Masahiro Korenaga
Railway Technical Research Institute
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Publication
Featured researches published by Masahiro Korenaga.
Earth, Planets and Space | 2005
Takuo Shibutani; Yoshihisa Iio; Satoshi Matsumoto; Hiroshi Katao; Takeshi Matsushima; Shiro Ohmi; Fumiaki Takeuchi; Kenji Uehira; Kin’ya Nishigami; Bogdan Enescu; Issei Hirose; Yasuyuki Kano; Yuhki Kohno; Masahiro Korenaga; Yutaka Mamada; Masatoshi Miyazawa; Ken’ichi Tatsumi; Tomotake Ueno; Hiroo Wada; Yohei Yukutake
The 2004 Mid Niigata Prefecture Earthquake (Mj = 6.8) occurred on 23 October 2004 in the northeastern part of the Niigata-Kobe Tectonic Zone where large contraction rates were observed. The mainshock was followed by an anomalously intense aftershock activity that included nine Mj ≥5.5 aftershocks. We deployed three temporary online seismic stations in the aftershock area from 27 October, combined data from the temporary stations with those from permanent stations located around the aftershock area, and determined the hypocenters of the mainshock and aftershocks with a joint hypocenter determination (JHD) technique. The resulting aftershock distribution showed that major events such as the mainshock, the largest aftershock (Mj = 6.5), the aftershock on 27 October (Mj = 6.1), etc. occurred on different fault planes that were located nearly parallel or perpendicular to each other. This might be due to heterogeneous structure in the source region. The strain energy was considered to have been enough accumulated on the individual fault planes. These features are probably a cause of the anomalous intensity of the aftershock activity.
Earth, Planets and Space | 2005
Masahiro Korenaga; Satoshi Matsumoto; Yoshihisa Iio; Takeshi Matsushima; Kenji Uehira; Takuo Shibutani
The 2004 mid Niigata prefecture earthquake with M6.8 occurred in the north of central part of Japan. It was a reverse fault by the regional compression stress field in NW-SE direction. Several aftershocks with M≥6 were occurred. The large aftershocks occurred on plural fault planes. The plane was either parallel or normal to the main shock one. We estimated three dimensional velocity structures in and around the focal area of the earthquake by using a Double Difference tomography method. The arrival time data were picked from seismograms at the deployed seismic stations settled by Kyoto and Kyushu universities in collaboration, NIED, ERI, and JMA. The velocity structure showed that a low velocity zone existed in the northwest part of the aftershock area. On the contrary, the velocity in the southeast became high. Moreover, the fault plane of the main shock inferred from the aftershock distribution was located at the velocity boundary.
Earth, Planets and Space | 2012
Shunta Noda; Shunroku Yamamoto; Shinji Sato; Naoyasu Iwata; Masahiro Korenaga; Kimitoshi Ashiya
We propose a new approach to improve the accuracy of the back-azimuth estimation in real-time by using a single station record. Compared with the conventional approach in which the length of the time window for the analysis is fixed for all data, the accuracy and speed of the estimation are drastically improved by introducing a variable-length time window which is determined by the first half cycle of the wavelength of the initial P -wave, because this window tends to reduce the influences of trailing scattered waves. The analysis, using the K-NET dataset, shows that the estimation, using this new approach, is improved by 28% and 0.25 s in accuracy and speed, respectively.
Butsuri-tansa(geophysical Exploration) | 2007
Kimitoshi Ashiya; Shinji Sato; Naoyasu Iwata; Masahiro Korenaga; Hiromitsu Nakamura
Quarterly Report of Rtri | 2015
Naoyasu Iwata; Shunroku Yamamoto; Masahiro Korenaga; Shunta Noda
Archive | 2009
Masahiro Korenaga; 将宏 是永
Earth, Planets and Space | 2017
Seiji Tsuno; Masahiro Korenaga; Kyosuke Okamoto; Hiroaki Yamanaka; Kosuke Chimoto; Takeshi Matsushima
Archive | 2009
Masahiro Korenaga; 将宏 是永
Quarterly Report of Rtri | 2011
Shunroku Yamamoto; Shinji Sato; Naoyasu Iwata; Masahiro Korenaga; Yoshiaki Ito; Shunta Noda
Archive | 2011
Naoyasu Iwata; Shunroku Yamamoto; Masahiro Korenaga; 俊六 山本; 直泰 岩田; 将宏 是永