Submarine landslide hazard off Northeastern Taiwan

Abstract:

In the northern margin of the western end of the Okinawa Trough, three major submarine channels running across the continental margin are distinctive. From east to west, they are the North Mein-Hua Submarine Canyon, Mein-Hua Submarine Canyon and the Keelung Valley. To the east of the Mein-Hua Submarine Canyon, the slope of the continental margin is quite gentle, implying that the risk of slope instability is low. However, between the Keelung Valley and the Mei-Hua Submarine Canyon, the slope is rather steep. We have conducted multi-channel reflection seismics, sub-bottom profilers and multi-beam bathymetry in this area. The results show two general trends of fracture or faulting. The NE-SW trending faults generally follow the major orientation of the Taiwan mountain belt. Thus, these faults could be reverse faults from the former collisional thrust faults to currently post-collisional normal faults. Another almost E-W trending faults are consistent with the N-S extending of the Southern Okinawa Trough. Because the most significant faulting in the northwest end of the study is probably associated with the offshore extension of the Kenchiao Fault or the Sanchiao Fault, we consider either of these two faults as the northeast boundary (headwall) of the potential submarine landslide. Taking the stability slope angle of 0.5 degree as the stable landslide slope as shown in the area to the northeast of the study area, we estimate the total volume of the potential submarine landslide could be 300 cubic kilometers. Such a landslide volume may generate a local tsunami and affect especially the northeast coast of Taiwan.