Three - Dimensional Magnetotelluric Inversion Using Generalized RRI Method

Kazunobu Yamane 1), Shinji Takasugi 1), Hee Joon Kim 2), and Ki Ha Lee 3)

1) Geothermal Energy Research and Development Co., Ltd., Tokyo, Japan. e-mail: yamane@gerd.co.jp
2) Pkyung National University, Pusan, S. Korea.
3) Lawrence Berkeley National Laboratory, University of California, CA, USA.

Abstract

Recently, 3-D MT inversion has been reported in order to investigate geological targets in 3-D environments(Madden and Mackie, 1989; Mackie and Madden, 1993; Spichak et al., 1995; to list a few). Most of these studies, however, require enormous computational time and memory to evaluate EM couplings between all elements for the sensitivity matrix. An innovative inversion using the straightforward Born or the quasi-linear (Zhdanov and Fang, 1996) method is much desired. These approximate methods, however, although computationally efficient, have shown limited applications in investigating a simple earth models. One of the promising approaches may be the rapid relaxation inversion (RRI) reported by Smith and Booker (1991). In this method the actual inversion is carried out for each column in 1- D fashion. The forward modeling used may be rigorous, so that as iteration is continued one hopes to have the lateral effects gradually accounted for. Recently, the method has been generalized (GRRI) by adding lateral effects explicitly, so that models of fairly rapid lateral variation in conductivity can be treated (Lee et al., 1995; Yamane et al., 1996). We have been working on extending the GRRI approach to 3-D with encouraging results using synthetic models. The GRRI approach will be applied to the Minami-Kayabe data set and preliminary findings will be presented.

raeg98@tansa.kumst.kyoto-u.ac.jp

Last modified: Mon Sep 21 09:24:29 1998