**3. Data acquisition and processing**

In this study, we used the multichannel reflection seismic data collected by the Taiwanese research vessel *Ocean Researcher II.* The source energy was shot via a 210-cubic inch GI gun with shot interval of 37.5 m. The reflection seismic data were acquired through a 24-channel, 150-meter long streamer, with a 1-ms sampling rate. The reflection seismic data were processed by the ProMAX and KINGDOM software at the Institute of Oceanography, National Taiwan University. The data-processing procedures include trace editing, geometry set-up, band-pass filtering, amplitude compensation, predictive deconvolution, velocity analysis, normal move-out correction, stacking, water velocity F-K time migration, and water column mute. Bathymetric dataset is a 500-m gridded data, produced by compiling shipboard and global dataset [32]. The bathymetric charts are prepared by the GMT [33].
