Open Access3-D Gravity Basement Structure Around Mashiki, Kumamoto, Japan
Author(s) -
Shun Araki,
Tatsuya Noguchi,
Masao Komazawa,
Shoya Arimura,
Mitsuhiro Tamura,
Kei Nakayama,
Hitoshi Morikawa,
Takashi Miyamoto,
Kahori Iiyama,
Yoshiya Hata,
Masayuki Yoshimi,
Takao Kagawa,
Hiroyuki Goto
Publication year - 2018
Publication title -
journal of disaster research
Language(s) - English
Resource type - Journals
eISSN - 1883-8030
pISSN - 1881-2473
DOI - 10.20965/jdr.2018.p0193
Subject(s) - graben , bouguer anomaly , geology , seismology , basement , gravity anomaly , horst and graben , anomaly (physics) , density contrast , geodesy , geomorphology , geophysics , tectonics , paleontology , geography , physics , archaeology , condensed matter physics , astronomy , oil field
Gravity survey has been carried out around central part of Mashiki, Kumamoto, Japan, where was severely damaged by 2016 Kumamoto earthquake. Dense observations were performed at more than 450 sites around the central part of Mashiki. The observation sites satisfy enough density to discuss density structure shallower than 500-meter depth around the target area. After applying some corrections to the observed data, Bouguer anomaly is obtained and three dimensional model of gravity basement is estimated. As a result, a graben runs parallel to the Akitsukawa River and some isolated small basins are found inside of the graben. The central part of Mashiki is located immediately above of the one of such the small basins. We also analyze focusing and defocusing effects of ray of seismic wave under very simple assumptions and it is found that the central part of Mashiki locates close to a focusing area.