Taiwan Chelungpu Fault Drilling Project
Date:	2012-11-20
Issue Date:	2026-04-23 11:34:06 (UTC+8)
Publisher:	Elsevier;Elsevier B.V
Abstract:	摘要： The attenuation factor, Q, at a fault zone is an important parameter for understanding the physical properties. In this study, we investigated the Q value of the Chelungpu Fault, the main rupture of the Mw 7.6 Chi-Chi earthquake, using the 7-level TCDP borehole seismometer array (TCDPBHS). The TCDPBHS was deployed at depths from 945 to 1270m throughout the 1999 ruptured slip zone at 1111m. Three borehole seismometers (BHS1–BHS3) were placed in the hanging wall, and the remaining three (BHS5–BHS7) were placed in the foot wall, with BHS4 near the slip zone. The configuration allowed us to estimate the Q-structure of the recent ruptured fault zone. In this study, we estimated Q values between BHS1 and BHS4, Qs1 (Qp1) at the fault zone and between BHS4 to 2km in depth, Qs4 (Qp4) beneath the fault zone. We utilized two independent methods, the spectral ratio and spectral fitting analyses, for calculating the Q value of Qs1 (Qp1) in order to provide a reliability check. After analyzing 26 micro-events for Qs and 17 micro-events for Qp, we obtained consistent Q values from the two independent methods. The values of Qs1 and Qp1 were 21–22 and 27–35, respectively. The investigation for the value of Qs4 was close to 45, and Qp4 was 85. These Qp and Qs values are quiet consistent with observations obtained for the San Andreas Fault at the corresponding depth. A low Qs1 value for the recent Chelungpu Fault zone suggests that this fault zone has been highly fractured. Qs values within the Chelungpu Fault, similar to those within the San Andreas Fault, suggest that the Q structure within the fault zone is sedimentary rock independent. However, the possible existence of fluids, fractures, and cracks dominates the attenuation feature in the fault zone. ► We used the 7-level TCDP borehole seismometers array data to estimate the Qs and Qp value near the Chelungpu fault zone. ► We obtained consistent Q values from the two independent methods, spectral ratio and spectral fitting. ► The values of Qs and Qp were 21-22 and 27-35, respectively. ► Qs values within the Chelungpu Fault, similar to those within the San Andreas Fault. ► The result suggests that the Q structure within the fault zone is sedimentary rock independent. 出版者： Elsevier B.V 出版日期： 2012-11-20 出處： Tectonophysics, 2012-11, Vol.578, p.76-86 資源來源： Elsevier ScienceDirect Journals Complete 版權： 2011 Elsevier B.V. 識別號： ISSN: 0040-1951 識別號： EISSN: 1879-3266 識別號： DOI: 10.1016/j.tecto.2011.12.027
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