Teleseismic P-Wave Attenuation Beneath the Arabian Plate
Talal Merghelani; Jun Kawahara; Kaoru Miyashita; Hani Zahran
Geosciences, 09 Nov. 2023, [Reviewed]

Spatio‑temporal characteristics of frictional properties on the subducting Pacific Plate off the east of Tohoku district, Japan estimated from stress drops of small earthquakes
Takuji Yamada; Meitong Duan; Jun Kawahara, The east coast of the Tohoku district, Japan has a high seismicity, including aftershocks of the 2011 M9 Tohoku earthquake. We analyzed 1142 earthquakes with $$4.4 \le M_{W} \le 5.0$$

4.4
≤

M
W

≤
5.0

that occurred in 2003 through 2018 and obtained spatio-temporal pattern of stress drop on the Pacific Plate that subducts beneath the Okhotsk Plate. Here we show that small earthquakes at edges of a region with a large slip during the 2011 Tohoku earthquake had high values of stress drop, indicating that the areas had a high frictional strength and suppressed the coseismic slip of the 2011 Tohoku earthquake. In addition, stress drops of small earthquakes in some of the areas likely decreased after the 2011 Tohoku earthquake. This indicates that the frictional strength decreased at the areas due to the following aftershocks of the 2011 Tohoku earthquake, consistent with a high aftershock activity. This also supports that the frictional properties on a subducting plate interface can be monitored by stress drops of small earthquakes, as pointed out by some previous studies., Springer Science and Business Media LLC
Earth, Planets and Space, 18 Jan. 2021, [Reviewed]

Spatial pattern in stress drops of moderate-sized earthquakes on the Pacific Plate off the south-east of Hokkaido, Japan: implications for the heterogeneity of frictional properties
Takuji Yamada; Yu Saito; Yuichiro Tanioka; Jun Kawahara, We show that the spatial heterogeneity in the coseismic displacement of large earthquakes likely reflects the spatial characteristics of the frictional properties and that it can be inferred from the stress drop of moderate-sized earthquakes. We analyzed stress drops of 686 earthquakes with magnitudes of 4.0 to 5.0 off the south-east of Hokkaido, Japan, and investigated the spatial heterogeneity between the difference of shear strength and dynamic stress level on the Pacific Plate. We deconvolved observed P and S waves with those of collocated small earthquakes and derived the source effect of the earthquakes. We then estimated the corner frequencies of the earthquakes and calculated stress drops using a circular fault model. The values of stress drops showed a spatial pattern consistent with slip distributions of historical large earthquakes. Earthquakes that occurred in the area with a large coseismic slip during the 1968 Tokachi-oki (M (W) 8.2) and the 2003 Tokachi-oki (M (W) 8.0) earthquakes had large values of stress drop, whereas earthquakes in the afterslip area of the 2003 Tokachi-oki earthquake showed smaller values. In addition, an area between coseismic ruptures of the 1973 Nemuro-oki (M (W) 7.8) and the 2003 Tokachi-oki earthquakes had a large value of stress drop. Ruptures occurred in this area during the 1952 Tokachi-oki earthquake (M (W) 8.1), and the area acted as a barrier during the 2003 Tokachi-oki earthquake. These facts suggest that the frictional properties of the plate interface show little temporal change, and their spatial pattern can be monitored by stress drops of moderate-sized earthquakes. The spatial heterogeneity provides important information for estimating the slip pattern of a future large earthquake and discussing a policy for disaster mitigation, especially for regions in which slip patterns of historical large earthquakes are unclear., SPRINGEROPEN
PROGRESS IN EARTH AND PLANETARY SCIENCE, Dec. 2017, [Reviewed]

Estimation of the 3-D velocity structure of the Sorachi-Yezo and Oshima Belts in the western part of Hokkaido, Japan
Ismail Husain Fathi; Kaoru Miyashita; Jun Kawahara, We adopted the seismic tomography technique to refine the three-dimensional velocity structure model of the western part of Hokkaido, Japan. Using the P-wave first arrival data listed by Japan Meteorological Agency from 2002 to 2005, we could estimate a 3-D inhomogeneous velocity structure model with a low velocity at a depth of 14 km beneath Asahikawa. The crustal structure near Sapporo was characterized by lateral velocity change toward the southern seaside. The low-velocity zone near Urakawa, proposed by previous research, was also clarified. In general, the present model showed lower-velocity values for most of the crustal layers in the area concerned. The results of this study were affected by less number of higher magnitude events (M ≥ 0.5) in the central part of the area of interest. However, the perturbation results for comparatively shallow layers (6-50 km) were good in resolution. It was found that the source region of the Rumoi-Nanbu earthquake of December 14, 2004 was characterized by a low-velocity zone, located between high velocity zones. Such an inhomogeneous crustal structure might play an important role in the relatively high seismic activity in the Rumoi-Nanbu earthquake source region. © 2012 Saudi Society for Geosciences.
Arabian Journal of Geosciences, Aug. 2013, [Reviewed]

