Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1186/s40623-022-01606-5

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

We propose a new algorithm, focusing on spatial amplitude patterns, to automatically detect volcano seismic events from continuous waveforms. Candidate seismic events are detected based on signal-to-noise ratios. The algorithm then utilizes supervised machine learning to classify the existing candidate events into true and false categories. The input learning data are the ratios of the number of time samples with amplitudes greater than the background noise level at 1 s intervals (large amplitude ratios) given at every station site, and a manual classification table in which `true'' or `false'' flags are assigned to candidate events. A two-step approach is implemented in our procedure. First, using the large amplitude ratios at all stations, a neural network model representing a continuous spatial distribution of large amplitude probabilities is investigated at 1 s intervals. Second, several features are extracted from these spatial distributions, and a relation between the features and classification to true and false events is learned by a support vector machine. This two-step approach is essential to account for temporal loss of data, or station installation, movement, or removal. We evaluated the algorithm using data from Mt. Ontake, Japan, during the first ten days of a dense observation trial in the summit region (November 1–10, 2017). Results showed a classification accuracy of more than 97 per cent.

DOI： 10.1093/gji/ggaa593

Other Link： https://nagoya.repo.nii.ac.jp/records/2001674

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2020JB020249

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/gji/ggaa519

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.4294/zisin.2019-11

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2019JB018156

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Very-long-period (VLP) seismic events at Asama volcano in central Japan are characterized by a transient signal of 10-20 s duration. Associated with the transient motion, a high-frequency (HF) oscillation within the 5-10 Hz band is observed. We investigated the location and size of the oscillation source in the HF band (HF source) using an amplitude source location method and compared our results with those for the VLP band (VLP source) deduced in our previous waveform inversion study. We analysed 1437 VLP events recorded during an intense observation campaign during 2008-2009, and additional 571 events surrounding an eruptive activity in 2015 (including a VLP event that immediately preceded an eruption). The HF source locations of most events were deeper than the VLP source locations by ~150 m, although there was almost no time lag between the signals. This suggests a strong connection between the two sources, with one source immediately responding to the other. The eruptive VLP event had an HF source location close to normal VLP events but had a greater event size. We surmise that the HF signal is caused by an inflow of volcanic gas from depth into a semi-vertical crack-like cavity (as imaged in our previous waveform inversion study), and the VLP signal is caused by resultant inflation of the same cavity. The centroid of inflation (VLP source) is near the roof of the cavity, where gas accumulates, whereas the HF oscillation is emitted more intensely from lower and narrower portions of the cavity. This results in source depth differences between the two signal bands. In this model, the inflation rate of the cavity is controlled by the volume flux of the gas inflow, producing similar temporal variations between the VLP and HF signals. According to this model, the eruptive VLP is associated with a greater amount of gas inflow and accumulation, which likely played a key role in the eruption.

DOI： 10.1093/gji/ggz021

Other Link： https://nagoya.repo.nii.ac.jp/records/28498

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2018JB015557

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1029/2018JB015866

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/2017GL074593

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/2016GL071929

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Although phreatic eruptions are common volcanic phenomena that sometimes result in significant disasters, their dynamics are poorly understood. In this study, we address the dynamics of the phreatic eruption of Mount Ontake, Japan, in 2014 based on analyses of a tilt change observed immediately (450 s) before the eruption onset. We conducted two sets of analysis: a waveform inversion and a modified phase-space analysis. Our waveform inversion of the tilt signal points to a vertical tensile crack at a depth of 1100 m. Our modified phase-space analysis suggests that the tilt change was at first a linear function in time that then switched to exponential growth. We constructed simple analytical models to explain these temporal functions. The linear function was explained by the boiling of underground water controlled by a constant heat supply from a greater depth. The exponential function was explained by the decompression-induced boiling of water and the upward Darcy flow of the water vapor through a permeable region of small cracks that were newly created in response to ongoing boiling. We interpret that this region was intact prior to the start of the tilt change, and thus, it has acted as a permeability barrier for the upward migration of fluids; it was a breakage of this barrier that led to the eruption.

