Presenter: Chi-Lo Huang
Date: 2016/03/17
Abstract
The westernmost Okinawa Trough back-arc basin is located behind the Ryukyu islands and earthquakes and volcanism are widely distributed. In the northern margin of the western end of the Okinawa Trough, there are three obviously submarine channels with orientation of NW-SE across the continental margin. From east to west, they are the North Mein-Hua Submarine Canyon, Mein-Hua Submarine Canyon and the Keelung Valley.
To better understand the extensional tectonics and the potential submarine landslides. In the northern margin of the western end of the Okinawa Trough, we have conducted multi-channel reflection seismics, sub-bottom profilers and multi-beam bathymetry in the study area.
Our results show the general trends of faulting. The NE-SW trending faults generally follow the major trend of the Taiwan mountain belt. Those faults could be reverse faults from the inherited collisional thrust faults to currently post-collisional normal faults. Using fish-finder echo sounder, we have found many plumes along some continental slopes. Except for the plumes near the submarine volcanos, the plumes can be separated into two groups by east longitude 122° 15’E. The plumes in the east are stronger than the west. The east group is associated with the present back-arc spreading system (0.1~Ma). West of 122° 15'E, the features reveal the direction of extension is N150° (2~0.1Ma). Near Guishan Island, several faults trend N60° have been observed. We suggest that it could be related to the linear structure located on the Keelung Shelf. With the seismic profiles, we couldn’t see the clear failure surface. We consider the movement of the submarine landslides in the Keelung Shelf off northeastern Taiwan could be in a spread type.
Reference
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李易隆，「台灣東北部海域海底火山與熱液噴泉之研究」，國立海洋大學，碩士論文，民國94年。