P wave attenuation structure beneath the Kanto district and surrounding area, Japan
Talal Merghelani; Jun Kawahara; Kaoru Miyashita, Spectral ratios of teleseismic P waves for 15 deep (> 200 km) earthquakes recorded at 146 High-Sensitivity Seismographic Network stations in the Kanto district and its surrounding area, eastern Japan, were inverted for attenuation parameter . The dataset consisted of good-quality vertical-component seismograms, whose P phases were handpicked. The P wave spectral ratios with high signal-to-noise ratios were calculated up to 1 Hz for all the station pairs, linear regressed, and then inverted for using the technique of least squares . The result showed that the active volcanic areas were clearly characterized by high . In contrast, varied in the nonvolcanic areas. The present result on the distribution was roughly consistent with the shallow part (< 30 km) of an attenuation structure, which has been previously obtained based on 3-D tomography by using records of high-frequency (around 5 Hz) P waves from local earthquakes. This suggested that the present method of estimation is valid. The advantage and possible application to other areas were also discussed., SPRINGER HEIDELBERG
ARABIAN JOURNAL OF GEOSCIENCES, Jun. 2013, [Reviewed]

Simulations of P-SV wave scattering due to cracks by the 2-D finite difference method
Yuji Suzuki; Takahiro Shiina; Jun Kawahara; Taro Okamoto; Kaoru Miyashita, We simulate P-SV wave scattering by 2-D parallel cracks using the finite difference method (FDM). Here, special emphasis is put on simplicity
we apply a standard FDM (second-order velocity-stress scheme with a staggered grid) to media including traction-free, infinitesimally thin cracks, which are expressed in a simple manner. As an accuracy test of the present method, we calculate the displacement discontinuity along an isolated crack caused by harmonic waves using the method, which is compared with the corresponding results based on a reliable boundary integral equation method. The test resultantly indicates that the present method yields sufficient accuracy. As an application of this method, we also simulate wave propagation in media with randomly distributed cracks. We experimentally determine the attenuation and velocity dispersion induced by scattering from the synthetic seismograms, using a waveform averaging technique. It is shown that the results are well explained by a theory based on the Foldy approximation, if the crack density is sufficiently low. The theory appears valid with a crack density up to at least 0.1 for SV wave incidence, whereas the validity limit appears lower for P wave incidence. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS)., Springer Berlin
Earth, Planets and Space, 2013, [Reviewed]

Retrieval of long-wave tsunami Green's function from the cross-correlation of continuous ocean waves excited by far-field random noise sources on the basis of a first-order Born approximation
Tatsuhiko Saito; Jun Kawahara, We investigate the theoretical background for the retrieval of the tsunami Green's function from the cross-correlation of continuous ocean waves. Considering that a tsunami is a long-wavelength ocean wave described by 2-D linear long-wave equations, and that the sea-bottom topography acts as a set of point-like scatterers, we use a first-order Born approximation in deriving the tsunami Green's function having coda waves. The scattering pattern is non-isotropic and symmetrical with respect to the forward and backward directions. We indicate a retrieval process which shows that the derivative of the cross-correlation function of wavefields at two receivers with respect to the lag time gives the tsunami Green's function when point noise sources generating continuous ocean waves are distributed far from, and surrounding, the two receivers. Note that this relation between the cross-correlation and the Green's function is different from the case in which uncorrelated plane-wave incidence from all directions is assumed to be continuous ocean waves. The Green's function retrieved from continuous ocean waves will be used as a reference to examine the validity of the Green's function obtained by numerical simulations., TERRA SCIENTIFIC PUBL CO
EARTH PLANETS AND SPACE, 2012, [Reviewed]

Retrieval of tsunami Green’s function from continuous records of sea level changes　　　　　　　　　　　　　　　
Jun Kawahara; Tatsuhiko Saito; Kyoko Momiyama; Kaoru Miyashita, Lead
Proceedings of Workshop on Recent developments in seismic wave scattering and heterogeneities in the Earth, Oct. 2011

