Three-dimensional gravity inversion using automatic regional-residual components separation with application to the Iwaki area in Fukushima Prefecture, Japan
Yasuaki MurataFukushima Renewable Energy Institute, AIST (FREA), 2-2-9 Machiikedai, Koriyama, Fukushima 963-0298, Japan. Email: murata.gsj@aist.go.jp
Exploration Geophysics 49(4) 584-594 https://doi.org/10.1071/EG17085
Submitted: 26 June 2017 Accepted: 5 July 2017 Published: 12 September 2017
Abstract
We have developed a simple method for analysing gravity data to define 3D subsurface structures consistent with geological maps and reflection seismic survey results. This new method makes it possible to automatically separate gravity anomalies caused by structures that are the target of analysis (residual gravity) and not subject to gravity anomaly analysis (trend surfaces or regional gravity variations). This separation is achieved by assuming that the gravity anomaly trend surface is extremely smooth prior to analysis. In addition, this analysis can be carried out automatically, so it is possible to use a boot-strap simulation to evaluate the effect that gravity data accuracy and survey point distribution have on the analysis results. Using this newly developed method, we conducted a 3D subsurface structural analysis based on newly obtained gravity survey data in an area around Iwaki City, Fukushima Prefecture. The results of the 3D structural analysis revealed sharp depressions in the basement rock and basin-shaped underground structures along the Yunodake and Yamada faults. Finally, we were able to estimate the influence of survey point distribution and abrupt changes in the structure on the analysis results using a boot-strap simulation of the 3D analysis.
Key words: three-dimensional structure, boot-strap simulation, Fukushima Prefecture, gravity survey, Idosawa Fault, Iwaki City, regional-residual separation, Yunodake Fault.
References
Awata, Y., Kagohara, K., Sugiyama, Y., Yoshioka, T., Azuma, T., Ando, K., and Maruyama, T., 2011, Slip vectors of the surface faulting along the Yunotake and Fujiwara faults associated with the earthquake of April 11, 2011, SE Fukushima Prefecture: Report of Coordinating Committee for Earthquake Prediction, 86, 170–172.Cordell, L., and Henderson, R. G., 1968, Iterative three-dimensional solution of gravity anomaly data using a digital computer: Geophysics, 33, 596–601
| Iterative three-dimensional solution of gravity anomaly data using a digital computer:Crossref | GoogleScholarGoogle Scholar |
Geological Survey of Japan (eds.) 1957, Geological map and explanatory text of the Joban Coal Field: Geological maps of coal fields of Japan, 1, Geological Survey of Japan, AIST.
Geological Survey of Japan (eds.) 2013, Gravity database of Japan, DVD edition: Digital geoscience map, P-2, Geological Survey of Japan, AIST.
Inoue, H., 1986, A least-squares smooth fitting for irregularly spaced data: finite-element approach using the cubic B-spline basis: Geophysics, 51, 2051–2066
| A least-squares smooth fitting for irregularly spaced data: finite-element approach using the cubic B-spline basis:Crossref | GoogleScholarGoogle Scholar |
Komazawa, M., 1995, Gravimetric analysis of Aso volcano and its interpretation: Journal of the Geodetic Society of Japan, 41, 17–45
| Gravimetric analysis of Aso volcano and its interpretation:Crossref | GoogleScholarGoogle Scholar |
Kubo, K., Yanagisawa, Y., Yamamoto, T., Nakae, S., Takahashi, H., Toshimitsu, S., Banno, Y., Miyachi, Y., Takahashi, M., Komazawa, M., and Ohno, T., 2007, Geological map of Japan 1 : 200,000, Shirakawa: Geological Survey of Japan, AIST.
Li, Y., and Oldenburg, D. W., 1998, Separation of regional and residual magnetic field data: Geophysics, 63, 431–439
| Separation of regional and residual magnetic field data:Crossref | GoogleScholarGoogle Scholar |
Mickus, K. L., Aiken, C. L. V., and Kennedy, W. D., 1991, Regional-residual gravity anomaly separation using the minimum-curvature technique: Geophysics, 56, 279–283
| Regional-residual gravity anomaly separation using the minimum-curvature technique:Crossref | GoogleScholarGoogle Scholar |
Murata, Y., 1993, Estimation of optimum average surficial density from gravity data: an objective Bayesian Approach: Journal of Geophysical Research, 98, 12097–12109
| Estimation of optimum average surficial density from gravity data: an objective Bayesian Approach:Crossref | GoogleScholarGoogle Scholar |
Murata, Y., and Noro, H., 1993, Optimization of estimation procedure of Bouguer density by use of the ABIC-minimization method: Butsuri Tansa (Geophysical Exploration), 46, 120–127
Murata, Y., Matsumoto, N., Okada, C., and Takahashi, Y., 2013, Gravity survey data of Iwaki Area, Fukushima Prefecture: AIST Open-File Report, no. 585, 74 pp., 1 CD-ROM, Geological Survey of Japan, AIST.
Nagihara, S., and Hall, S. A., 2001, Three-dimensional gravity inversion using simulated annealing: Constraints on the diapiric roots of allochthonous salt structures: Geophysics, 66, 1438–1449
| Three-dimensional gravity inversion using simulated annealing: Constraints on the diapiric roots of allochthonous salt structures:Crossref | GoogleScholarGoogle Scholar |
Nawa, K., Fukao, Y., Shichi, R., and Murata, Y., 1997, Inversion of gravity data to determine the terrain density distribution in southwest Japan: Journal of Geophysical Research, 102, 27703–27719
| Inversion of gravity data to determine the terrain density distribution in southwest Japan:Crossref | GoogleScholarGoogle Scholar |
Nettleton, L. L., 1976, Gravity and magnetics in oil prospecting: McGraw-Hill.
Suda, Y., Murata, Y., Kikuchi, T., and Hanaoka, N., 1991, Physical Properties Data-Base System of Rocks (PROCK): GSJ Open-File Report, no.155, 231 pp., Geological Survey of Japan, AIST.
Tsutsumi, H., and Toda, S., 2012, Surface rupture associated with the April 11, 2011 Fukushima-ken Hamadori earthquake and paleoseismic history of the causative fault: Journal of the Geological Society of Japan, 118, 559–570
| Surface rupture associated with the April 11, 2011 Fukushima-ken Hamadori earthquake and paleoseismic history of the causative fault:Crossref | GoogleScholarGoogle Scholar |
Uchida, T., and Ueda, T., 2013, Electromagnetic survey over Yunodake and Itozawa Faults in Iwaki area, Fukushima Prefecture, Reports of Research and Investigation on Multiple Geological Hazards Caused by Huge Earthquakes: GSJ Interim Report, no. 66, 103–112.
Yamaguchi, K., Ito, S., and Kano N., 2013, Integrated seismic survey of reflection and refraction method in Iwaki area, Fukushima Prefecture, Reports of Research and Investigation on Multiple Geological Hazards Caused by Huge Earthquakes: GSJ Interim Report, no. 66, 83–102.