Imaging active faulting in the western Taiwan Strait.

Area of Science:

• Geophysics
• Tectonics
• Seismology

Background:

• Historical earthquakes in Fujian Province suggest significant tectonic activity in the western Taiwan Strait.
• The shallow crustal structure and active faulting in this region have been understudied.

Purpose of the Study:

• To investigate the shallow crustal structure of the western Taiwan Strait using new seismic data.
• To identify and characterize the Benhai fault and its kinematic behavior.
• To assess the activity and tectonic implications of faulting in the region.

Main Methods:

• Acquisition and analysis of reflection seismic data.
• Mapping of the Benhai fault's location and upper crustal geometry.
• Integration of seismicity and earthquake focal mechanism data.

Main Results:

• The Benhai fault has been mapped for the first time, with evidence of widespread faulting reaching the seafloor.
• Fault structures, including flower structures and terraced sidewall fault zones, indicate early-stage dextral strike-slip system development.
• Seismicity and focal mechanisms support the interpretation of an active dextral strike-slip fault system.

Conclusions:

• The Benhai fault is confirmed as an active structure in the western Taiwan Strait.
• The fault zone represents an early developmental stage of a dextral strike-slip system.
• This study highlights the significant, previously underappreciated, tectonic activity in the region.