Scattering attenuation of elastic waves due to low-contrast inclusions
Jun Kawahara, Seismic scattering attenuation due to random lithospheric heterogeneity has been theoretically modeled using two approaches. One approach is the Born approximation theory (BAT), which is primarily used to treat weak continuous heterogeneity, and the other approach is the Foldy approximation theory (FAT), which deals with sparsely distributed discrete inclusions. We apply the BAT to elastic wave scattering due to inclusions having low contrast with the matrix, and compare the results with those predicted by the FAT. We thus investigate the valid wavenumber range of the BAT based on a reasonable assumption that the inclusions are distributed so sparsely that the FAT is effectively correct for any wavenumber. For simplicity, we consider a specific type of round inclusion, which is either two- or three-dimensional and has a two-valued wave velocity and/or mass density. Both theories are confirmed to yield essentially equivalent results below a certain wavenumber limit, depending on the contrast. This is known as the Rayleigh-Gans scattering regime. Beyond the wavenumber limit, the BAT overestimates the attenuation for common-mode scattering due to wave-velocity contrast, but remains valid with respect to the attenuation for scattering due to mass-density contrast and/or conversion scattering. These conclusions are independent of the spatial dimensions of the media as well as the modes of the elastic waves (P or S). Some advantages of the BAT over the FAT for application to low-contrast inclusions are discussed. (C) 2010 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
WAVE MOTION, Apr. 2011, [Reviewed]

Attenuation and dispersion of antiplane shear waves due to scattering by many two-dimensional cavities
Jun Kawahara; Taichi Ohno; Kiyoshi Yomogida, Propagation and scattering of antiplane shear waves within media with two-dimensional cavities are numerically simulated, and the attenuation and phase velocities are experimentally determined. The results are compared with the predictions by the Foldy theory and its three corrected versions. If the cavity concentrations are small such as 0.02, the differences among the theoretical predictions are insignificant, and every theory is consistent with the experimental results. For higher concentrations such as 0.1, the differences become significant, but there are no objective grounds to say that any of the corrected versions of the Foldy theory works better than the original. If the error tolerance is as high as 10%, the simple Foldy formula may remain useful for concentrations up to about 0.1. (C) 2009 Acoustical Society of America. [DOI: 10.1121/1.3124779], ACOUSTICAL SOC AMER AMER INST PHYSICS
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, Jun. 2009, [Reviewed]

1998 dense seismic refraction/wide-angle experiment in the eastern flank of the Ou backbone range, Northern Honshu, Japan
The Research Group for Explosion Seismology, In 1997 and 1998, intensive wide-angle seismic experiments were carried out in the northern part of Honshu Island, Japan to clarify various scale crustal deformation ongoing in the northern Hon-shu arc. The 1998 experiment was intended to reveal the crustal scale structural heterogeneity west of the western boundary fault of the Kitakami Lowland. In a 20km×50km area, 236 receivers were deployed to record 13 dynamite shots detonated on August 10. On September 3, M 6.1 event oc-curred in the vicinity of our study area. To investigate seismic velocity change associated with the event, another experiment was undertaken on November 8 using an additional dynamite source at the same place of the northernmost shot point in the August experiment. The data qualities of these two experiments are good, and first arrivals can be traced in almost the entire part of the experi-mental area. They show significant travel time change across the western boundary fault of the Kitakami Lowland. In the NS profile, a remarkable later phase is recognized, which is interpreted as a wide-angle reflection from midcrustal interface at a depth of 6－7km. This paper presents the outline of the experiments and fundamental data obtained., 東京大学地震研究所
Bulletin of the Earthquake Research Institute, University of Tokyo, 23 Jun. 2008, [Reviewed]

Deep seismic refraction/wide-angle reflection profiling in Central Japan
The Research Group for Seismic Expedition in Central Japan, An extensive onshore-offshore seismic refraction/wide-angle reflection experiment was undertaken in 2001. The profile line was extended from the eastern part of the Nankai trough to Central Japan. The land profile line of 261-km length was laid from the Tokai district to the coastal region of the Sea of Japan, crossing an expected fault area of the forthcoming Tokai earthquake, an aseismic slip region north of the fault area, the Median Tectonic Line and the Niigata-Kobe Tectonic line. On this profile, 391 receivers were deployed to observe 6 dynamite shots with 100－500kg charge. Data obtained are of good quality, from which clear first arrivals are traced beyond 120－160km offsets. The most important feature in these data is strong reflection from the subducted Philippine Sea plate observed in the southernmost part of the profile. This paper presents the outline of this seismic expedition and fundamental data obtained., 東京大学地震研究所
Bulletin of the Earthquake Research Institute, University of Tokyo, 23 Jun. 2008, [Reviewed]

