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Magnetotelluric investigations for the seismically active area in Northern Miyagi Prefecture, northeastern Japan

Abstract

The ELF- and the ULF-MT surveys were carried out in the northern part of Miyagi Prefecture, northeastern Japan. This area is one of the most seismically active areas in this region, where hypocenters of microearthquakes are distributed on a fault plane at depths from 2 to 16 km. The aim of the present study is to investigate the relationship between electrical resistivity structure and the hypocentral distribution of microearthquakes in the area. The calculated impedance tensor at each site has been obtained from the observed data and decomposed to remove galvanic distortion, provided that the regional strike is N32?E to obtain the 2-D apparent resistivity and phase responses. The resistivity structure obtained by the inversion process using smoothness constraint shows that the relatively electrically conductive layer at depths from 4 to 10 km corresponds to the zone where the microearthquakes occur. The fact that the conductive zone correlates with the hypocentral zone is probably attributed to fluids in the crust. Another more conductive block is found at depths from 1 to 3.5 km and the bottom boundary of this conductor appears to restrict the uppermost depth where the microearthquakes occur. This subsurface conductor is interpreted as a marine sediment deposited during the Tertiary period. In the lower crust, the relatively conductive blocks (lower than 5Ω m) exist below a depth of 15 km.

References

  • Bahr, K., Interpretation of the magnetotelluric impedance tensor: regional induction and local telluric distortion, J. Geophys., 62, 119–127, 1988.

    Google Scholar 

  • Bahr, K., Electrical anisotropy and conductivity distribution functions of fractal random networks and of the crust: the scale effect of connectivity, Geophys. J. Int., 130, 649–660, 1997.

    Article  Google Scholar 

  • Chave, A. D. and J. T. Smith, On electric and magnetic field galvanic distortion tensor decompositions, J. Geophys. Res., 99, 4669–4682, 1994.

    Article  Google Scholar 

  • Chave, A. D., D. J. Thomson, and M. E. Ander, On the robust estimation of power spectra, coherences, and transfer functions, J. Geophys. Res., 92, 633–648, 1987.

    Article  Google Scholar 

  • Frape, S. K. and P. Fritz, Water-rock interaction and chemistry of groundwaters from the Canadian Shield, Geochim. Cosmochim. Acta, 48, 1617–1627, 1984.

    Article  Google Scholar 

  • Gamble, T. D., W. M. Goubau, and J. Clarke, Magnetotellurics with a remote magnetic reference, Geophys., 44, 53–68, 1979.

    Article  Google Scholar 

  • Goto, T., Study on the electrical resistivity structure around the seismogenic zone in the Crust, Ph.D. Thesis, Kyoto Univ., 188 pp., 1997.

  • Goto, T., N. Oshiman, and N. Sumitomo, The resistivity structure around the hypocentral area of the Ebino Earthquake Swarm in Kyushu district, Japan, J. Geomag. Geoelectr., 49, 1279–1291, 1997.

    Article  Google Scholar 

  • Groom, R. W. and R. C. Bailey, Decomposition of magnetotelluric impedance tensors in the presence of local three-dimensional galvanic distortion, J. Geophys. Res., 94, 1913–1925, 1989.

    Article  Google Scholar 

  • Gupta, H. K., S. V. S. Sarma, T. Harinarayana, and G. Virupakshi, Fluids below the hypocentral region of Latur earthquake, India: Geophysical indicators, Geophys. Res. Lett., 23, 1569–1572, 1996.

    Article  Google Scholar 

  • Harinarayana, T., Combination of EM and DC measurements for upper crustal studies-A brief review, Proc. of 14th Workshop on Electromagnetic. Induction in the Earth, 193–214, 1998.

  • Hyndman, R. D., Dipping seismic reflectors, electrically conductive zones and trapped water in the crust over a subducting plate, J. Geophys. Res., 93, 13391–13405, 1988.

    Article  Google Scholar 

  • Jones, A. G., Static shift of magnetotelluric data and its removal in a sedimentary basin environment, Geophys., 53, 967–978, 1988.

    Article  Google Scholar 

  • Jones, A. G. and R. W. Groom, Strike-angle determination from the magnetotelluric impedance tensor in the presence of noise and local distortion: rotate at your peril!, Geophys. J. Int., 113, 524–534, 1993.

    Article  Google Scholar 

  • Jödicke, H., Water and graphite in the earth’s crust-an approach to interpretation of conductivity models, Surv. Geophys., 13, 381–407, 1992.

    Article  Google Scholar 

  • Kanda, W., H. Utada, M. Mishina, and N. Sumitomo, A deep transient EM experiment in the northern part of Miyagi Prefecture, northeastern Japan, J. Geomag. Geoelectr., 48, 1265–1280, 1996.

    Article  Google Scholar 

  • Kariya, K. A. and T. J. Shankland, Electrical conductivity of dry lower crustal rocks, Geophys., 48, 52–61, 1983.

