A5084230560- earthquake and tectonic studies
- Seismology and Earthquake Studies
- Seismic Waves and Analysis
- High-pressure geophysics and materials
- Earthquake Detection and Analysis
- Geological and Geochemical Analysis
- Seismic Imaging and Inversion Techniques
- Geophysics and Sensor Technology
- Methane Hydrates and Related Phenomena
- Oceanographic and Atmospheric Processes
- Ocean Waves and Remote Sensing
- Geological and Geophysical Studies
- Earthquake and Disaster Impact Studies
- Seismic Performance and Analysis
- Acoustic Wave Phenomena Research
- Meteorological Phenomena and Simulations
- Speech and Audio Processing
- Earthquake and Tsunami Effects
- Underwater Acoustics Research
- Arctic and Antarctic ice dynamics
- Tropical and Extratropical Cyclones Research
- Geology and Paleoclimatology Research
- Radar Systems and Signal Processing
- Coastal and Marine Dynamics
- Advanced Fiber Optic Sensors
The University of Tokyo
2015-2024
Tokyo University of Information Sciences
2024
Earthquake Engineering Research Institute
2013-2023
Association for the Development of Earthquake Prediction
2008-2023
Tama Art University
2023
Nagoya University
2012-2022
Nagoya Medical Center
2022
National Hospital Organization
2022
National Research Institute for Earth Science and Disaster Resilience
2020-2021
Bunkyo University
2021
Tsunami waveform inversion for the 11 March, 2011, off Pacific coast of Tohoku Earthquake (M 9.0) indicates that source largest tsunami was located near axis Japan trench. Ocean-bottom pressure, and GPS wave, gauges recorded two-step waveforms: a gradual increase sea level (~2 m) followed by an impulsive wave (3 to 5 m). The slip distribution estimated from 33 coastal tide gauges, offshore bottom-pressure show large slip, more than 40 m, along trench axis. This similar but much larger 1896...
The 2011 Tohoku Earthquake caused a devastating tsunami along the shoreline from to Kanto districts. Although many of tide gauge stations coast were saturated or damaged due tsunami, two cabled ocean-bottom sensors installed off Kamaishi successfully recorded waveform just above source rupture area. records indicated characteristic two-stage development sequence: smoothly increasing amplitude 0 2 m during first 800 s earthquake origin time, and short-period impulsive with peak more than 5 in...
[1] The 2011 Tohoku earthquake was observed by dense strong motion, teleseismic, geodetic, and tsunami networks. We first inverted each of the datasets obtained networks separately, for rupture process earthquake. then performed checkerboard resolution tests assessing resolving power these datasets. In order to overcome limited resolutions separate inversions differences in their results, we a quadruple joint inversion all data determine source model most suitable explaining model, maximum...
We show fine‐scale variations of seismic velocities and converted teleseismic waves that reveal the presence zones high‐pressure fluids released by progressive metamorphic dehydration reactions in subducting Philippine Sea plate Tokai district, Japan. These have a strong correlation with distribution slow earthquakes, including long‐term slip (LTSS) low‐frequency earthquakes (LFEs). Overpressured LTSS region appear to be trapped within oceanic crust an impermeable cap rock fore‐arc, impede...
We here show relocated hypocenters within a seismic sequence with normal faults in the northern part of Ibaraki Prefecture, triggered after M 9.0 2011 off Pacific coast Tohoku Earthquake. Depth-sections from center region to north an earthquake alignment dipping westwards at 40° 50° depths shallower than 10 km. On other hand, south cross-cutting geometry consisting conjugate westward- and eastward-dipping planes same depths. The dip angles hypocenter alignments are roughly consistent nodal...
Recently, the distributed acoustic sensing (DAS) measurement, which utilizes an optical fiber itself as a sensor, becomes popular for various fields and is being applied to seismic observations. The shortest spatial sampling of DAS observations reaches few meters, total measurement distance greater than 50 km. A high temporal rate achieved. Due these characteristics, allows dense observation linear array. Applying seafloor cable advantageous because quantity data can be significantly...
Tsunami heights greater than 4 m were observed at several coastal tide-gauge stations during the tsunami generated by 2011 off Pacific coast of Tohoku Earthquake (Mw 9.0), causing thousands casualties and damaging infrastructure along Japan. We retrospectively applied an algorithm near-field forecasting to data that recorded various offshore 5–10 min before reached nearest its source. inverted waveform estimate distribution initial sea-surface height, then waveforms synthesized from...
Abstract The tectonic stress field was investigated in and around the aftershock area of Hokkaido Eastern Iburi earthquake ( M JMA = 6.7) occurred on 6 September 2018. We deployed 26 temporary seismic stations for approximately 2 months located 1785 aftershocks precisely. Among these aftershocks, 894 focal mechanism solutions were determined using first-motion polarity P wave from observation permanent networks University, Japan Meteorological Agency (JMA), High Sensitivity Seismograph...
Abstract Seismic activity in the Noto region of Ishikawa Prefecture, central Japan, has increased since August 2020 and continued as 2023. Stress changes due to subsurface sources increases fluid pressure have been discussed causes seismic increase. In this study, S-wave polarization anisotropy was investigated by splitting analysis using temporary permanent stations located epicenter area. We also wave velocity structure source analyzing tomography. The fast orientations (fast shear...