DOI： 10.1002/2016JB013739

Other Link： https://nagoya.repo.nii.ac.jp/records/24369

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Although a model of the resonance of a rectangular fluid-filled crack (crack model) is one of the most frequently used source models of long-period seismic events at volcanoes, there has been no analytical solution for the resonance frequencies. We previously proposed an empirical expression for the resonance frequencies as a mathematical function of the crack length, aperture, and properties of the fluid and the surrounding elastic medium. However, the expression contained an empirical constant that had to be investigated numerically for each crack aspect ratio and oscillation mode, a requirement that prevented widespread use of the expression. In the present study, we examined the theoretical basis for the expression. We assumed that the ratio of the crack wall displacement to the fluid pressure near each crack edge varied as the square root of the distance from the edge. Using this assumption, we showed theoretically that the previously proposed empirical analytical expression was a good approximation (difference <=2 per cent) to another more complete expression. This theoretical expression is a closed form of a mathematical function of the crack model parameters and oscillation mode number; there are no empirical constants to be determined numerically. The expression thus enabled us to analytically compute the resonance frequencies for arbitrary rectangular cracks, and the results were in good agreement (difference <=5 per cent) with numerical solutions. Resonance frequencies of cracks can be very easily predicted using this expression. This predictive ability may enhance our quantitative understanding of the processes that generate long-period events at volcanoes.

DOI： 10.1093/gji/ggx019

Other Link： https://nagoya.repo.nii.ac.jp/records/24370

Authorship：Lead author,　Corresponding author   Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/ncomms10797

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

The phreatic eruption of Mt. Ontake in 2014 was preceded for 25 s by a very long period (VLP) seismic event recorded at one broadband and three short-period seismic stations located within 5000 m of the summit. We performed waveform inversion of the event within a frequency band of 0.1-0.5 Hz that pointed to an ENE-WSW opening (NNW-SSE striking) subvertical tensile crack at a depth of 300-1000 m beneath the region of the eruptive vents. This crack orientation is consistent with alignments of volcano-tectonic (VT) earthquake hypocenters and eruptive vents as well as normal faulting (E-W tension) focal mechanisms of the VT earthquakes. We interpreted these results as follows: the VLP source crack was one of a group of preexisting faults that was opened immediately before the eruption because of the passage of ascending gas from depth to the surface.

DOI： 10.1186/s40623-015-0358-0

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1186/s40623-015-0349-1

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1186/s40623-015-0288-x

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Temporal variations of Green functions associated with the eruptive activity at Sakurajima Volcano, Japan, were estimated using an accurately controlled routinely operated signal system (ACROSS). We deconvolved 400 s waveforms of the ACROSS signal at nearby stations by a known source time function and stacked the results based on the time relative to individual eruptions and the eruption intervals; the quantities obtained by this procedure are Green functions corresponding to various stages of the eruptive activity. We found an energy decrease in the later phase of the Green functions in active eruptive periods. This energy decrease, localized in the 2-6 s window of the Green functions, is difficult to explain by contamination from volcanic earthquakes and tremors. The decrease could be more reasonably attributed to a subsurface structure change caused by the volcanic activity.

DOI： 10.1002/2015GL064351

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.epsl.2015.02.034

Language：English   Publishing type：Research paper (scientific journal)  

A network of 10 satellite-telemetered broadband stations was established under a cooperative project between Japan and the Philippines, and a source analysis system based on waveform inversion of regional seismograms was adapted to operationalize a regional moment tensor analysis of Philippine earthquakes. This study presents the source information generated by the system for recent damaging earthquakes: the Mw6.7 Negros and Mw7.6 offshore Samar in 2012, and the Mw7.2 in Bohol in 2013. Results show that the Negros event was generated by shallow NE-SW thrust faulting with a small strike-slip component, and that the centroid was located slightly offshore. The Samar event occurred in relation to an outer-trench thrust fault within the Philippine Sea Plate, adjacent to a part of the Philippine Trench that has relatively low seismicity. Our centroid moment tensor (CMT) solutions show that the Samar event triggered distinct clusters of outer-rise normal and thrust aftershocks, which we explain as being consistent with a Coulomb stress change in the area. Finally, we infer that the previously unidentified fault zone that generated the Bohol earthquake has a length of ~ 100 km, is oriented ENE-WSW, transects parts of Bohol, and extends offshore towards Cebu. These examples show how recent improvements in Philippine earthquake monitoring could contribute to the characterization of earthquake sources and in the understanding of the seismotectonics of the area.

