Spatial and Temporal Variations in Coda Attenuation Associated with the 2011 Off the Pacific Coast of Tohoku, Japan (Mw 9) Earthquake

Padhy, Simanchal; Takemura, Shunsuke; Takemoto, Toshihiko; Maeda, Takuto; Furumura, Takashi

doi:10.1785/0120120026

Cited by 13 publications

(8 citation statements)

References 31 publications

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“…The analysis period of this study is January 2012-October 2014, i.e., after the 2011 off the Pacific coast of Tohoku earthquake, and several researchers have reported a temporal change in the scattering environment in the crust in northeast Japan after the earthquake (e.g., Takagi and Okada 2012;Kato et al 2013;Padhy et al 2013). These studies reported that there are significant variations in the S-wave velocity, or the scattering environment in/around the source area, but no systematic and/or significant variations in the other areas where this study area is included.…”

Section: Discussionmentioning

confidence: 99%

“…S-coda waves consist of S-waves scattered by the heterogeneity of the crust (Aki 1969), and the attenuation of S-coda waves, represented as coda Q, is considered to be a good indicator of the stress state in the crust (Aki 1980;Hiramatsu et al 2000). Padhy et al (2013) analyzed the temporal changes in coda Q associated with the 2011 off the Pacific coast of Tohoku earthquake along the Pacific coast of northeastern Japan. They reported that, inside the source region, the value of coda Q with center frequencies of 1.25-3.5 Hz decreased by about 10-16% after the earthquake.…”

Section: Introductionmentioning

confidence: 99%

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Spatial variation in coda Q in the northeastern part of Niigata–Kobe Tectonic Zone, central Japan: implication of the cause of a high strain rate zone

Dojo

Hiramatsu

2017

Earth Planets Space

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We have analyzed the spatial variation in coda Q in the northeastern part of a high strain rate zone, the Niigata-Kobe Tectonic Zone (NKTZ), to investigate the cause of the high strain rate by correlating coda Q with the differential strain rate and the S-wave velocity. The spatial distributions of coda Q in the 2-4 and 4-8 Hz frequency bands are found to be negatively correlated with the differential strain rate. Coda Q in the 2-4 Hz frequency band is correlated spatially with the S-wave velocity at a 25 km depth, as has been reported previously. We also find a positive correlation between the perturbation of the S-wave velocity at a 10 km depth and coda Q in the 4-8 Hz frequency band, implying that the spatial distribution of coda Q in this frequency band is mainly attributed to the heterogeneity of the upper crust. This feature is different from that of the central part of the NKTZ reported previously, which indicates a difference in the cause of the high strain rate. Therefore, we suggest that the high deformation rate in the upper crust, which is characterized by a thick sediment basin, as well as that in the ductile lower crust, contributes to the generation process of the high strain rate on the surface in the northeastern part of the NKTZ.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spatial variation in coda Q in the northeastern part of Niigata–Kobe Tectonic Zone, central Japan: implication of the cause of a high strain rate zone

Dojo

Hiramatsu

2017

Earth Planets Space

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“…Padhy et al (2013) examined temporal changes in Q C −1 associated with the Tohoku earthquake using nine stations along the Pacific coast of northeastern Japan. They reported an increase of Q C −1 (decrease of coda Q) by about 10% to 16% for the frequency bands of 1.25 to 3.5 Hz after the Tohoku earthquake at stations inside the source region.…”

Section: Methodsmentioning

confidence: 99%

Spatial variation in coda Q around the Nobi fault zone, central Japan: relation to S-wave velocity and seismicity

Tsuji

Hiramatsu

2014

Earth Planet Sp

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We investigate the spatial variation in coda Q around the Nobi fault zone in a high strain rate zone to assess the relation between coda Q, shear wave velocity, and seismicity. Waveform data were obtained from dense seismic observations. Low coda Q that follows the Niigata-Kobe Tectonic Zone in the high strain rate zone is distinct at the lowest frequency band of 1 to 2 Hz. However, at higher frequencies, such a spatial pattern in coda Q is unclear. A good positive correlation was found between coda Q at the 1-to 2-Hz frequency band and the S-wave velocity perturbation at 25-km depth, which suggests that the coda Q reflects the ductile deformation below the brittle-ductile transition zone. Furthermore, coda Q at the 1-to 2-Hz frequency band correlates negatively with seismicity at 10-to 15-km depth, which implies that there is a high stressing rate in the low coda Q area. These facts, together with results of previous studies, imply that a high deformation rate below the brittle-ductile transition zone produces the high strain rate observed by the Global Positioning System (GPS) on the surface in this region.

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“…The 2011 off the Pacific coast of Tohoku earthquake (hereafter referred to as the 2011 Tohoku earthquake) caused large-scale coseismic and postseismic crustal deformations over the Japanese islands. These deformations have modified the crustal heterogeneities around the source area and caused a decrease of coda Q with center frequencies of 1.25-3.5 Hz along the Pacific coast of northeastern Japan (Padhy et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Temporal stability of coda Q in the northeastern part of an inland high strain rate zone, central Japan: implication of a persistent ductile deformation in the crust

Dojo¹,

Hiramatsu²

2019

Earth Planets Space

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We have analyzed the temporal variation in coda Q in the northeastern part of an inland high strain rate zone, the Niigata-Kobe Tectonic Zone (NKTZ), in central Japan, to investigate the response of coda Q to the modification of the strain field induced by the 2011 Tohoku earthquake (Mw 9.0). We observe no statistically significant temporal variations in the spatial distribution of coda Q as the whole analyzed area, implying that the crustal deformation induced by the 2011 Tohoku earthquake has provided no significant temporal variation in crustal heterogeneity as the whole analyzed area. For the middle frequency bands, before and after the 2011 Tohoku earthquake, we have commonly found a negative correlation between the spatial distributions of coda Q and the differential strain rate and a positive correlation between the spatial distributions of coda Q and the perturbation of S-wave velocity in the upper crust. These features, together with previous works, suggest that the ductile deformation with a high rate in the upper crust plays an important role in generating the high strain rate in the analyzed area not only before but also after the 2011 Tohoku earthquake. In other words, the existence of a persistent ductile deformation in the upper crust contributes essentially to the generation process of the high strain rate in the northeastern part of the NKTZ. It is important to note that the location of the persistent ductile deformation in the northeastern part of the NKTZ, mainly in the upper crust, differs from that in the central part of the NKTZ, mainly in the lower crust. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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Spatial and Temporal Variations in Coda Attenuation Associated with the 2011 Off the Pacific Coast of Tohoku, Japan (Mw 9) Earthquake

Cited by 13 publications

References 31 publications

Spatial variation in coda Q in the northeastern part of Niigata–Kobe Tectonic Zone, central Japan: implication of the cause of a high strain rate zone

Spatial variation in coda Q in the northeastern part of Niigata–Kobe Tectonic Zone, central Japan: implication of the cause of a high strain rate zone

Spatial variation in coda Q around the Nobi fault zone, central Japan: relation to S-wave velocity and seismicity

Temporal stability of coda Q in the northeastern part of an inland high strain rate zone, central Japan: implication of a persistent ductile deformation in the crust

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