A5101692791- earthquake and tectonic studies
- Seismology and Earthquake Studies
- High-pressure geophysics and materials
- Seismic Waves and Analysis
- Geological and Geochemical Analysis
- Methane Hydrates and Related Phenomena
- Earthquake Detection and Analysis
- Seismic Imaging and Inversion Techniques
- Tropical and Extratropical Cyclones Research
- Radioactive contamination and transfer
- Photonic Crystal and Fiber Optics
- Coastal and Marine Management
- Advanced Fiber Laser Technologies
- Underwater Vehicles and Communication Systems
- Advanced Computational Techniques and Applications
- Ocean Waves and Remote Sensing
- Geophysics and Sensor Technology
- Coastal and Marine Dynamics
- Geographic Information Systems Studies
- Earthquake and Disaster Impact Studies
- Disaster Management and Resilience
- Underwater Acoustics Research
- Advanced Fiber Optic Sensors
- Geology and Paleoclimatology Research
- Random lasers and scattering media
Japan Meteorological Agency
2007-2021
Japan Agency for Marine-Earth Science and Technology
2004-2019
Schlumberger (British Virgin Islands)
2018
Tohoku University
2008-2012
Akita Industrial Technology Center
2001
A magnitude 7.3 foreshock occurred at the subducting Pacific plate interface on March 9, 2011, 51 h before 9.0 Tohoku earthquake off coast of Japan. We propose a coseismic and postseismic afterslip model event based global positioning system network ocean bottom pressure gauge sites. The estimated slip areas show complementary spatial distributions; distribution is located up‐dip for northward hypocenter earthquake. amount roughly consistent with that determined by repeating analysis carried...
A low-velocity zone (LVZ) has been detected by seismic exploration surveys within the Nankai accretionary prism toe off Kii Peninsula, southwestern Japan, and is considered to be a mechanically weak volume at depth. Such mechanical heterogeneities potentially influence tsunamigenic slips on megathrust earthquakes in subduction zone. However, spatial distribution of LVZ along trough-parallel direction still elusive. Here we show sporadic LVZs from one-dimensional shear wave velocity (Vs)...
We have detected an event of pore pressure change (hereafter, we refer it to “pore event”) from borehole stations in real time March 2020, owing the network developed by connecting three Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) observatories near Nankai Trough. During event, shallow very low-frequency events (sVLFEs) were also broadband seismometers DONET, which suggests that sVLFE migrated toward updip region along subduction plate boundary. Since one sensors...
We detected long-term hydrostatic pressure changes at ocean-bottom stations of the Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET) along Nankai trough, off southwestern Japan. these after removing contributions ocean mass variations sensor drift from records. In addition, we a decrease in background seismicity rate nearby earthquake cluster that was synchronous with changes. interpreted observed to reflect vertical deformation floor 3–8 cm, consider cause seafloor...
The distribution of aftershocks a large ( M w = 7.0) normal faulting earthquake beneath the outer slope Japan Trench in 2005, measured 2007 using ocean bottom seismographs, indicates that was involved with set conjugate faults. Although faults reach to upper mantle, estimated Vp and Vp/Vs show no remarkable changes can be related extensive hydration crust or uppermost mantle. absence horst‐graben topographic structure rupture area suggests immaturity bending fault system is responsible for...
Megathrust earthquakes have occurred repeatedly at intervals of 100 to 150 years along the Nankai Trough, situated in southwest Japan. Given that it has been 70 since last event, occurrence next devastating earthquake is anticipated near future. On April 1, 2016, a moderate (Mw 5.9, MJMA 6.5) off southeastern coast Mie Prefecture source region 1944 Tonankai 8.2). In this study, we investigated influence 2016 on future megathrust earthquakes. We first determined hypocenter distributions using...
We relocated hypocenters of the foreshock, mainshock, and aftershocks 2011 off Pacific coast Tohoku earthquake (M 9.0) in middle part Japan Trench where rupture initiated. Ocean Bottom Seismographs (OBSs), deployed area, recorded earthquakes these data provide improved images hypocenter distribution. The mainshock was slightly westward from that reported by Meteorological Agency (JMA), placing it near intersection between plate boundary Moho overriding plate. foreshock seismicity mainly...
We performed 3‐D seismic tomography in the forearc region of northeastern Japan subduction zone using both onshore and offshore station data. obtained Vp , Vs / structures around plate boundary with high spatial resolution. The position as defined by relocated hypocenters coincides sharp velocity between oceanic crust mantle wedge. wedge above coseismic slip area 1978 2005 off‐Miyagi interplate earthquakes (M > 7) is characterized but low . Off Fukushima, however, where large rarely...
Summary Fiber-optic technology, such as distributed acoustic sensing (DAS) and hybrid logging cable, can significantly reduce operating time for obtaining a 3D vertical seismic profile (VSP) survey by combining it with conventional borehole arrays to record high-resolution three-component (3C) images at reservoir depths valuable time-depth velocity data one-component (1C) imaging within the overburden from fiber optic cable. The first field application of heterodyne vibration (hDVS) DAS...
Hypocenter distribution of the 2005 Miyagi-oki earthquake (M 7.2) and its aftershocks were relocated by using ocean bottom seismographic (OBS) data. The mainshock was observed 14 OBSs which deployed in focal area about one month prior to occurrence. Additional 16 for aftershock observations. Relocated hypocenters concentrate along a landward dipping plane whose location dip angle correspond well plate boundary defined previous study. Although most significant activity concentrates around...
One of the observation targets Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET), which deployed in Nankai trough, is monitoring crustal deformations caused by ordinary earthquakes, low frequency earthquake slow slip event. Although it possible that vertical are measured using quarts type pressure gauge on oceanfloor, changes recorded those sensors include several kinds signals such as ocean surface sensor drift other than deformations. We estimated component deformation...
Abstract The deployment of real-time permanent ocean-bottom seismic and tsunami observatories is significant for disaster mitigation prevention during the occurrence large subduction earthquakes near trough areas. On April 1, 2016, a moderate-sized suboceanic earthquake occurred beneath Dense Oceanfloor Network System Earthquakes Tsunamis (DONET) stations that were recently deployed in deep areas Nankai Trough southwest Japan. P-waves arrived at station within 4 s origin time, which was 6 13...