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A method for simultaneous velocity and density inversion and its application to exploration of subsurface structure beneath Izu-Oshima volcano, Japan
Earth, Planets and Spacevolume 54, pages803–817 (2002)
We have developed a method for three-dimensional simultaneous velocity and density inversion using traveltimes of local earthquakes and gravity data. The purpose of this method is to constrain the velocity inversion and increase the spatial resolution of shallow velocity structures by introducing additional gravity data. The gravity data contributes to the P- and S-wave velocity models by imposing constraints between seismic velocities and density. The constraint curve is constructed so as to fit the data for porous rock samples, and deviations from the curve are taken into account in the inversion. The constraint is imposed at only the first layer, because density structure is well resolved at shallower parts and it is difficult to determine uniquely at greater depths. Synthetic inversion tests indicate that gravity data can improve the resolution of the velocity models for this layer. The method is applied to investigate the subsurface structure of Izu-Oshima volcano, Japan and velocity structures with high spatial resolution are obtained. The additional gravity data contribute primarily to improvement of the S-wave velocity model. At 0.25 km depth, a high velocity anomaly due to caldera-filling lava flows is observed. At 1.25 and 2.5 km depths, high velocity intrusive bodies are detected. A NW-SE trending high velocity belt at 1.25 km depth is interpreted as being caused by repeated intrusion of dikes.
Ando, J., H. Watanabe, and S. Sakashita, Study of gravity anomaly on and around Izu-Oshima volcano, Bull. Earthq. Res. Inst., Univ. Tokyo, 69, 309–350, 1994 (in Japanese with English abstract).
Aramaki, S. and T. Fujii, Petrological and geological model of the 1986–1987 eruption of Izu-Oshima volcano, Bull. Volcanol. Soc. Japan, 33, S297–S306, 1988 (in Japanese with English abstract).
Birch, F., The velocity of compressional waves in rocks to 10 kilobars, part 2, J. Geophys. Res., 66, 2199–2224, 1961.
Gardner, G. H. F., L. W. Gardner, and A. R. Gregory, Formation velocity and density—The diagnostic basics for stratigraphic traps, Geophysics, 39, 770–780, 1974.
Hasegawa, I., K. Ito, K. Ono, T. Aihara, K. Kusunose, and T. Satoh, Crustal structure of Izu-Oshima island revealed by explosion seismic measurements—A profile across the island, Bull. Geol. Surv. Japan, 38, 741–753, 1987 (in Japanese with English abstract).
Hashimoto, M. and T. Tada, Crustal deformations before and after the 1986 eruption of Izu-Oshima volcano, Bull. Volcanol. Soc. Japan, 33, S136–S144, 1988 (in Japanese with English abstract).
Ida, Y., Magma chamber and eruptive processes at Izu-Oshima volcano, Japan: buoyancy control of magma migration, J. Volcanol. Geotherm. Res., 66, 53–67, 1995.
Ida, Y., K. Yamaoka, and H. Watanabe, Underground magmatic activities associated with the 1986 eruption of Izu-Oshima volcano, Bull. Volcanol. Soc. Japan, 33, S307-S318, 1988 (in Japanese with English abstract).
Ito, K., Cutoff depth of seismicity and large earthquakes near active volcanoes in Japan, Tectonophys., 217, 11–21, 1993.
Jackson, D. D. and M. Matsu’ura, A Bayesian approach to nonlinear inversion, J. Geophys. Res., 90, 581–591, 1985.
Kato, S. and Seabottom Survey Group around O-Sima Volcano after 1986 Eruption, Seabottom survey around O-sima island of Izu-Ogasawara arc, Report of Hydrographic Researches, 23, 177–185, 1987 (in Japanese with English abstract).
Lee, W. H. K. and S. W. Stewart, Principles and applications of microearthquake networks, Adv. Geophys. Suppl. 2, 293 pp., 1981.
Lees, J. M. and J. C. VanDecar, Seismic tomography constrained by Bouguer gravity anomalies: Applications in Western Washington, PA-GEOPH, 135, 31–52, 1991.
Ludwig, W. J., J. E. Nafe, and C. L. Drake, Seismic refraction, in The Sea, Vol. 4, edited by A. E. Maxwell, pp. 53–84, Wiley Interscience, New York, 1970.