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

During a phreatic explosion at Mayon Volcano, Philippines, on 7 May 2013, a very long period seismic event with a peak frequency of 0.4 Hz was observed. Our frequency-domain waveform inversion solution of the event in the frequency range 0.1-0.6 Hz is consistent with a subhorizontal tensile crack and a vertical single force at a shallow location beneath the summit crater. The source time functions obtained by the waveform inversion are band-passed forms. We estimated the deconvolved forms of the source time functions (DSTFs), which are source time functions corrected for the effects of the band-pass filter. The DSTF of the crack can be approximated by an impulse-type function composed of inflation followed by deflation, whereas the DSTF of the single force can be approximated by a downward impulse. The inflation of the crack may be attributed to boiling of underground water and its deflation can be attributed to discharge of water vapor, whereas the downward force may be understood as the counterforce of the explosion. Our results suggest that only a portion of the crack wall was destroyed by the explosion. We could not find clear precursors in seismic, thermography, geothermal, geodetic, and meteorological data. We present a model of repeated explosions in which an explosion can occur once the fragmented portion of the crack is sealed by precipitation of clay minerals or hydrothermal secondary deposits. This model may explain the absence of clear precursory signals before the 2013 explosion.

DOI： 10.1002/2014JB011440

Language：English   Publishing type：Research paper (scientific journal)  

Taal Volcano, Philippines, is one of the world's most dangerous volcanoes given its history of explosive eruptions and its close proximity to populated areas. A real-time broadband seismic network was recently deployed and has detected volcano-tectonic events beneath Taal. Our source location analysis of these volcano-tectonic events, using onset arrival times and high-frequency seismic amplitudes, points to the existence of a region of strong attenuation near the ground surface beneath the east flank of Volcano Island in Taal Lake. This region is beneath the active fumarolic area and above sources of pressure contributing inflation and deflation, and it coincides with a region of high electrical conductivity. The high-attenuation region matches that inferred from an active-seismic survey conducted at Taal in 1993. These features strongly suggest that the high-attenuation region represents an actively degassing magma body near the surface that has existed for more than 20 years.

DOI： 10.1002/2014GL061193

Language：English   Publishing type：Research paper (scientific journal)  

A spherical source, one of the simplest seismic sources, has been represented in various ways in the literature. These representations include a spherical source with outward radial expansion (S1), a spherical crack source with outward and inward crack wall motions along the spherical surface (S2), an isotropic source represented by three mutually perpendicular vector dipoles (S3) or three mutually perpendicular tensile cracks (S4), and a spherical source undergoing a transformational expansion (S5). We systematically examined these sources and their static displacement fields to clarify how these representations are mutually related. We also considered the sources in a bimaterial medium, in which the source material is different from the surrounding medium, as a model of a magma or hydrothermal reservoir. Our examinations show that the source volume change of a spherical source (S1) (actual volume) can be uniquely determined from the seismic moment of an isotropic source (S3) regardless of our assumption of the source medium and that the actual volume of S1 is related to the seismic moment of S3 through the equivalence of the displacement fields due to these two sources. The seismic moment of S3 is also related through another equation to the source volume change of three tensile cracks (S4), which is equal to the source volume changes defined in S2 and S5. This relation has different forms, depending on the source medium and source process. This study provides a unified view for quantifying a spherical source using the seismic moment of an isotropic source determined from waveform inversion analysis.

DOI： 10.1186/1880-5981-66-7

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

The fluid-filled crack model has been widely used to interpret the peak frequencies of long-period (LP) seismic events at volcanoes. Up to now, numerical methods have been used to compute resonant frequencies in the model. We propose a simple analytical formula for the longitudinal resonance frequencies of a fluid-filled crack. We evaluated the formula by comparing its results with the resonant frequencies computed by finite difference method code. The comparison revealed that the formula well describes the resonant frequencies of both 2-D and 3-D cracks. The formula enables simple and rapid estimates of the fluid properties and geometries of LP source cracks.

