Last Update 05/17 2014
Okubo has been involved in the development and application of gravimetric methods for studying earthquake processes of earthquakes and volcanic eruption. He has presented comprehensive formulae on co-seismic gravity changes in various media including the simplest homogeneous elastic half-space and the most sophisticated stratified spherical viscoelastic earth with Wenke SUN, Y. Tanaka and others. Through these theoretical works, the Guy Bomford Prize was awarded to him in 1991 by the International Association of Geodesy (IAG). He stepped further from the theoretical work to field measurement using a state-of-the-art FG5 absolute gravimeters. It was his group that found unambiguous coseismic gravity change for the first time in the world (Tanaka et al., 2001) and very minute far-field gravity signal (Imanishi et al. 2004). Okubo\'s group showed a large-scale lateral movement of magma during the Miyake-jima eruption in 2000 through detailed analysis of absolute gravity change in time and space on the volcano (Furuya et al., 2003). They are awarded with \"Excelent Paper Award\" by the Volcanological Society of Japan, in 2004. Okubo has started integrating gravity and muon radiography studies since 2010 when he was appointed as a Head of the CHEER (Center for High Energy gEophysics Research).One of the most recent result can be found in 3-D density imaging of a lava dome (Nishiyama et al., 2013).
古屋正人・大久保修平・田中愛幸・孫文科・渡辺秀文・及川純・前川徳光, 重力の時間変化でとらえた三宅島2000年火山活動におけるカルデラ形成過程, 地学雑誌, 110, 2, 217--225, 2001.
Tanaka, Y., S. Okubo, M. Machida, I. Kimura, and T. Kosuge, First detection of absolute gravity change caused by earthquake, Geophys. Res. Lett., 28, 15, 2979--2981, 2001.
Furuya, M., S, Okubo, F. Kimata, R. Miyajima, I. Meilano, W. Sun, Y. Tanaka1, and T. Miyazaki, Mass budget of the magma flow in the 2000 volcano-seismic activity at Izu-islands, Japan, Earth Planets Space, 55, 7, 375--385, 2003.
Furuya, M., S. Okubo, W. Sun, Y. Tanaka, J. Oikawa, H. Watanabe, and T. Maekawa, Spationtemporal gravity changes at Miyakejima volcano, Japan: Caldera collapse, explosive eruptions and magma movement, J. Geophys. Res., 108, B4, 2219, doi:10.1029/2002JB001989, , 2003.
Imanishi, Y., T. Sato, T. Higashi, W. Sun and S. Okubo, A Network of SuperconductingGravimeters Detects Submicrogal Coseismic Gravity Changes, Science, 306, 5695, 476--478, 2004.
Sun W., and S. Okubo, Coseismic deformations detectable by satellite gravity missions: A case study of Alaska (1964, 2002) and Hokkaido (2003) earthquakes in the spectral domain, J. Geophys. Res., 109, B04405, doi:10.1029/2003JB02554, , 2004.
大久保修平, 重力変化から火山活動を探る−観測・理論・解析, 火山, 50, 50周年特別, S49--S58, 2005.
Tanaka, Y., J. Okuno and S. Okubo, A new method for the computation of global viscoelastic post-seismic deformation in a realistic earth model (I)—vertical displacement and gravity variation, Geophys. J. Int., 164, 2, 273--289, 2006.
Tanaka, Y., J. Okuno and S. Okubo, A new method for the computation of global viscoelastic post-seismic deformation in a realistic earth model (II)-horizontal displacement, Geophys. J. Int., 170, 3, 1031--1052, 2007.
Kazama T. and S. Okubo, Hydrological modeling of groundwater disturbances to observed gravity: Theory and application to Asama Volcano, Central Japan, J. Geophys. Res., 114, B08402, doi:1029/2009JB006391, , 2009.
Okubo, S. and HKM. Tanaka, Imaging the density profile of a volcano interior with cosmic-ray muon radiography combined with classical gravimetry, Meas. Sci. Technol., 23, 4, doi:10.1088/0957-0233/23/4/042001, , 2012.
Okubo, S., T. Kazama, K. Yamamoto, M. Iguchi,Y. Tanaka, T. Sugano, Y. Imanishi, W. Sun, M. Saka, A. Watanabe and S. Matsumoto, Absolute Gravity Variation at Sakurajima Volcano from April 2009 through January 2011 and its Relevance to the Eruptive Activity of Showa Crater, Bull. Volcanol. Soc. Japan, 58, 1, 153--162, 2013.
Okubo, S., Y. Tanaka, S. Ueki, H. Oshima, T. Maekawa and Y. Imanishi, Gravity variation around Shinmoe-dake volcano from February 2011 through March 2012 - Results of continuous absolute gravity observation and repeated hybrid gravity measurements, Earth Planets Space, 65, 6, 563--571, 2013.
Nishiyama, R. , Y. Tanaka, S. Okubo, H. Oshima, H. K. M. Tanaka and T. Maekawa, Integrated processing of muon radiography and gravity anomaly data toward the realization of high-resolution 3D density structural analysis of volcanoes: case study of Showa-Shinzan lava dome, Usu, Japan., J. Geophys. Res., 119, 1, 10.1002/2013JB010234, , 2014.