Seismic expedition in the Hinagu fault area, Kyushu Island, Japan
The Research Group for the 2003 Hinagu Fault Seismic Expedition, The Hinagu fault system, Kyushu, Japan, is located in the westernmost part of the Beppu-Shimabara graben. This fault system is characterized by a quite high seismic activity and estimated to have a higher seismic risk among active faults in Kyushu Island. In 2003, we conducted an extensive seismic expedition in and around the Hinagu fault area. This expedition involves seismic refraction/wide-angle reflection experiment using dynamite shots and seismic array observation both for the active and passive seismic sources. For the refraction/wide-angle reflection study, two profile lines of 56.4 and 32.1km lengths were set in EW and NNE-SSW directions, respectively, on which 7 dynamite shots of 100－200kg charge and 359 recorders were deployed. The array observations, which were designed for high-resolution imaging of crustal scatterors and reflectors, were undertaken at 5 sites in the fault region. This paper presents the outline of this seismic expedition and fundamental data obtained., 東京大学地震研究所
Bulletin of the Earthquake Research Institute, University of Tokyo, 23 Jun. 2008, [Reviewed]

Simulations of SH wave scattering due to cracks by the 2-D finite difference method
Y Suzuki; J Kawahara; T Okamoto; K Miyashita, We simulate SH wave scattering by 2-D parallel cracks using the finite difference method (FDM), instead of the popularly used boundary integral equation method (BIEM). Here special emphasis is put on simplicity; we apply a standard FDM (fourth-order velocity-stress scheme with a staggered grid) to media including traction-free cracks, which are expressed by arrays of grid points with zero traction. Two types of accuracy tests based on comparison with a reliable BIEM, suggest that the present method gives practically sufficient accuracy, except for the wavefields in the vicinity of cracks, which can be well handled if the second-order FDM is used instead. As an application of this method, we also simulate wave propagation in media with randomly distributed cracks of the same length. We experimentally determine the attenuation and velocity dispersion induced by scattering from the synthetic seismograms, using a waveform averaging technique. It is shown that the results are well explained by a theory based on the Foldy approximation for crack densities of up to about 0.1. The presence of a free surface does not affect the validity of the theory. A preliminary experiment also suggests that the validity will not change even for multi-scale cracks., TERRA SCIENTIFIC PUBL CO
EARTH PLANETS AND SPACE, 2006, [Reviewed]

Characteristics of secular crustal deformation in the Kanto and Tokai regions, deduced from the wavelet analysis of GPS time-series data, and their tectonic implications
Kaoru Miyashita; Jianxin Li; Kathamana Vijaykumar; Jun Kawahara, 日本測地学会
測地学会誌, 25 Jun. 2005, [Reviewed]

SH wave envelopes in 2-D media with discrete scatterers: Theories vs. wave simulations　　　　　　　　　　　　　　　
Jun Kawahara; Kiyoshi Yomogida, Lead
Proceedings of Workshop on Probing Earth Media Having Small-Scale Heterogeneities, Nov. 2004

SH wave envelopes in 2-D media with discrete scatterers　　　　　　　　　　　　　　　
Jun Kawahara; Kiyoshi Yomogida, Lead
Proceedings of the 1st International Workshop on Active Monitoring in the Solid Earth Geophysics, Jun. 2004

Seismic refraction / wide-angle refection experiment across the Hidaka collision zone, Hokkaido : Ohtaki-Urahoro profile
Research Group For Explosion Seismology, The Hidaka region, central Hokkaido, Japan is characterized as an arc-arc collision zone between the Kuril forearc and the Northeast Japan arc. In 1999, an intensive seismic refraction/ wide-angle reflection experiment was carried out across the Hidaka region to investigate crustal deformation associated with the collision process. We deployed 297 stations on an EW profile line of 227-km to record 6 dynamite shots of 100～700kg charges. Remarkable travel time jumps observed in the western part of the profile indicate a velocity reversal beneath the foreland area of the collision zone. In the eastern part of the profile, travel time curves obtained show a severe undulation. Very clear later phases observed in this part strongly indicate the existence of mid-crustal reflectors within the colliding Kuril forearc., The University of Tokyo
Bulletin of the Earthquake Research Institute, University of Tokyo, 27 Dec. 2002, [Reviewed]

Seismic refraction / wide-angle reflection experiment across the foreland area of the Hidaka collision zone, Hokkaido, Japan : Ohtaki-Biratori profile
Research Group For Explosion Seismology, The University of Tokyo
Bulletin of the Earthquake Research Institute, University of Tokyo, 27 Dec. 2002, [Reviewed]

Cutoff scattering angles for random acoustic media
J Kawahara, [1] The seismic scattering attenuation in randomly inhomogeneous media is successfully explained by a Born approximation-based theory, established by R. S. Wu and H. Sato. The key is to eliminate the contribution of forward scattering within a cutoff scattering angle (CSA) when evaluating the scattering attenuation in order to avoid overestimating attenuation at high frequencies. The value of the CSA is, however, not objectively determined in the theory, and the choice of it remains an open question. We investigate the constraint by causality on the choice of the CSA for random acoustic media with constant densities. On the basis of the Kramers-Kronig relation, we derive simple relations of the phase velocities in the high- and low-frequency limits with the CSA. We further discuss the probable values of the CSA on the basis of a thought experiment. Surprisingly, they are independent of the details of inhomogeneities., AMER GEOPHYSICAL UNION
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Jan. 2002, [Reviewed]

