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Fine Structure of the Chenghai Fault Zone, Yunnan, China, Constrained From Teleseismic Travel Time and Ambient Noise Tomography
Author(s) -
Yang Hongfeng,
Duan Yaohui,
Song Junhao,
Jiang Xiaohuan,
Tian Xiaofeng,
Yang Wei,
Wang Weitao,
Yang Jun
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2020jb019565
Subject(s) - seismology , geology , fault (geology) , noise (video) , ambient noise level , geodesy , seismic array , seismic tomography , anomaly (physics) , travel time , aperture (computer memory) , geophysics , sound (geography) , physics , acoustics , geomorphology , image (mathematics) , artificial intelligence , computer science , transport engineering , engineering , condensed matter physics , mantle (geology)
To derive high‐resolution fault zone (FZ) structure of the Chenghai fault in Yunnan, southwestern China, we deployed a linear dense array crossing the fault from January to February 2018. The array consisted of 158 short‐period (5 s) three‐component instruments and spanned an aperture of ~8 km with average station spacing of 40–50 m. During the 1‐month deployment, 20 teleseismic earthquakes with moment magnitudes larger than 5.5 and 41 local earthquakes were recorded. We first analyzed the travel times of P and S waves from teleseismic earthquakes to determine the boundaries of the FZ. After correcting the station‐event geometry effects, teleseismic travel time differences between the reference station, and all other stations clearly marked a zone of 3.4 km in width with distinct travel time anomaly, suggesting a low‐velocity zone (LVZ) surrounding the Chenghai fault. We then conducted ambient noise tomography and found that the S wave velocity of the LVZ was reduced by 60% and 40% compared to the northwest and southeast of the LVZ, respectively. Our ambient noise results suggested the LVZ extending to ~1.5 km in depth, consistent with the travel time anomalies of teleseismic earthquakes. Integrating ambient noise tomography with teleseismic travel times in a dense array with such an aperture is an effective approach for resolving FZ structure and depth extent.