Detection of Localized Small-Scale Heterogeneities in the Hanshin-Awaji Region, Japan, by Anomalous Amplification of Coda Level

Tsuruga, Kayoko

doi:10.1785/0120000002

Cited by 4 publications

(4 citation statements)

References 25 publications

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“…He also found an area of weak scattering correlated with a seismic gap in the Hokuriku region. Tsuruga et al (2003) estimated the spatial distribution of small-scale heterogeneities in and around the Hanshin-Awaji region, including the coseismic fault region of the 1995 Hyogo-ken Nanbu earthquakes by a method similar to this study. They found strong heterogeneities with a scale of 0.2-1.4 km located around the depth of 10 km along the Nojima fault.…”

Section: Spatial Distribution Of Heterogeneities In the Hidaka Regionmentioning

confidence: 99%

Characteristics of Small-Scale Heterogeneities in the Hidaka, Japan, Region Estimated by Coda Envelope Level

Taira¹

2003

Bulletin of the Seismological Society of America

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We estimated the spatial distribution of small-scale heterogeneities as anomalous amplification of coda level in the Hidaka, Japan, region. We analyzed 2768 seismograms in a frequency range of 1-32 Hz for 24 earthquakes recorded at 62 stations. First, we estimated the site effect of each station, using the coda normalization method with regional earthquake data of large epicentral distances. All the data processing was done after the correction of this site effect. Next, we determined coda amplitude factor (CAF), that is, the amplitude ratio of coda waves on each source-station pair relative to the averaged coda amplitude over stations, for earthquakes inside the region. We found systematic spatial variations of CAF, implying the existence of localized heterogeneities. At frequencies lower than 2 Hz, the CAF is relatively large in the west of the Hidaka Mountains, implying the possibility of strong heterogeneities with a scale of 0.6-1.3 km there. In a high-frequency range (Ͼ16 Hz), CAF values are large on paths crossing the Hidaka Mountains. From the corresponding lapse time of coda (65 sec), there may be a zone of concentrated heterogeneities beneath the Hidaka Mountains at the depth of 100-120 km.

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Section: Spatial Distribution Of Heterogeneities In the Hidaka Regionmentioning

confidence: 99%

Characteristics of Small-Scale Heterogeneities in the Hidaka, Japan, Region Estimated by Coda Envelope Level

Taira¹

2003

Bulletin of the Seismological Society of America

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“…Coda Q studies include Rautian and Khalturin (1978), Roecker et al (1982), Rodriguez et al (1983), Singh and Herrmann (1983), Biswas and Aki (1984), Pulli (1984), Rhea (1984), Jin et al (1985), Del Pezzo et al (1985), Jin and Aki (1988), van Eck (1988), Kvamme and Havskov (1989), Matsumoto and Hasegawa (1989), Baskoutas and Sato (1989), Oancea et al (1991), Tsuruga et al (2003), Giampiccolo et al (2004), and Goutbeek et al (2004).…”

Section: Scattering Observationsmentioning

confidence: 99%

Deep Earth Structure: Seismic Scattering in the Deep Earth

Shearer

2015

Treatise on Geophysics

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“…Coda Q studies include Rautian and Khalturin (1978), Roecker et al (1982), Rodriquez et al (1983), Singh and Herrmann (1983), Biswas and Aki (1984), Pulli (1984), Rhea (1984), Jin et al (1985), Del Pezzo et al (1985), Jin and Aki (1988), van Eck (1988), Kvamme and Havskov (1989), Matsumoto and Hasegawa (1989), Baskoutas and Sato (1989), Oancea et al (1991), Tsuruga et al (2003), Giampiccolo et al (2004), and Goutbeek et al (2004).…”

Section: S Codamentioning

confidence: 99%

Deep Earth Structure – Seismic Scattering in the Deep Earth

Shearer¹

2007

Treatise on Geophysics

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Most seismic analyses of Earth structure rely on observations of the traveltimes and waveforms of direct seismic waves that travel along ray paths determined by Earth's large-scale velocity structure. These observations permit inversions for radially averaged P wave and S wave velocity profiles as well as three-dimensional (3-D) perturbations. However, smaller-scale velocity or density perturbations cause some fraction of the seismic energy to be scattered in other directions, usually arriving following the main phase as incoherent energy over an extended time interval. This later-arriving wavetrain is termed the coda of the direct phase. Given the number of different scattering events and the complexity of the scattered wavefield, it is generally impossible to resolve individual scatterers. Instead, coda-wave observations are modeled using random media theories that predict the average energy in the scattered waves as a function of scattering angle, given the statistical properties of the velocity and density perturbations. In this way, it is possible to characterize Earth's heterogeneity at much smaller scales than can be imaged using tomography or other methods.The fact that direct seismic waves can be observed in the Earth indicates that this scattering must be relatively weak so that a significant fraction of the seismic energy remains in the primary arrivals. In contrast, scattering on the Moon is proportionally much stronger than in the Earth, preventing the easy observation of direct P and S waves at global distances (at least at the recorded frequencies of the available data) and complicating inversions for lunar structure. In addition to facilitating observations of direct arrivals, weak (as opposed to strong) scattering can also simplify modeling by permitting use of single-scattering theory (i.e., the Born approximation). However, it is now clear that accurate modeling of scattering in the lithosphere, and possibly deeper in the mantle as well, requires calculations based on multiple scattering theories. Fortunately, increased computer power makes these calculations computationally feasible.Although both body waves and surface waves exhibit scattering, the emphasis in this review is on observations and modeling of deep-Earth scattering, 695

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Detection of Localized Small-Scale Heterogeneities in the Hanshin-Awaji Region, Japan, by Anomalous Amplification of Coda Level

Cited by 4 publications

References 25 publications

Characteristics of Small-Scale Heterogeneities in the Hidaka, Japan, Region Estimated by Coda Envelope Level

Characteristics of Small-Scale Heterogeneities in the Hidaka, Japan, Region Estimated by Coda Envelope Level

Deep Earth Structure: Seismic Scattering in the Deep Earth

Deep Earth Structure – Seismic Scattering in the Deep Earth

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