A5014282416- earthquake and tectonic studies
- Earthquake Detection and Analysis
- Seismology and Earthquake Studies
- Seismic Waves and Analysis
- Geological and Geophysical Studies
- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Seismic Imaging and Inversion Techniques
- Geophysics and Gravity Measurements
- Methane Hydrates and Related Phenomena
- Geology and Paleoclimatology Research
- Geophysics and Sensor Technology
- Earthquake and Tsunami Effects
- GNSS positioning and interference
- Planetary Science and Exploration
- Geological and Tectonic Studies in Latin America
- Ionosphere and magnetosphere dynamics
- Oceanographic and Atmospheric Processes
- Distributed and Parallel Computing Systems
- Tropical and Extratropical Cyclones Research
- Meteorological Phenomena and Simulations
- Underwater Acoustics Research
- Geomagnetism and Paleomagnetism Studies
- Advanced Fiber Optic Sensors
- Scientific Computing and Data Management
The University of Tokyo
2015-2024
Association for the Development of Earthquake Prediction
2015-2024
Earthquake Engineering Research Institute
2002-2023
National Research Institute for Earth Science and Disaster Resilience
2022
California Institute of Technology
1993
The 15 January 2022 climactic eruption of Hunga volcano, Tonga, produced an explosion in the atmosphere a size that has not been documented modern geophysical record. event generated broad range atmospheric waves observed globally by various ground-based and spaceborne instrumentation networks. Most prominent was surface-guided Lamb wave (≲0.01 hertz), which we propagating for four (plus three antipodal) passages around Earth over 6 days. As measured amplitudes, comparable to 1883 Krakatau...
The recent tsunamigenic earthquake in Tohoku (11 March 2011) strongly affirms, one more time after the Sumatra event (26 December 2004), necessity to open new paradigms oceanic monitoring. Detection of ionospheric anomalies following tsunami demonstrated that ionosphere is sensitive propagation. Observations supported by modeling proved are deterministic and reproducible numerical via ocean/neutral‐atmosphere/ionosphere coupling mechanism. In essence, induces internal gravity waves...
We report seismic evidence for the transportation of water into deep mantle in subduction zone beneath northeastern Japan. Our data indicate that is released from hydrated oceanic crust at shallow depths (< ∼100 kilometers) and then forms a channel material on top subducting plate pathway mantle. result provides direct shows how transported ocean to cold environment.
Abstract Systematic tsunami traveltime delays of up to 15 min relative the numerically simulated long waves from 2010 Chilean and 2011 Tohoku‐Oki earthquakes were widely observed at deep ocean tsunamimeters. Enigmatic small negative phases appearing before main peak commonly found only trans‐oceanic locations. The frequency dependence measured phase velocities shows reverse dispersions periods, i.e., speed becomes slower periods beyond 1000 s. This is consistent with a mode coupled...
Abstract We applied a new method to compute tsunami Green's functions for slip inversion of the 1 April 2014 Iquique earthquake using both near‐field and far‐field waveforms. Inclusion effects elastic loading seafloor, compressibility seawater, geopotential variation in computed reproduced traveltime delay relative long‐wave simulation allowed us use records waveform inversion. Multiple time window was waveforms iteratively until result resembles stable moment rate function from teleseismic...
Abstract On 8 October 2023, mysterious tsunamis with a maximum wave height of 60 cm were observed in Izu Islands and southwestern Japan, although only seismic events body‐wave magnitudes m b 4–5 have been documented to the west Sofugan volcano. To investigate source process, we analyze tsunami waveforms recorded by an array network ocean bottom pressure gauges. Stacked gauge records suggest recurrent arrivals multiple trains. Deconvolution stacked from earlier event revealed over 10 that...
Long‐period harmonic Rayleigh waves were observed on seismometers during the 1991 Mt. Pinatubo eruption in Philippines. The amplitude spectrum of shows two distinct peaks at periods about 230 and 270 s. In Earth's atmosphere, long‐wavelength standing acoustic are bounded a low‐sound‐velocity channel between thermosphere ground. fundamental first overtone atmospheric trapped channels have approximately same horizontal wavelength frequency s, respectively, i.e., atmosphere solid earth satisfy...
Abstract The slip distribution of the 1960 Chile earthquake was estimated using geodetic data, local tsunami and newly usable transoceanic data. large slips triggered a significant which recorded by tide gauges around Pacific Ocean. We performed two‐step inversion to estimate distribution. In first step, we jointly inverted waveforms data recover ground seafloor vertical displacement. could not be used for waveform inversions until wave phase arrival time discrepancies were recently...
Abstract The main cause of tsunamis is large subduction zone earthquakes with seismic magnitudes M w > 7, but submarine volcanic processes can also generate tsunamis. At the Sumisu caldera in Izu–Bonin arc, moderate‐sized < 6 occur almost once a decade and meter‐scale source mechanism poorly understood. Here we use tsunami data from recent 2015 event to show that abrupt uplift caldera, brittle rupture ring fault system due overpressure its magma reservoir, caused earthquake tsunami....