    Article  Google Scholar 

  • Kono, T., K. Nida, S. Matsumoto, S. Horiuchi, T. Okada, K. Kaihara, A. Hasegawa, S. Hori, N. Umino, and M. Suzuki, Microearthquake activity in the focal area of the 1962 northern Miyagi Prefecture (M 6.5), Zisin, 46, 85–93, 1993 (in Japanese with English abstract).

    Google Scholar 

  • Mogi, T., K. Hongo, and K. Sassa, Electrical properties of fine grained soil, Butsuri Tansa (Geophys. Explor.), 39, 95–105, 1986 (in Japanese with English abstract).

    Google Scholar 

  • Möller, P., S. M. Weise, E. Althaus, W. Bach, H. J. Behr, R. Borchardt, K. Bräuer, J. Drescher, J. Erzinger, E. Faber, B. T. Hansen, E. E. Horn, E. Huenges, H. Kömpf, W. Kessels, T. Kirsten, D. Landwehr, M. Lodemann, L. Machon, A. Pekdeger, H.-U. Pielow, C. Reutel, K. Simon, J. Walther, F. H. Weinlich, and M. Zimmer, Paleofluids and recent fluids in the upper continental crust: results from the German Continental Deep Drilling Program (KTB), J. Geophys. Res., 102, 18233–18254, 1997.

    Article  Google Scholar 

  • Nur, A., Dilatancy, pore fluids and premonitory variations of ts/tp travel times, Bull. Seismol. Soc. Am., 62, 1217–1222, 1972.

    Google Scholar 

  • Ogawa, Y., Deep crustal resistivity structure revealed by wideband magnetotellurics—Tohoku and Hokkaido region-, Ph.D. Thesis, Univ. of Tokyo, 320 pp., 1992.

  • Oide, K, H. Nakagawa, and S. Kanisawa(eds.), Regional Geology of Japan, Part 2 Tohoku, 338 pp., Kyoritsu Shuppan Co., Ltd., 1989 (in Japanese).

  • Olhoeft, G. R., Electrical properties of granite with implications for the lower crust, J. Geophys. Res., 86, 931–936, 1981.

    Article  Google Scholar 

  • Rodi, A technique for improving the accuracy of finite element solutions for magnetotelluric data, Geophys. J. R. Astr. Soc., 44, 483–506, 1976.

    Article  Google Scholar 

  • Shankland, T. J. and M. E. Ander, Electrical conductivity, temperatures, and fluids in the lower crust, J. Geophys. Res., 88, 9475–9484, 1983.

    Article  Google Scholar 

  • Scholz, C. H., L. R. Sykes, and Y. P. Aggarwal, Earthquake prediction: A physical basis, Science, 181, 803–810, 1973.

    Article  Google Scholar 

  • Smith, J. T., Estimating galvanic-distortion magnetic fields in magnetotellurics, Geophys. J. Int., 130, 65–72, 1997.

    Article  Google Scholar 

  • Takagi, A., A. Hasegawa, and N. Umino, Focal mechanism of shallow earthquakes occurring in Tohoku district, northeastern Japan, Program. Abstr. Seismol. Soc. Jpn., No. 1, p. 124, 1973 (in Japanese).

  • Uchida, T., Smooth 2-D inversion for magnetotelluric data based on statistical criterion ABIC, J. Geomag. Geoelectr., 45, 841–858, 1993.

    Article  Google Scholar 

  • Uchida, T. and Y. Ogawa, Development of FORTRAN code for two-dimensional magnetotelluric inversion with smoothness constraint, Open-File Report, Geological Survey of Japan, No. 205, 115 pp., 1993.

  • Utsu, T., Magnitude of earthquakes and occurrence of their aftershocks, Zisin, 10, 6–23, 1957 (in Japanese).

    Google Scholar 

  • Wessel, P. and W. H. F. Smith, New version of the Generic Mapping Tools released, EOS Trans. AGU, 76 (33), 329, 1995.

    Article  Google Scholar 

  • Yamada, N., Y. Teraoka, and M. Hata(Chief eds.), Geological map of Japan, scale 1:1,000,000, Geological Atlas of Japan, Geological Survey of Japan, p. 11, 1982.

  • Zhao, D., H. Kanamori, H. Negishi, and D. Wiens, Tomography of the source area of the 1995 Kobe Earthquake; evidence for fluids at the hypocenter?, Science, 274, 1891–1894, 1996.

    Article  Google Scholar 

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Correspondence to Masahiro Ichiki.

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Ichiki, M., Mishina, M., Goto, T. et al. Magnetotelluric investigations for the seismically active area in Northern Miyagi Prefecture, northeastern Japan. Earth Planet Sp 51, 351–361 (1999). https://doi.org/10.1186/BF03352239

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  • DOI: https://doi.org/10.1186/BF03352239

Keywords

  • Lower Crust
  • Apparent Resistivity
  • Conductive Zone
  • Resistivity Structure
  • Impedance Tensor