DOI： 10.1002/grl.51002

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

We analyzed observations of a swarm of more than 40,000 long-period (LP) seismic events at Taal volcano, Philippines, in 2010-2011. The event waveforms are strongly correlated to each other, consistent with a fixed source location, and begin with a dilatational first motion. They have a peak frequency around 0.8 Hz and a quality factor Q of 6. Waveform inversion of the events pointed to a tensile crack source dipping 30^o-60^o at a shallow (100-200 m) depth. A simulation using a fluid-filled crack model indicated that the complex frequencies of the waveforms are explained by the fundamental longitudinal mode resonance of a vapor-filled crack 188 m long. A satellite thermal infrared image acquired during the swarm period suggests that the LP events were not accompanied by surface gas releases. We considered a vapor transportation model in which vapor exsolved from magma and rose in a fissure extending to the LP source. This model yielded estimates that 10⁵-10⁷ m³ of magma was involved in the LP swarm and that the temperature of vapor in the LP source crack was around 600 K. We modeled a triggering mechanism of the crack resonance based on sudden condensation of vapor at the crack tip in a cold aquifer. This model explained observed characteristics of the events including the dilatational first motion, the total volumetric change, and the fixed source location.

DOI： 10.1002/jgrb.50205

Language：English   Publishing type：Research paper (scientific journal)  

The amplitude source location (ASL) method, which uses high-frequency amplitudes under the assumption of isotropic S-wave radiation, has been shown to be useful for locating the sources of various types of volcano-seismic signals. We tested the ASL method by using synthetic seismograms and examined the source amplitudes determined by this method for various types of volcano-seismic signals observed at different volcanoes. Our synthetic tests indicated that, although ASL results are not strongly influenced by velocity structure and noise, they do depend on site amplification factors at individual stations. We first applied the ASL method to volcano-tectonic (VT) earthquakes at Taal volcano, Philippines. Our ASL results for the largest VT earthquake showed that a frequency range of 7 -12 Hz and a Q value of 50 were appropriate for the source location determination. Using these values, we systematically estimated source locations and amplitudes of VT earthquakes at Taal. We next applied the ASL method to long-period events at Cotopaxi volcano and to explosions at Tungurahua volcano in Ecuador. We proposed a practical approach to minimize the effects of site amplifications among different volcano seismic networks, and compared the source amplitudes of these various volcano-seismic events with their seismic magnitudes. We found a proportional relation between seismic magnitude and the logarithm of the source amplitude. The ASL method can be used to determine source locations of small events for which onset measurements are difficult, and thus can estimate the sizes of events over a wider range of sizes compared with conventional hypocenter determination approaches. Previously, there has been no parameter widely used to quantify the sources of volcano-seismic signals. This study showed that the source amplitude determined by the ASL method may be a useful quantitative measure of volcano-seismic event size.

DOI： 10.1016/j.jvolgeores.2013.03.002

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

We examined the effects of water domains on seismic wavefields at the Taal volcano, Philippines, where there is a summit crater lake on an active volcanic island surrounded by a caldera lake. We conducted forward waveform simulation and synthetic waveform inversion using the 3D finite-difference method for various models with and without the water lakes. Our study demonstrated the existence of both near- and far-field effects of the water domains. The near-field effect is related to source excitation affected by a water domain, and the far-field effect is caused by dispersion of Rayleigh waves propagating through a water domain. Our study also showed that the replacement of water by a vacuum rather than by a solid medium provides a better approximation of a water domain. A water domain has considerable effect on seismic waveforms and must be properly treated when the waveform period is shorter than 2 s, even if recording stations lie in the near field. If the waveform period is longer than 5 s, a water domain has a minor effect on seismic waveforms and may be replaced by a vacuum.

DOI： 10.5047/eps.2012.07.004

Language：English   Publishing type：Research paper (scientific journal)  

Multiple volcanic observations conducted at Mt. Asama, Japan, provide evidence of a link between single very-long-period (VLP) seismic pulses and volcanic gas emissions. SO₂ flux measurements were conducted on 2 June 2009, when Mt. Asama was producing ash-free eruptions with VLP pulses. Gas bursts from a vent at the crater bottom following the VLP pulses provided an excellent opportunity to examine the relation directly. The SO₂ emission for each eruption was calculated by integrating high temporal SO₂ flux data obtained by the SO₂ imaging system and subtracting the contribution from quiescent degassing from fumaroles around the crater bottom. A seismic moment of VLP pulse was estimated by the waveform inversion. We observed seven eruptions and obtained the proportional relation between VLP pulse moment and SO₂ emission. The relation determined is consistent with the VLP source model; these observational results are the first report of a quantitative comparison between single VLP pulse moment and volcanic gas emission.