Abstract Two submarine earthquakes ( M w 5.8) occurred near volcanic islands, Curtis and Cheeseman, in the Kermadec Arc 2009 2017. Following both earthquakes, similar tsunamis with wave heights of about a meter, larger than expected from their moderate seismic magnitudes, were observed by coastal tide gauges. We investigate source mechanism for analyzing tsunami data 2017 event. Tsunami waveform analysis indicates that earthquake uplifted submerged caldera around islands. Combined suggests...
Clear atmospheric pressure changes associated with the 2003 Tokachi‐Oki, Japan, earthquake Mw 8.3 were recorded microbarographs distributed in Japan. The change starts at arrival of seismic waves and reaches its maximum amplitude Rayleigh waves, suggesting that observed was driven by ground motion passing site. We computed seismic‐to‐pressure transfer function (i.e., spectral ratio to vertical velocity) for periods between 10 50 s from co‐located barograph seismograph records. Comparison...
Tsunami speed variations in the deep ocean caused by seawater density stratification is investigated using a newly developed propagator matrix method that applicable to with depth‐variable sound speeds and gradients. For 4 km ocean, total tsunami reduction 0.44% compared incompressible homogeneous seawater; two thirds of due elastic energy stored water one third mainly hydrostatic compression. are computed for global profiles, characteristic structures discussed. reductions proportional...
[1] Atmospheric pressure changes caused by the 2011 Off Pacific Coast of Tohoku, Japan earthquake (Mw = 9.0) are investigated. Sensitive microbarographs in and around recorded unequivocal signals associated with tsunami. We identify them as atmospheric boundary waves excited uplift subsidence ocean surface, on basis waveform characteristics well similarity data from ocean-bottom gauges. Potential usefulness an observation network is discussed regarding improvement tsunami warning system.
Abstract We inverted the 2010 Maule earthquake tsunami waveforms recorded at DART (Deep‐ocean Assessment and Reporting Tsunamis) stations in Pacific Ocean by taking into account effects of seawater compressibility, elasticity solid Earth, gravitational potential change. These slow down speed consequently move slip offshore or updip direction, consistent with distribution obtained a joint inversion DART, tide gauge, GPS, coastal geodetic data. Separate inversions only near‐field data...
Abstract Moderate earthquakes ( M w > 5) with moment tensors (MTs) dominated by a vertical compensated‐linear‐vector‐dipole (vertical‐CLVD) component are often generated dip slip along curved ring‐fault system at active volcanoes. However, relating their MTs to parameters has been proved difficult. The objective of this study is find robust way estimating some based on MT solutions obtained from long‐period seismic records. We first model the idealized ring‐faulting and show that...
Anomalously large tsunamis generated by a submarine volcanic earthquake were recorded an ocean bottom pressure gauge array.
Abstract Systemic travel time delays of up to 15 min relative the linear long waves for transoceanic tsunamis have been reported. A phase correction method, which converts into dispersive waves, was previously proposed consider seawater compressibility, elasticity Earth, and gravitational potential change associated with tsunami motion. In present study, we improved this method by incorporating effects ocean density stratification, actual raypath, bathymetry. The considered amounted...
Abstract Motivated by the unwarned tsunami disaster caused flank collapse of Anak Krakatau volcano on 22 December 2018, we used a landslide model to explore potential observing and warning systems for region. With estimated volume 0.24 km 3 relatively short duration (~3 5 min), volcanic edifice in southwest sector triggered higher than 40 m vicinity. The tsunami, however, attenuated rapidly as it propagated away from generation area, resulting lower 2 wave heights at tide gauges around Sunda...
Abstract The explosive 2022 Tonga submarine volcanic eruption produced a globally propagated atmospheric disturbance. A leading Lamb wave pulse was recorded as pressure worldwide. weather‐station network in Japan the together with temperature and wind conditions during passage of pulse. Individual records indicate little simultaneous change. However, after alignment at time arrivals stacking, clear changes synchronized change are evident. Assuming propagation, synthesized from record show...
Abstract Abundant high-quality distant tsunami records from the 2010 Maule (Chile) and 2011 Tohoku-Oki earthquakes have revealed two distinctive features compared to long-wave simulations. The show that traveltime delay of increases with distance earthquakes, initial phase reversal tsunamis appears grows systematically. conventional theory cannot explain observed waveforms traveltimes tsunamis, leading need for a new synthesize tsunamis. propagating elevated sea surface compresses seawater...
Energy flow and radiation of linearized acoustic–gravity waves propagation boundary in a gravitationally stratified isothermal compressible inviscid semi-infinite fluid from time-varying bottom are investigated the frequency–wavenumber domain. Impedance Z , ratio vertical displacement to pressure above it, is function frequency horizontal wavenumber (ω, k ) undulation. The amplitude phase at divide coordinates into wave-type regimes. In contrast pure acoustic or gravity wave case, continuous...
Abstract We apply a genetic algorithm to find the optimized unit sources using dispersive tsunami synthetics estimate source of 2012 Haida Gwaii earthquake. The optimal number and distribution gives sea surface elevation similar that from our previous slip on fault data, but different seismic data. difference is possibly due submarine mass failure in region. Dispersion effects during propagation reduce maximum amplitudes by up 20% conventional linear longwave model. also increase travel time...