Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan

2017 ◽  
Vol 44 (15) ◽  
pp. 7766-7772 ◽  
Author(s):  
Azusa Shito ◽  
Satoshi Matsumoto ◽  
Hiroshi Shimizu ◽  
Takahiro Ohkura ◽  
Hiroaki Takahashi ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Seismic Velocity ◽  
Source Region ◽  
Earthquake Sequence ◽  
2016 Kumamoto Earthquake ◽  
Seismic Velocity Structure ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake

scholarly journals Seismic velocity structure at the southern termination of the 2016 Kumamoto Earthquake rupture, Japan

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Yasuhira Aoyagi ◽  
Haruo Kimura ◽  
Kazuo Mizoguchi
Keyword(s):  
Fault Zone ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Earthquake Rupture ◽  
2016 Kumamoto Earthquake ◽  
Seismic Velocity Structure ◽  
Kumamoto Earthquake ◽  
Seismogenic Layer ◽  
The 2016 Kumamoto Earthquake ◽  
Tectonic Line

Abstract The earthquake rupture termination mechanism and size of the ruptured area are crucial parameters for earthquake magnitude estimations and seismic hazard assessments. The 2016 Mw 7.0 Kumamoto Earthquake, central Kyushu, Japan, ruptured a 34-km-long area along previously recognized active faults, eastern part of the Futagawa fault zone and northernmost part of the Hinagu fault zone. Many researchers have suggested that a magma chamber under Aso Volcano terminated the eastward rupture. However, the termination mechanism of the southward rupture has remained unclear. Here, we conduct a local seismic tomographic inversion using a dense temporary seismic network to detail the seismic velocity structure around the southern termination of the rupture. The compressional-wave velocity (Vp) results and compressional- to shear-wave velocity (Vp/Vs) structure indicate several E–W- and ENE–WSW-trending zonal anomalies in the upper to middle crust. These zonal anomalies may reflect regional geological structures that follow the same trends as the Oita–Kumamoto Tectonic Line and Usuki–Yatsushiro Tectonic Line. While the 2016 Kumamoto Earthquake rupture mainly propagated through a low-Vp/Vs area (1.62–1.74) along the Hinagu fault zone, the southern termination of the earthquake at the focal depth of the mainshock is adjacent to a 3-km-diameter high-Vp/Vs body. There is a rapid 5-km step in the depth of the seismogenic layer across the E–W-trending velocity boundary between the low- and high-Vp/Vs areas that corresponds well with the Rokkoku Tectonic Line; this geological boundary is the likely cause of the dislocation of the seismogenic layer because it is intruded by serpentinite veins. A possible factor in the southern rupture termination of the 2016 Kumamoto Earthquake is the existence of a high-Vp/Vs body in the direction of southern rupture propagation. The provided details of this inhomogeneous barrier, which are inferred from the seismic velocity structures, may improve future seismic hazard assessments for a complex fault system composed of multiple segments.

scholarly journals Geotechnical and infrastructural damage due to the 2016 Kumamoto earthquake sequence

2018 ◽  
Vol 104 ◽  
pp. 390-394 ◽  
Author(s):  
S. Bhattacharya ◽  
M. Hyodo ◽  
G. Nikitas ◽  
B. Ismael ◽  
H. Suzuki ◽  
...  
Keyword(s):  
Earthquake Sequence ◽  
2016 Kumamoto Earthquake ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake

scholarly journals Strong motions observed by K-NET and KiK-net during the 2016 Kumamoto earthquake sequence

2017 ◽  
Vol 69 (1) ◽  
Author(s):  
Wataru Suzuki ◽  
Shin Aoi ◽  
Takashi Kunugi ◽  
Hisahiko Kubo ◽  
Nobuyuki Morikawa ◽  
...  
Keyword(s):  
Earthquake Sequence ◽  
2016 Kumamoto Earthquake ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake

scholarly journals Electrical conductive fluid-rich zones and their influence on the earthquake initiation, growth, and arrest processes: Observations from the 2016 Kumamoto earthquake sequence, Kyushu Island, Japan

2020 ◽  
Author(s):  
Koki Aizawa ◽  
Shinichi Takakura ◽  
Hisafumi Asaue ◽  
Katsuaki Koike ◽  
Ryokei Yoshimura ◽  
...  
Keyword(s):  
Broad Band ◽  
Quantitative Relationship ◽  
Outer Edge ◽  
Earthquake Sequence ◽  
2016 Kumamoto Earthquake ◽  
Magnetotelluric Data ◽  
Kumamoto Earthquake ◽  
Crustal Earthquakes ◽  
The 2016 Kumamoto Earthquake ◽  
Earthquake Ruptures

Abstract Crustal earthquake ruptures tend to initiate near fluid-rich zones. However, it is relatively unknown whether fluid-rich zones can further promote or arrest these ruptures. We image the electrical resistivity structure around the focal area of the 2016 Kumamoto earthquake sequence by using 200 sites broad-band magnetotelluric data, and discuss its quantitative relationship to earthquake initiation, growth, and arrest processes. The ruptures that initiated along the outer edge of the low-resistivity fluid-rich zones (<30 Ωm) tended to become large earthquakes, whereas those that initiated either distal to or within the fluid-rich zones did not. The ruptures were arrested by high-temperature (>400°C) fluid-rich zones, whereas shallower low-temperature (200–400°C) fluid-rich zones either promoted or arrested the ruptures. These results suggest that the distribution of mid-crustal fluids contributes to the initiation, growth, and arrest of crustal earthquakes. The pre-failure pressure/temperature gradient (spatial difference) of the pore fluids may contribute to the rupture initiation, propagation, and arrest.

scholarly journals Characteristics of the surface ruptures associated with the 2016 Kumamoto earthquake sequence, central Kyushu, Japan

2016 ◽  
Vol 68 (1) ◽  
Author(s):  
Yoshiki Shirahama ◽  
Masayuki Yoshimi ◽  
Yasuo Awata ◽  
Tadashi Maruyama ◽  
Takashi Azuma ◽  
...  
Keyword(s):  
Earthquake Sequence ◽  
2016 Kumamoto Earthquake ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Surface Ruptures
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