The 2024 MW 7.5 Noto earthquake in Japan was preceded by an intense seismic swarm, likely driven upward fluid migration. Crustal velocities are influenced external perturbations from earthquakes, with the presence of pressurized fluids crust amplifying these induced velocity changes. Consequently, we characterize subsurface examining coseismic changes associated mainshock. We combined data permanent Hi-net and temporary stations. stations were deployed Tohoku University Earthquake Research...
Abstract The 2024 Noto-Hanto earthquake with a magnitude of 7.6 occurred in the Noto Peninsula on January 1, 2024. mainshock had reverse fault focal solution and direction compression axis was northwest–southeast. In Peninsula, swarms have been observed since December 2020. contrast to this swarm activity, extending marine area. Therefore, we performed rapid response seafloor seismic observation source region its vicinity. We deployed 34 free-fall pop-up type ocean bottom seismometers (OBSs)...
The velocity structure and accurate aftershock distributions of the 2004 mid‐Niigata prefecture earthquake are elucidated by inverting arrival times from 716 aftershocks using double‐difference tomography. Fourteen temporal seismic stations were immediately deployed in around source region within 46 h occurrence mainshock. velocities a hanging wall lower than those footwall, contrast extends to depth approximately 10 km. associated with mainshock distributed clear boundary between low high...
Large historical and recent intraplate earthquakes have been concentrated along a contractional zone at the eastern margin of Japan Sea back‐arc basin. Here we present high‐resolution three‐dimensional tomographic imaging seismic velocities in this using data from dense seismograph deployment. We discover that stepwise tilted block structures basement, which are geophysical evidence Miocene rift system, widely distributed beneath thick sedimentary Most aftershocks following align roughly...
Research Article| May 01, 2013 Seismic‐ and Tsunami‐Wave Propagation of the 2011 Off Pacific Coast Tohoku Earthquake as Inferred from Tsunami‐Coupled Finite‐Difference Simulation Takuto Maeda; Maeda Institute, The University Tokyo, 1‐1‐1 Yayoi, Bunkyo‐ku, Tokyo 113‐0032, Japanmaeda@eri.u-tokyo.ac.jp *Also at Center for Integrated Disaster Information Research, Interfaculty Initiative in Studies, Japan. Search other works by this author on: GSW Google Scholar Takashi Furumura; Furumura...
In the present study, we analyze seismic signals from a continuous volcanic tremor that occurred during small phreatic eruption of Hakone volcano, in Owakudani geothermal region central Japan, on June 29, 2015. The were detected for 2 days, 29 to July 1, at stations near vents. frequency component tremors showed broad peak within 1–6 Hz. characteristics did not vary with time and independent amplitude tremor. largest was observed end activity, days after onset eruption. We estimated location...
We deployed a dense temporal seismic network in the source region of 2004 mid‐Niigata prefecture earthquake (thrust fault), Japan. A detailed velocity structure and accurate aftershock distributions were elucidated by inverting arrival times using double‐difference tomography. stress tensor inversion first‐motion data was also conducted order to investigate field. The velocities hanging wall above main shock fault are lower than those footwall, with contrast extending depth approximately 10...
Strong ground motions from the 2011 off Pacific coast of Tohoku Earthquake, most powerful earthquake to have occurred in and around Japan after installation a modern seismic network, were recorded for more than 300 seconds by dense wide-span Metropolitan Seismic Observation Network (MeSO-net), installed Tokyo metropolitan area about 200 km away epicenter. We investigate rupture process space time performing semblance-enhanced stacking analysis waveforms frequency range 0.05 0.5 Hz. By...
Intense swarm‐like seismicity associated with shallow normal faulting was induced in Ibaraki and Fukushima prefectures, Japan, following the 2011 Tohoku‐Oki earthquake. This shows a systematic spatiotemporal evolution, but little is known of heterogeneity crustal structure this region, or its influence on evolution seismicity. Here, we elucidate high‐resolution model region determine precise hypocenter locations. Hypocenters Prefecture reveal planar earthquake alignment dipping SW at ~45°,...
We studied the seismicity rate increase in Kanto region around Tokyo following 2011 Tohoku-Oki earthquake (Mw 9.0) to examine whether this was correlated with static increases Coulomb failure function (ΔCFF) of sequence. Because earthquakes exhibit various focal mechanisms, receiver faults for ΔCFF were assumed be mechanism solutions nearly 19 000 that previously occurred. Our results showed number which had a positive (∼12 000) is much larger than those negative (∼2000). Comparison values...
Abstract We present a deep‐learning approach for earthquake detection using waveforms from seismic array consisting of multiple seismographs. Although automated, techniques have recently been developed at the single‐station level, they potential difficulty in reducing false detections owing to presence local noise inherent each station. Here, we propose deep‐learning‐based efficiently analyze observed by array, whereby employ convolutional neural networks conjunction with graph partitioning...
From June 26, 2000, an intensive earthquake swarm started under Miyake-jima Island, 180 km south off Japan. This was closely related to the eruption of probably dominated by underground magmatic activity. The spread toward northwestern ocean region from in which a huge number earthquakes (over 100, 000) including five large events M>6.0 were detected over about two months. most active since we seismic observations 1970's.Although there are some telemetered observation stations on Izu...