Wave-Theoretical Properties of Cracked Media
Jun Kawahara, 日本地震学会
Zisin, Second Series, Jun. 2001, [Reviewed]

Seismic refraction/wide-angle experiment across the Northern Honshu arc
Research Group For Explosion Seismology, An intensive wide-angle seismic experiment was carried out in the northern part of Honshu Island, Japan in October 1997. This experiment was carried out as an important component of a multi-diciplinary project aiming at elucidating the physical process of crustal evolution and deformation of the Northern Honshu Arc. We deployed 293 stations on an EW profile line of 150-km length to record 10 onshore and two offshore shots. Travel time curves obtained show a severe undulation in the western part of the profile, probably reflecting the crustal heterogeneity associated with the major fault systems developing on both sides of the backbone range. Rather clear later arrivals are recognized in the eastern part of the profile under the Kitakami Mountains., The University of Tokyo
Bulletin of the Earthquake Research Institute, University of Tokyo, 29 Oct. 1999, [Reviewed]

Explosion seismic observations in Eastern Kyushu, Japan, II. : Ajimu-Tano profile
Research Group For Explosion Seismology, A seismic refraction survey was conducted along a profile from Ajimu, Oita Prefecture, to Tano, Miyazaki Prefecture, on November 14, 1996. This profile is almost the same as the profile of the survey conducted in 1994. The total length of the Ajimu-Tano Profile was about 230km, and three shots and 236 temporary observation sites were arranged along the profile. Charge size of all shots was 500kg. Record signals of the observation sites in a distance range of less than 120km were of good quality. Travel times of first arrivals indicated the complex velocity structure of the shallow part of the crust. Reflected waves from the deeper part of the crust or the upper mantle were also clearly observed. Analysis of the high-quality data sets obtained in the 1996 and 1994 experiments might reveal a fine image of the crust in this area., The University of Tokyo
Bulletin of the Earthquake Research Institute, University of Tokyo, 29 Oct. 1999, [Reviewed]

Effects of wave propagation in random media on seismic explorations : Studies based on numerical simulations
Jun Kawahara, 物理探査学会
Butsuri-Tansa, 1999, [Reviewed]

Seismic scattering by cracks containing liquids
Jun Kawahara, The Society of Exploration Geophysicists of Japan
Proceeding of the 4th SEGJ International Symposium - Fracture Imaging -, Dec. 1998, [Reviewed]

Numerical simulations of seismic wave propagation in random media
Jun Kawahara
Zisin, Second Series, May 1997, [Reviewed]

Comment on "Crustal anisotropy from local observations of shear-wave splitting in West Bohemia, Czech Republic" by Vaclav Vavrycuk
Jun Kawahara, SEISMOLOGICAL SOC AMER
Bulletin of the Seismological Society of America, 01 Apr. 1995, [Reviewed]

Multiple scattering of SH waves in 2‐D elastic media with distributed cracks
Yoshio Murai; Jun Kawahara; Teruo Yamashita, We compute synthetic seismograms of SH waves that are multiply scattered by randomly distributed cracks. All the cracks are assumed to have the same length and strike direction
the crack surfaces are assumed to be stress‐free, or to undergo viscous friction. We analyse the deterministic wave equation, and rigorously treat multiple crack interactions. We first calculate the wavefield in the wavenumber domain, and then we obtain the time‐domain solution by its Fourier transform. A plane wave whose time dependence is described by the Ricker wavelet is assumed to be incident upon the region of crack distribution. The scattered waves are efficiently excited when the half‐wavelength of the incident wave is close to or shorter than the crack length. High‐wavenumber components are shown to be more abundant in the scattered waves when the crack distribution is denser. The time delay of the arrival of the primary wave, due to crack scattering, is shown to be prominent when the wavelength of the incident wave is much longer than the crack length. When the crack surfaces are subject to viscous friction, both the amplitudes of the scattered waves and the time delay of the primary‐wave arrivals are smaller than those for the case of stress‐free crack surfaces. When the crack distribution is statistically homogeneous, the calculated attenuation coefficient Q−1 and phase velocity v of the primary wave are generally consistent with those obtained by a stochastic analysis based on Foldy's approximation. A short analysis on the effect of inhomogeneous crack distribution shows that the wavenumber at which Q−1 is at its peak value is smaller than that expected from the stochastic analysis for homogeneous crack distribution. Copyright © 1995, Wiley Blackwell. All rights reserved
Geophysical Journal International, 1995, [Reviewed]

