Bismarck 소판 경계부에서의 반사법 탐사와 PACMANUS에서의 deeptow 자력탐사

Abstract

The North and South Bismarck microplates lie on a complex tectonic region at the convergence of the Australian and Pacific Plates. These microplates show active tectonic movement so that many active and dormant volcanoes exist and earthquakes are frequent. On these plates many hydrothermal plumes have been discovered and many surveys for locating new plumes have been conducted. In the western Bismarck sea, one of the major structural feature is the seismic lineation which is considered as a boundary between the North and South Bismarck microplates, but the nature of this boundary has been poorly known.In 2003, Korea Ocean Research & Development Institute (KORDI) and CSIRO conducted geological and geophysical surveys in the western Bismarck Sea onboard R/V Onnuri. A multichannel seismic survey was adopted to study the crustal structures in the western Bismarck Sea. Seismic system comprises a 2.46-l sleeve gun, a 12-channel streamer with a group interval of 6.25m, and StrataVisor NX seismic recorder. Seismic data were processed using Seismic Unix and GEOVECTEUR. Seismic lines were designed to cross the inferred plate boundaries between the North and South Bismarck microplates. In the southern part of the survey area a fault zone with strike slip faults exists. This fault zone determines plate boundary between the North and South Bismarck microplates. On the section sediment thickness of seamounts is very thin. This implies that the age of their eruption is very young and there is a strong possibility of the existence of hydrothermal vent.Deeptow magnetic survey has been conducted over the PACMANUS hydrothermal vent field. Magnetometer was flown over the four drill sites of ODP Leg 193 at approximately 100-150 m above the sea floor. The deeptow magnetic data show how much better on resolution can be obtained by using such device.