HR: 0830h
AN: V21D-0553    [PDF]
TI: En echelon knolls in the Nosappu Fracture Zone, NW Pacific: A possible leaky transform fault zone
AU: * Ogawa, Y
EM: yogawa@arsia.geo.tsukuba.ac.jp
AF: Prof. Yujiro Ogawa, Institute of Geoscience, University of Tsukuba, Tsukuba, Iba 305-8571 Japan
AU: Hirano, N
EM: nhirano@geo.titech.ac.jp
AF: Dr. Naoto Hirano, Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama, Tokyo, Tok 152-8551 Japan
AU: Shipboard Scientific Party KR03-07, .
EM: yogawa@arsia.geo.tsukuba.ac.jp
AF: Prof. Yujiro Ogawa, Institute of Geoscience, University of Tsukuba, Tsukuba, Iba 305-8571 Japan
AB: During JAMSTEC R/V KAIREI cruise KR03-07, we mapped significant en echelon arrays of knolls and ridges on the NNW-trending Nosappu Fracture Zone between Hokkaido and Shatsky Rise, NW Pacific. This fracture zone has been known to be irregular, including a deep-sea channel, the Nakwe Channel, enigmatic for inside the wide oceanic plate. Considering the previously recognized magnetic lineament dislocation, the fracture zone has long (more than 150 km) left-lateral strike-slip component as a ridge-ridge transform fault zone between the Izanagi and Pacific plates during Early Cretaceous. Detail multi-narrowbeam mapping around 37 N latitude, 150 E longitude (covering 78 km x 137 km), indicated many small knolls and ridges that form en echelon arrangement. Some are boomerang, sock or E-letter in shape. The two dominant directions of ridges are recognized, one is parallel to the fracture zone and the other is in left-handed en echelon fashion. Besides these ridges, there are other types of ridges or conical knolls lower than 500 m in relief; one is a group of rather large knolls extending to NE, roughly perpendicular to the fracture zone direction, and the other is independent small knolls, summing up to five or six in number. Another expression of a depression zone was recognized with a moderate angle to the fracture zone in a crank fashion. This may correspond to the so-called _gNakwe Channel_h which has been wrongly mistaken. Such en echelon arrays are involved in a 50 km wide NNW-SSE zone, which is sharply demarcated by fault scarps. These characteristics in the fracture zone area and associated knolls suggest that this part of the Nosappu Fracture Zone might have developed in a fault interaction area which has a left-lateral component of leaky transform faulting close to the spreading ridge.
UR: http://www.press.first.tsukuba.ac.jp
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 3045 Seafloor morphology and bottom photography
DE: 8010 Fractures and faults
DE: 8150 Plate boundary--general (3040)
DE: 9355 Pacific Ocean
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting