2006 Volume 59 Issue 6 Pages 585-594
Natural magnetic field is attenuated by electrically conductive water. Therefore, the marine magnetotelluric survey has been used at long period range(1000 to 100000 sec), and investigated deep mantle structure. To obtain the crustal structure, however, electromagnetic data at the periods between 1 and 1000s is very important, for example the investigation for mega-thrust earthquake zone. Because there is no suitable ocean bottom electro-magnetometer (OBEM), we developed small sized OBEM and OBE system. On the other hand, controlled-source survey techniques are needed to obtain a shallower detail structure than conventional MT method. The DC resistivity survey is powerful tool for a shallower survey. Our marine DC resistivity sounding system has a 150m long electrode cable, and this cable attached the Deep-tow system. In this article, we describe the mechanism of developed OBE(M) and DC resistivity survey system, and show some results of field tests
