A Magnetotelluric Transect Across the Mariana Subduction System
|A map of the Mariana subduction system showing the locations of seafloor MT instruments
Rob. L. Evans, A.D. Chave
Woods Hole Oceanographic Institution
N. Seama, T. Matsuno, H. Iwamoto, R. Tsujino
K. Baba, Y. Baba, H. Utada, A. Yoneda
Earthquake Research Institute, University of Tokyo
T. Goto, K. Suyehiro
G. Boren, G. Heinson, A. White
University of Adelaide.
A Japanese, US, and Australian collaborative research team carried out a marine magnetotelluric (MT) experiment across the central Mariana subduction-arc-back arc system, extending from the Pacific Ocean to the West Mariana Ridge through the Marina Trough. The purpose of the project was to provide a comprehensive
image of the electrical conductivity structure for the central Mariana subduction system.
Deployments of 33 ocean bottom electro-magnetometers (OBEMs), 7 ocean bottom electrometers (OBEs), and 7 ocean bottom magnetometers (OBMs) were made at 40 sites across the central Mariana subduction system. Observations
of naturally occurring geomagnetic and electric fields were made from December 2005 to September 2006. The length of the observation line is about 700km. East of the Trench, site spacing was approximately 40 km, but to the west the spacing was closer, particularly in the vicinity of the back-arc spreading center, where the sites were only a few kilometers apart.
We successfully recovered 28 OBEMs, 7 OBMs, and 6 OBEs at 35 sites. We also use data from a previous study, which adds another
8 sites to the observation line.