Modification of the network-MT method and its first application in imaging the deep conductivity structure beneath the Kii Peninsula, southwestern Japan

Satoru Yamaguchi, Makoto Uyeshima, Hideki Murakami, Sirou Sutoh, Daichi Tanigawa, Tsutomu Ogawa, Naoto Oshiman, Ryokei Yoshimura, Koki Aizawa, Ichiro Shiozaki, Takafumi Kasaya

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The Network-Magnetotelluric (NMT) method is well-suited for investigating deep and large-scale conductivity structure; however, application of the method is strongly dependent on the availability of telecommunication facilities (specifically, metallic transmission cables). To overcome the problem posed by the progressive replacement of metallic transmission cables with fiber cables, we developed a modified NMT (modified NMT) method consisting of purpose-built electrodes, making use of local metallic telecommunication lines, without a transmission cable. We first applied this modified NMT method over the Kii Peninsula, southwestern Japan, undertaking two-dimensional conductivity modeling along a transect across the central part of the peninsula. The model is characterized by a large (∼20 km wide and depths of 10-60 km) and highly conductive (<10 Ω m) zone in the central part of the peninsula between the Conrad discontinuity and the upper surface of the Philippine Sea slab. This zone contains the hypocenters of many deep low-frequency tremors but regular earthquakes are rare. The zone also corresponds to a high-Vp/V s area. The presence of fluid in the zone plays a key role in the absence of regular earthquakes, occurrence of deep low-frequency tremors, and elevated Vp/Vs values, as well as enhancing conductivity.

Original languageEnglish
Pages (from-to)957-971
Number of pages15
Journalearth, planets and space
Volume61
Issue number8
DOIs
Publication statusPublished - Jan 1 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geology
  • Space and Planetary Science

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