Makino, M., T. Nakatsuka, S. Okuma, and T. Kaneko, Aeromagnetic anomalies over the Izu-Oshima volcano, Bull. Volcanol. Soc. Japan, 33, S217–S223, 1988 (in Japanese with English abstract).
Mikada, H., An Elastic Scattering Theory and Its Application to the Understanding of Subsurface Structure of Izu-Oshima Volcano, PhD thesis, University of Tokyo, 159 pp., 1994.
Mikada, H., H. Watanabe, and S. Sakashita, Evidence for subsurface magma bodies beneath Izu-Oshima volcano inferred from a seismic scattering analysis and possible interpretation of the magma plumbing system of 1986 eruptive activity, Phys. Earth Planet. Int., 104, 257–269, 1997.
Nafe, J. E. and C. L. Drake, Physical properties of marine sediments, in The Sea, Vol. 3, edited by M. N. Hill, pp. 794–815, Interscience, New York, 1963.
Nagy, D., The gravitational attraction of a right rectangular prism, Geophysics, 31, 362–371, 1966.
Nakamura, K., Volcano-stratigraphic study of Oshima volcano, Izu, Bull. Earthq. Res. Inst, Univ. Tokyo, 42, 649–728, 1964.
Nakamura, K., Volcanoes as possible indicators of tectonic stress orientation—Principle and proposal, J. Volcanol. Geotherm. Res., 2, 1–16, 1977.
Nakamura, K., K. Shimazaki, and N. Yonekura, Subduction, bending and eduction. Present and Quaternary tectonics of the northern border of the Philippine Sea plate, Bull. Soc. Feol. France, 26, 221–243, 1984.
Okubo, P. G., H. M. Benz, and B. A. Chouet, Imaging the crustal magma sources beneath MaunaLoa and Kilauea volcanoes, Hawaii, Geology, 25, 867–870, 1997.
Sakashita, S., T Shimomura, H. Mikada, and H. Watanabe, Volcano monitoring at Izu-Oshima Volcano Observatory, Earthquake Research Institute, University of Tokyo, Tech. Res. Rep., Earthq. Res. Inst., Univ. of Tokyo, 7–17, 1996 (in Japanese with English abstract).
Scales, J. A., Tomographic inversion via the conjugate gradient method, Geophysics, 52, 179–185, 1987.
Suyehiro, K., N. Takahashi, Y. Ariie, Y. Yokoi, R. Hino, M. Shinohara, T. Kanazawa, N. Hirata, H. Tokuyama, and A. Taira, Continental crust, crustal underplating, and low-Q upper mantle beneath an oceanic island arc, Science, 272, 390–392, 1996.
Talwani, M., Computer usage in the computation of gravity anomalies, in Method in Computational Physics: Advances in Research and Applications; Vol. 13, edited by B. A. Bolt, 473 pp., Academic Press, New York, 1973.
Thurber, C. H., Earthquake locations and three-dimensional crustal structure in the Coyote Lake Area, Central California, J. Geophys. Res., 88, 8226–8236, 1983.
Um, J. and C. Thurber, A fast algorithm for two-point seismic ray tracing, Bull. Seismol Soc. Am., 77, 972–986, 1987.
Watanabe, H., Precursors to eruption and volcano prediction, Bull. Volcanol. Soc. Japan, 34, S215–S226, 1990 (in Japanese).
Watanabe, H., Precursors to the 1986 eruption and the magma plumbing system of Izu-Oshima volcano, Bull. Volcanol. Soc. Japan, 43, 271–282, 1998 (in Japanese with English abstract).
Watanabe, H., Borehole density data in the caldera of Izu-Oshima volcano, unpublished.
Yakiwara, H. and H. Shimizu, Three dimensional velocity structure of crust and upper mantle under the volcanoes, Kyushu, Prog. Abst. Volcanol. Soc. Japan, 1997 (in Japanese).
Yamamoto, K., Three-Dimensional P-wave Velocity Structure of Izu-Oshima Volcano, Japan by Using Teleseismic Data: for Detection of Magma Reservoir, Master’s thesis, University of Tokyo, 52 pp., 1993.
Yamaoka, K., H. Watanabe, and S. Sakashita, Seismicity during the 1986 eruption of Izu-Oshima volcano, Bull. Volcanol. Soc. Japan, 33, S91–S101, 1988 (in Japanese with English abstract).