SCATTERING OF ELASTIC-WAVES BY A FRACTURE-ZONE CONTAINING RANDOMLY DISTRIBUTED CRACKS
J KAWAHARA; T YAMASHITA, We theoretically study the scattering of P, SV and SH waves by a zonal distribution of cracks, which simulates a fault fracture zone. An investigation is conducted how the geometrical properties of the crack distribution and the frictional characteristics of the crack surface are reflected in the attenuation and dispersion of incident waves, as well as in the amplitudes of the transmitted and reflected waves from the zone. If the crack distribution within the fault zone changes temporally during the preparation process of the expected earthquake, it will be important for earthquake prediction to monitor it, utilizing the scattering-induced wave phenomena.
We consider the two-dimensional problem. Aligned cracks with the same length are assumed to be randomly distributed in a zone with a finite width, on which elastic waves are assumed to be incident. The distribution of cracks is assumed to be homogeneous and sparse. The crack surface is assumed to be stress-free, or to undergo viscous friction; the latter case simulates fluid-filled cracks. The opening displacement of the crack is assumed to be negligibly small. The idea of the mean wave formalism is employed in the analysis, and Foldy's approximation is assumed.
When the crack surface is stress-free, it is commonly observed for every wave mode (P, SV and SH) that the attenuation coefficient Q-1 peaks around ka approximately 1, the phase velocity is almost independent of k in the range ka < 1 and it increases monotonically with k in the range ka > 1, where k is the intrinsic S wavenumber and a is the half length of the crack. The effect of the friction is to shift the peak of Q-1 and the comer of the phase velocity curve to the low wavenumber range. The high wavenumber asymptote of Q-1 is proportional to k-1 independently of model parameters and the wave modes. If the seismological observation that Q-1 of S waves has a peak at around 0.5 Hz in the earth's crust is combined with our results, the upper limit of crack size within the crust is estimated about 4 km. The information regarding the transmitted and reflected waves, such as the high wavenumber limit of the amplitude of the transmitted wave etc., allows estimation of the strength of the friction., BIRKHAUSER VERLAG AG
PURE AND APPLIED GEOPHYSICS, 1992, [Reviewed]

SCATTERING OF P, SV-WAVES BY RANDOM DISTRIBUTION OF ALIGNED OPEN CRACKS
J KAWAHARA, CENTER ACADEMIC PUBL JAPAN
JOURNAL OF PHYSICS OF THE EARTH, 1992, [Reviewed]

弱い離散的不均質による弾性波の散乱減衰
河原 純
月刊地球, 01 Apr. 2007

Effect of depth-dependent scattering coefficients on the seismic envelopes　　　　　　　　　　　　　　　
Masaki Koizumi; Jun Kawahara
The Seismological Society of Japan 2024 Fall Meeting, 22 Oct. 2024
20241021, 20241023

Numerical simulations of guided waves propagating in subducting oceanic crust (2)　　　　　　　　　　　　　　　
Jun Kawahara; Kazuki Kidoguchi; Takahiro Shiina
The Seismological Society of Japan 2022 Fall Meeting, 24 Oct. 2022

Numerical simulations of guided waves propagating in subducting oceanic crust　　　　　　　　　　　　　　　
Kazuki Kidoguchi; Jun Kawahara; Takahiro Shiina
The Seismological Society of Japan 2021 Fall Meeting, 15 Oct. 2021

Numerical simulations of weak localization of scalar waves based on the finite difference method (2)　　　　　　　　　　　　　　　
Jun Kawahara; Masanobu Sato
Japan Geoscience Union Meeting 2021, 05 Jun. 2021

Propagation characteristics of two-dimensional scalar waves in alternating layered structures　　　　　　　　　　　　　　　
Kazuki Kidoguchi; Jun Kawahara
JpGU - AGU Joint Meeting 2020: Virtual, 12 Jul. 2020

Near-field tsunami forecast based on MT/CMT data for the Pacific coast of eastern Japan　　　　　　　　　　　　　　　
Akihiro Toyoda; Jun Kawahara; Tatsuhiko Saito
The Seismological Society of Japan 2019 Fall Meeting, 17 Sep. 2019

Numerical simulations of weak localization of scalar waves based on the finite difference method　　　　　　　　　　　　　　　
Masanobu Sato; Jun Kawahara
The Seismological Society of Japan 2019 Fall Meeting, 16 Sep. 2019

Site amplification factors for KiK-net stations in and around Ibaraki Prefecture estimated by the coda normalization method　　　　　　　　　　　　　　　
Jun Kawahara; Takahiro Nakamura; Takuji Yamada
Japan Geoscience Union Meeting 2019, 27 May 2019