DOI： 10.1029/2011GL047555

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

We observed seismic events consisting of several one-sided velocity pulses with durations of 5-30 s (hereafter called very-long-period or VLP pulses) using up to 14 broad-band seismometers installed near the summit area of Asama volcano, Japan. Particle motions do not point to a single source location despite their rectilinearities, suggesting a non-isotropic source mechanism, together with path effect. We conducted moment-tensor inversion analyses for these events using the Green's functions of not only translational motions but also of tilt motions. The best-fitting source locations are located north of the crater centre, at depths of 100-150 m below the crater bottom. The principal value ratios of moment-tensor solutions can be approximated as 5:3:2, which is indicative of a combination of a tensile crack and a cylinder, with the strike and dip angle of the crack both being nearly 70^o, and symmetry axis of the cylinder being inclined by nearly 30^o from the vertical. The time histories of moment-tensors are indicative of an initial sudden pressurization and subsequent gradual depressurization at the source region. We sought to model VLP pulses at Asama volcano by considering the inflow and outflow of gas at the source cavity, compensated by boiling in another deeper reservoir.

DOI： 10.1111/j.1365-246X.2011.04938.x

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

A new waveform inversion method is proposed to deal with horizontal seismograms strongly contaminated by tilt signals, without assumptions regarding tilt motions. Instead of decomposing the horizontal seismograms into translational and tilt contributions, we realize this task by calculating the Green's functions consisting of not only the seismometer's response to the synthetic translational motions but also to the synthetic tilt motions. A finite difference method (FDM), which uses a staggered grid and a perfect matched layer (PML) boundary condition, is used to calculate the Green's functions. This method enables calculation of wavefields which have wavelengths of up to 10 times larger than the dimension of the computational grid. Although reflected waves from the numerical boundaries are negligible, comparisons with analytical solutions evidence errors of up to several per cent. These occur either because the source-to-receiver distance is small once compared to the grid size, or as a consequence of the half-cell difference between the actual free surface and the station location. In addition, in the case that the free surface is not flat, an error of up to 60 per cent occurs in calculating the tilt motion, due to the stair-like approximation of topography in the FDM. This latter error can be reduced to 10 per cent by averaging the tilts at five adjacent cells aligned in the direction of the tilt component, centred on the target grid cell. By applying this algorithm, a waveform inversion can be used to successfully reconstruct the vertical and horizontal seismograms of very-long-period (10-30 s) pulses at Asama Volcano, central Japan, despite the fact that the horizontal seismograms are strongly contaminated by tilt signals.

DOI： 10.1111/j.1365-246X.2010.04892.x

Language：Japanese   Publishing type：Research paper (scientific journal)  

Event date： 2024.5

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Venue：幕張   Country：Japan  

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Event date： 2017.5

Language：Japanese   Presentation type：Poster presentation  

Country：Japan  

Event date： 2017.5

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.5

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.5

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.5

Language：Japanese   Presentation type：Poster presentation  

Country：Japan  

Event date： 2016.12

Language：English   Presentation type：Oral presentation (general)  

Venue：San Francisco   Country：United States  

Event date： 2016.12

Language：English   Presentation type：Poster presentation  

Venue：San Francisco   Country：United States  

Event date： 2016.12

Language：English   Presentation type：Poster presentation  

Venue：San Francisco   Country：United States  

Event date： 2016.12

Language：English   Presentation type：Poster presentation  

Venue：San Francisco   Country：United States  

Event date： 2016.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富士吉田   Country：Japan  

