Imaging active faulting in the western Taiwan Strait

Large, destructive historical earthquakes off the coast of China’s Fujian Province point to important tectonic activity in the western Taiwan Strait that, until recently, has received little attention. We present newly acquired reflection seismic data that is used to study the shallow crustal structure of the western Taiwan Strait. With these data we map the location of the Benhai fault for the first time, describe its upper crustal geometry and, in combination with seismicity and earthquake focal mechanisms, interpret its kinematics. These new data demonstrate that there is wide spread evidence of faulting that reaches the sea floor in the western Taiwan Strait, clearly indicating that the Benhai fault is active. Faults that cut up section from steep basin sidewalls to form flower structures or terraced sidewall fault zones, together with the fault and basin map pattern, are consistent with this fault zone being in the early developmental stages of a dextral strike-slip system. Earthquake focal mechanisms, although not definitive, support the model of an active dextral strike-slip fault system in the western Taiwan Strait. © 2020, The Author(s).ZYF acknowledge funding supported by the National Natural Science Foundation of China (Grant No. 41774104). KC acknowledge funding supported by the Ministry of Science and Technology (MOST 108-2116-M-008-022-MY3). JAM and DB acknowledge funding provided by the Spanish Ministerio de Economia y Competividad grant PGC2018-094227-B-I00. DB also acknowledges financing through the Salvador de Madariaga program (project PRX17/00036) provided by the Spanish Ministerio de Educación, Cultura, y Deporte for a 6 month stay at NCU. We also thank C.-W. Ho of Central Weather Bureau for providing the earthquake catalogue.Peer reviewe