A5024473325- earthquake and tectonic studies
- High-pressure geophysics and materials
- Seismic Waves and Analysis
- Seismology and Earthquake Studies
- Earthquake Detection and Analysis
- Geological and Geochemical Analysis
- Geological and Geophysical Studies
- Methane Hydrates and Related Phenomena
- Seismic Imaging and Inversion Techniques
- Geophysical Methods and Applications
- Cancer, Hypoxia, and Metabolism
- Geophysical and Geoelectrical Methods
- Synthetic Aperture Radar (SAR) Applications and Techniques
- Geophysics and Gravity Measurements
- Advanced SAR Imaging Techniques
- Geological Studies and Exploration
- Astro and Planetary Science
- Seismic Performance and Analysis
- Hydrocarbon exploration and reservoir analysis
- Underwater Acoustics Research
- Statistical and numerical algorithms
- Ocean Waves and Remote Sensing
- Marine and environmental studies
- Earthquake and Disaster Impact Studies
- Atomic and Subatomic Physics Research
Okayama University of Science
2020-2021
Kyushu University
2015-2021
Institute of Seismology
2016-2020
Institute of Volcanology and Seismology
2016-2019
Japan Agency for Marine-Earth Science and Technology
2009-2015
Kyoto University
2001-2015
The University of Tokyo
2009-2011
Association for the Development of Earthquake Prediction
2009
Yale University
2004
The frequency dependence of Q in Earth's upper mantle is investigated using the continuous P wave spectra over 0.08 < f 8.0 Hz. Regional waveform data from 23 events Pacific slab recorded on broadband stations western Japan were used to create spectral ratio estimates waves which sample a subducting and wedge. We assumed power‐law model ( ) = 0 / α applied grid search determine best fit . inferred (0.2 0.4) most regions consistent with laboratory solid olivine but not partially molten...
We analyze seismic waveforms from deep‐focus earthquakes occurring in the subducting slab beneath Japan, recorded by broadband ocean bottom seismometers (BBOBSs) installed on northwestern Pacific Ocean seafloor. The data reveal with a low‐frequency direct P onset, followed large‐amplitude, high‐frequency, long‐duration Po and So waves. From analysis of BBOBS records numerical finite‐difference method simulation wave propagation, we elucidate generation propagation processes such guided...
Abstract We investigate seismic wave velocity structure and spatial distribution of the seismicity in source region 2016 Kumamoto earthquake sequence. A one‐dimensional mean shows that seismogenic zone has a high‐velocity low‐Vp/Vs ratio relative to average Kyushu Island. This indicates crust is relatively strong, capable sustaining sufficiently high strain energy facilitate two large ( M j > 6.5) earthquakes close proximity one another rapid succession. Three‐dimensional tomography...
Abstract Po / So waves are characterized by their high‐frequency content and long‐duration travel over great distances (up to 3000km) through the oceanic lithosphere. developed multiple forward scattering of P S due small‐scale stochastic random heterogeneities. To study nature these heterogeneities, analyzed in Philippine Sea Plate, which consists three regions with different lithospheric ages. In propagate youngest region (15 Ma) more effectively older regions. We investigate mechanism...
The M JMA 7.3 Kumamoto earthquake that occurred at 1:25 JST on April 16, 2016, not only triggered aftershocks in the vicinity of epicenter, but also earthquakes were 50–100 km away from epicenter main shock. active seismicity can be divided into three regions: (1) faults, (2) northern region Aso volcano (50 northeast mainshock epicenter), and (3) regions around volcanoes, Yufu, Tsurumi, Garan (100 epicenter). Notably, zones between these are distinctively seismically inactive. electric...
Abstract Crustal earthquake ruptures tend to initiate near fluid-rich zones. However, it is relatively unknown whether zones can further promote or arrest these ruptures. We image the electrical resistivity structure around focal area of 2016 Kumamoto sequence by using 200 sites broadband magnetotelluric data, and discuss its quantitative relationship initiation, growth, processes. The that initiated along outer edge low-resistivity (< 30 Ωm) tended become large earthquakes, whereas those...
Abstract For understanding the physical condition of earthquake generation, we estimated deviatoric stress fields and fault planes large earthquakes in hypocentral area 2016 Kumamoto sequence, central Kyushu, Japan. We analyzed precise hypocenters their focal mechanism tensors from 1993 to 2017 found complex largest foreshock mainshock during sequence. The faults could not be detected preceding high seismic activity mainshock. analyses obtained pre‐ post‐sequence moment tensor data revealed...
Abstract The attenuation of seismic wave energy is caused by intrinsic absorption and scattering. former involves the conversion to heat via internal friction due anelasticity medium, whereas latter scattering random elastic heterogeneities in medium. Quantifying both ( ) therefore important for understanding physical properties Earth's interior predicting propagation. Here we develop a new procedure separately map three‐dimensional (3‐D) structures. path‐averaged values are obtained an...
Seismic structure of the upper mantle transition zone beneath Philippine Sea region is studied using waveform modeling. Models AZ41 and AZ40 were derived to represent north central part northwestern regions, respectively. has high‐velocity anomalies from 510 km 660 3% faster than a global model ak135 , depression ‘660’ discontinuity 690 km, small (+2%) at km. Model same as except there no ‘660’. On other hand, waveforms which sampled southern can be explained with . These results support...
Seismic attenuation and traveltime anomalies in the vicinity of Izu‐Bonin subduction zone are inferred from waveform data recorded by Broadband Ocean Bottom Seismometers (BBOBSs) deployed as part Stagnant Slab Project. We measure path‐averaged P waves both S using 10 regional earthquakes within slab. The observed relation between is quantitatively evaluated on basis mineral physics. For that sample slab Pacific mantle beneath slab, consistent with predictions based thermal effect. wedge show...
Research Article| September 11, 2018 Numerical Shake Prediction for Earthquake Early Warning Incorporating Heterogeneous Attenuation Structure: The Case of the 2016 Kumamoto Masashi Ogiso; Ogiso aMeteorological Institute, Japan Meteorological Agency, 1‐1 Nagamine, Tsukuba, Ibaraki 305‐0052, Japan, mogiso@mri-jma.go.jpmhoshiba@mri-jma.go.jp Search other works by this author on: GSW Google Scholar Mitsuyuki Hoshiba; Hoshiba Azusa Shito; Shito bInstitute Seismology and Volcanology, Kyushu...
Subsurface structures may control the migration of magma beneath a volcano. We used high-resolution seismic tomography to image low- P-wave velocity (Vp) zone Unzen Volcano, Japan, at depths 3-16 km sea level. The top this low-Vp is located Mt. Fugendake volcano, which emitted 0.21 km3 dacitic as lava domes and pyroclastic flows during eruptions in 1990-1995. Based on hypocenter migrations prior 1990-1995 modeled pressure source locations for recorded crustal deformation, we conclude that...