Comparison of the stress change due to slow slip events and the seismicity in the Bungo channel area during 2002-2004　　　　　　　　　　　　　　　
Kei Minegishi1; Jun Kawahara; Kei Katsumata
Japan Geoscience Union Meeting 2018, 24 May 2018

Envelopes of scalar plane wavelets propagating through 2-D random media with power-law spectra　　　　　　　　　　　　　　　
Yuji Tomiyama; Jun Kawahara; Kentaro Emoto
Joint Scientific Assembly of the International Association of Geodesy and International Association of Seismology and Physics of the Earth’s Interior, 01 Aug. 2017

Envelopes of scalar plane wavelets propagating through 2-D random media,with power-law spectra　　　　　　　　　　　　　　　
Yuji Tomiyama; Jun Kawahara; Kentaro Emoto
Joint Scientific Assembly of the International Association of Geodesy and International Association of Seismology and Physics of the Earth’s Interior, 01 Aug. 2017

Estimation of scattering coefficient and intrinsic absorption in the Chugoku district (2)　　　　　　　　　　　　　　　
Daisuke Takahagi; Jun Kawahara; Kentaro Emoto; Tatsuhiko Saito
JpGU-AGU Joint Meeting 2017, 24 May 2017, Japan Geoscience Union, American Geophysical Union

Estimation of scattering coefficient and intrinsic absorption in the Chugoku district　　　　　　　　　　　　　　　
Yuto Sasaki; Jun Kawahara; Tatsuhiko Saito; Kentaro Emoto
The Seismological Society of Japan 2015 Fall Meeting, 27 Oct. 2015

Modeling inclined cracks in a 2 -D finite difference grid: the case of P-SV wave scattering　　　　　　　　　　　　　　　
Takakazu Yanaka; Jun Kawahara; Takahiro Shiina; Taro Okamoto
The Seismological Society of Japan 2015 Fall Meeting, 27 Oct. 2015

On estimation of scattering coefficient and intrinsic absorption from spatial distribution of seismic energy (3)　　　　　　　　　　　　　　　
Yuto Sasaki; Jun Kawahara; Tatsuhiko Saito; Kentaro Emoto
Japan Geoscience Union Meeting 2015, 26 May 2015

On estimation of scattering coefficient and intrinsic absorption from spatial distribution of seismic energy (2)　　　　　　　　　　　　　　　
Kiyoshiro Saito; Jun Kawahara; Tatsuhiko Saito; Kentaro Emoto
The Seismological Society of Japan 2014 Fall Meeting, 26 Nov. 2014

SH wave scattering due to viscous fluid filled cracks: Application of 2D finite difference simulation　　　　　　　　　　　　　　　
Takahiro Shiina; Jun Kawahara; Taro Okamoto
The Seismological Society of Japan 2014 Fall Meeting, 26 Nov. 2014

Modeling inclined cracks in a 2-D finite difference grid　　　　　　　　　　　　　　　
Arata Nasuno; Jun Kawahara; Takahiro Shiina; Taro Okamoto
Japan Geoscience Union Meeting 2014, 29 Apr. 2014

On estimation of scattering coefficient and intrinsic absorption from spatial distribution of seismic energy　　　　　　　　　　　　　　　
Kiyoshiro Saito; Jun Kawahara; Tatsuhiko Saito
The Seismological Society of Japan 2013 Fall Meeting, 09 Oct. 2013

Comparison of seismic interferometry and cepstrum analysis in inferring seismic basement structures　　　　　　　　　　　　　　　
Hiromu Ishikuma; Jun Kawahara; Kaoru Miyashita; Naoshi Hirata; Shinichi Sakai
The Seismological Society of Japan 2012 Fall Meeting, 18 Oct. 2012

Monte Carlo simulation of seismogram envelopes including the effect of energy trap by scatterers　　　　　　　　　　　　　　　
Kiyoshiro Saito; Jun Kawahara
The Seismological Society of Japan 2012 Fall Meeting, 18 Oct. 2012

Retrieval of tsunami Green’s function from continuous records of sea level changes　　　　　　　　　　　　　　　
J. Kawahara; T. Saito; K. Momiyama; K. Miyashita
Workshop on “Recent developments in seismic wave scattering and heterogeneities in the Earth”, 28 Oct. 2011

粘性流体を含む亀裂によるSH波散乱の2次元差分法シミュレーション　　　　　　　　　　　　　　　
椎名高裕; 河原純; 岡元太郎
日本地震学会2011年度秋季大会, 13 Oct. 2011

室戸岬沖～初島沖間の海面水位変動の相互相関　　　　　　　　　　　　　　　
籾山京子; 河原純; 齊藤竜彦; 宮下芳
日本地球惑星科学連合2011年大会, 22 May 2011