Event date： 2016.10

Language：Japanese   Presentation type：Poster presentation  

Venue：富士吉田   Country：Japan  

Event date： 2016.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2016.10

Language：Japanese   Presentation type：Poster presentation  

Venue：名古屋   Country：Japan  

Event date： 2016.10

Language：Japanese   Presentation type：Poster presentation  

Venue：名古屋   Country：Japan  

Event date： 2016.10

Language：Japanese   Presentation type：Poster presentation  

Venue：名古屋   Country：Japan  

Event date： 2016.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2016.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2016.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2016.5

Language：Japanese   Presentation type：Poster presentation  

Venue：幕張   Country：Japan  

Event date： 2016.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2016.5

Language：Japanese   Presentation type：Poster presentation  

Venue：幕張   Country：Japan  

Event date： 2016.5

Language：Japanese   Presentation type：Poster presentation  

Venue：幕張   Country：Japan  

Event date： 2016.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2015.12

Language：English   Presentation type：Oral presentation (invited, special)  

Country：United States  

Event date： 2015.12

Language：English   Presentation type：Oral presentation (general)  

Country：United States  

Event date： 2015.12

Language：English   Presentation type：Oral presentation (general)  

Country：United States  

Event date： 2015.12

Language：English   Presentation type：Poster presentation  

Country：United States  

Event date： 2015.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2015.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Poster presentation  

Venue：富山   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山   Country：Japan  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：富山   Country：Japan  

Event date： 2015.6 - 2015.7

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2015.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2015.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2015.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2015.5

Language：Japanese   Presentation type：Poster presentation  

Venue：幕張   Country：Japan  

Event date： 2015.5

Language：Japanese   Presentation type：Poster presentation  

Venue：幕張   Country：Japan  

Event date： 2014.12

Language：English   Presentation type：Poster presentation  

Country：United States  

Event date： 2014.12

Language：English   Presentation type：Poster presentation  

Country：United States  

Event date： 2014.11

Language：English   Presentation type：Oral presentation (general)  

Country：Philippines  

Event date： 2014.11

Language：English   Presentation type：Poster presentation  

Country：Philippines  

Event date： 2014.11

Language：English   Presentation type：Oral presentation (general)  

Country：Philippines  

Event date： 2014.11

Language：English   Presentation type：Oral presentation (general)  

Country：Philippines  

Event date： 2014.11

Language：Japanese   Presentation type：Poster presentation  

Country：Japan  

Event date： 2014.11

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2014.4 - 2014.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：横浜   Country：Japan  

Event date： 2014.4 - 2014.5

Language：Japanese   Presentation type：Poster presentation  

Venue：横浜   Country：Japan  

Event date： 2014.4 - 2014.5

Language：Japanese   Presentation type：Poster presentation  

Venue：横浜   Country：Japan  

Event date： 2013.12

Language：English   Presentation type：Poster presentation  

Country：United States  

Event date： 2013.12

Language：English   Presentation type：Oral presentation (general)  

Country：United States  

Event date： 2013.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：横浜   Country：Japan  

Event date： 2013.7

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2013.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2013.7

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2013.7

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2013.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2013.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2012.12

Language：English   Presentation type：Poster presentation  

Country：United States  

Event date： 2012.12

Language：English   Presentation type：Poster presentation  

Country：United States  

Event date： 2012.10

Language：Japanese   Presentation type：Poster presentation  

Venue：御代田   Country：Japan  

Event date： 2012.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：御代田   Country：Japan  

Event date： 2012.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2012.5

Language：Japanese   Presentation type：Poster presentation  

Venue：幕張   Country：Japan  

Event date： 2011.12

Language：English   Presentation type：Poster presentation  

Country：United States  

Event date： 2011.10

Language：Japanese   Presentation type：Poster presentation  

Venue：旭川   Country：Japan  

Event date： 2011.6 - 2011.7

Language：English   Presentation type：Poster presentation  

Country：Australia  

Event date： 2011.5

Language：Japanese   Presentation type：Poster presentation  

Venue：幕張   Country：Japan  

Event date： 2011.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2010.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都   Country：Japan  

Event date： 2010.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan  

Event date： 2010.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京大学地震研究所   Country：Japan  

Event date： 2009.12

Language：English   Presentation type：Poster presentation  

Venue：San Francisco   Country：United States  

Event date： 2009.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：小田原   Country：Japan  

Event date： 2009.5

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2009.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：幕張   Country：Japan