Spatial Variations of P wave t* in the Kanto and southern Tohoku regions　　　　　　　　　　　　　　　
メルガラニ タラル; 河原 純; 宮下 芳
日本地球惑星科学連合2010年大会, 27 May 2010

介在物分布を含む2次元媒質中のSH波エンベロープ：マルコフ近似理論と数値実験の比較　　　　　　　　　　　　　　　
河原純; 齊藤竜彦; 蓬田清
日本地震学会2009年度秋季大会, 23 Oct. 2009

介在物分布を含む2次元媒質中のSHコーダ波エンベロープ　　　　　　　　　　　　　　　
河原純; 蓬田清
日本地球惑星科学連合2009年大会, 17 May 2009

Attenuation and Dispersion of SH Waves due to Scattering by Inclusions　　　　　　　　　　　　　　　
Jun Kawahara; Kiyoshi Yomogida
7th General Assembly of Asian Seismological Commission and Seismological Society of Japan, 2008 Fall meeting, 26 Nov. 2008

弱い離散的不均質による弾性波の散乱減衰(2)　　　　　　　　　　　　　　　
河原純
日本地球惑星科学連合2008年大会, 25 May 2008

Scattering Attenuation Due to Weak Discrete Inhomogeneities: Comparison of the Born and Foldy Approximations　　　　　　　　　　　　　　　
J. Kawahara
2009 American Geophysical Union Fall Meeting, 14 Dec. 2007

弱い離散的不均質による弾性波の散乱減衰　　　　　　　　　　　　　　　
河原純
日本地球惑星科学連合2007年大会, 21 May 2007

GPS年周地殻変動の地球潮汐仮説　　　　　　　　　　　　　　　
杉本善教; 宮下芳; 河原純
日本地球惑星科学連合2006年大会, 17 May 2006

弱い離散的不均質による散乱減衰に関するBorn近似解とFoldy近似解の等価性　　　　　　　　　　　　　　　
河原純
日本地球惑星科学連合2006年大会, 16 May 2006

断層破砕帯におけるトラップ波発生の数値シミュレーション　　　　　　　　　　　　　　　
後藤暢哉; 河原純; 村井芳夫; 宮下芳
日本地球惑星科学連合2006年大会, 16 May 2006

Modeling of SH wave envelopes in media with many cavities: Wave simulations vs. radiative transfer theory　　　　　　　　　　　　　　　
J. Kawahara; K. Yomogida
2004 American Geophysical Union Fall Meeting, 14 Dec. 2004

空隙群を含む2次元媒質中のSHコーダ波エンベロープ(3) ─輻射伝達理論との比較─　　　　　　　　　　　　　　　
河原純; 蓬田清
日本地震学会2004年度秋季大会, 11 Oct. 2004

SH wave envelopes in 2-D media with discrete scatterers: Theories vs. wave simulations　　　　　　　　　　　　　　　
J. Kawahara; K. Yomogida
Workshop on "Probing Earth Media Having Small-Scale Heterogeneities", 22 Jul. 2004

SH wave envelopes in 2-D media with discrete scatterers　　　　　　　　　　　　　　　
J. Kawahara; K. Yomogida
1st International Workshop on ,"Active Monitoring in the Solid Earth Geophysics", 02 Jul. 2004

Modeling of SH wave envelopes in media with many cavities　　　　　　　　　　　　　　　
J. Kawahara; K. Yomogida
2003 American Geophysical Union Fall Meeting, 08 Dec. 2003

Modeling of SH coda wave envelopes in 2-D media with cavities　　　　　　　　　　　　　　　
J. Kawahara; K. Yomogida
One-Day Satellite Workshop of IUGG 2003 "Seismic Waves in the Heterogeneous Earth: More Applications to Seismology and Exploration Geophysics", 10 Jul. 2003

Attenuation and dispersion of SH waves due to scattering by cavities　　　　　　　　　　　　　　　
J. Kawahara; T. Ohno; K. Yomogida
XXIII General Assembly of the International Union of Geodesy and Geophysics, 01 Jul. 2003

空隙群を含む2次元媒質中のSHコーダ波エンベロープ　　　　　　　　　　　　　　　
河原純; 蓬田清
日本地球惑星科学関連学会2003年合同大会, 26 May 2003

2次元差分法を用いた亀裂群によるSH波散乱のシミュレーション　　　　　　　　　　　　　　　
鈴木佑治; 河原純; 岡元太郎
日本地球惑星科学関連学会2003年合同大会, 26 May 2003

ランダムに配向した2次元亀裂群によるSH波の散乱のシミュレーション　　　　　　　　　　　　　　　
吉田智昭; 河原純; 村井芳夫
日本地球惑星科学関連学会2003年合同大会, 26 May 2003