The third Kurayosi explosion and the crustal structure in the western part of Japan.

Yoshii, Toshikatsu; Sasaki, Yoshimi; Tada, Takeshi; Okada, Hiroshi; Asano, Shûzô; Muramatu, Ikuei; Hashizume, Michio; Moriya, Toshio

doi:10.4294/jpe1952.22.109

Cited by 55 publications

(43 citation statements)

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“…Precise values of velocities for the layers in the crust not only beneath the Tohoku District but also beneath the southern part of Hokkaido, the Kanto District, the central and the western parts of Japan have been derived from explosion seismic observations by HOTTA et al (1964), HASHIZUME et al (1966, SASAKI et al (1970), AOKI et al (1972), OKADA et al (1973), YOSHII et al (1974), and ASANO et al (1979. These results suggest that although there is a large lateral variation of the thickness of these layers, variation of velocity is small at least beneath the land area of Japan.…”

Section: Introductionmentioning

confidence: 76%

Two-dimensional depth structure of the crust beneath the Tohoku District,the northeastern Japan arc Part I. Method and Conrad discontinuity.

1982

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A new technique for determining the three-dimensional seismic velocity structure of a crust is proposed.The principle of the technique is to relate travel time anomalies only to those thickness anomalies of the granitic and the basaltic layers, whose seismic velocities have been shown to be almost constant in the lateral direction at least beneath the land area of Japan. We determine the lateral variations of the depth of the Conrad discontinuity beneath the Tohoku District, the northeastern part of Honshu, Japan by applying the technique to arrival time data from local earthquakes. The results show that the Conrad is deep beneath the central part of the Tohoku District and becomes shallower toward both the eastern and western coast lines. They also show that the Conrad becomes deeper to the north and is located at a depth ranging from 14 to 18km.The resulting Conrad depth at the western part of the profile along the Kesennuma-Oga is consistent with that derived from explosion seismic experiment.However, our result in the eastern part of the profile suggests that the Conrad is located at a depth of about 14km, which is deeper by 6km than that derived from explosion seismic experiment.

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Section: Introductionmentioning

confidence: 76%

Two-dimensional depth structure of the crust beneath the Tohoku District,the northeastern Japan arc Part I. Method and Conrad discontinuity.

1982

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“…MIYAMACHI and MORIYA (1984) proposed a model in which an inclined low velocity zone exists and Pacific plate is confined below the low velocity zone. These results show that the structure of the region considered is complicated; that is, the average P-wave velocities of the crust and upper mantle are extremely low compared with those in other regions in Japan (e.g., AOKI et al, 1972;OKADA et al, 1973;SASAKI et al, 1970;YOSHII and ASANO, 1972;YOSHII et al, 1974). If the standard travel-time tables (e.g., ICHIKAWA and MOCHIZUKI, 1971) are used for hypocenter determination in the present region, the parameters to be determined for hypocenters must include systematic large errors.…”

mentioning

confidence: 86%

Collision of Forearcs and Overlapped Deep Seismic Zone in the Transitional Zone Between the Northern Honshu and Kurile Arcs

Moriya

1986

J,Phys,Earth

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“…The underground structure used to calculate Green's functions is given in Table 1(c). This structure is based on the P-wave crustal structure in the western part of Japan by Yoshii et al (1974), and the V p /V s structure by Ichikawa and Mochizuki (1971).…”

Section: The Tonankai Earthquake Of December 7 1944mentioning

confidence: 99%

Source rupture processes of the 1944 Tonankai earthquake and the 1945 Mikawa earthquake derived from low-gain seismograms

Nakamura²,

2014

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In the 1940's, several destructive earthquakes occurred in western Japan. Seismograms in this period were usually recorded on smoked paper and the quality was poor compared to modern digital data. But the recent development of image processing technology enabled us to reconstruct feasible waveform data, whereby we investigated source rupture processes of two devastating earthquakes: the Tonankai earthquake (M7.9) of December 7, 1944, and the Mikawa earthquake (M6.8) of January 13, 1945. The results for the Tonankai earthquake show that the source roughly consists of a single asperity with a length scale of 100 km, having no segment structure with a smaller length-scale. Such a feature seems to be reflected to the sea bottom topography above the source region. The main source parameters are as follows: the seismic moment = 1.0 × 10 21 Nm (Mw=7.9); the fault area = 140 km × 80 km; (strike, dip, rake) = (225• , 15• , 79 • ); the maximum and averaged dislocations = 4.4 m and 3.0 m, respectively. The analysis of the seismograms for the Mikawa earthquake shows that the source is a reverse fault with a slight left-lateral component. The pressure axis is directed to ENE-WSW, which is a little rotated from the EW compression axis prevailing in western Japan. This fault can be regarded as the southern extension of the Nobi earthquake fault system. The main source parameters are as follows: the seismic moment = 1.0 × 10 19 Nm (Mw=6.6); the fault area = 20 km × 15 km; (strike, dip, rake) = (135• , 30• , 65 • ); the maximum and averaged dislocations are 2.1 m and 1.1 m, respectively. The slip distribution mainly consists of two asperities: the one near the hypocenter and the other 10-15 km northwest from it. The heavily damaged area is well correlated with the northwestern asperity.

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The third Kurayosi explosion and the crustal structure in the western part of Japan.

Cited by 55 publications

References 0 publications

Two-dimensional depth structure of the crust beneath the Tohoku District,the northeastern Japan arc Part I. Method and Conrad discontinuity.

Two-dimensional depth structure of the crust beneath the Tohoku District,the northeastern Japan arc Part I. Method and Conrad discontinuity.

Collision of Forearcs and Overlapped Deep Seismic Zone in the Transitional Zone Between the Northern Honshu and Kurile Arcs

Source rupture processes of the 1944 Tonankai earthquake and the 1945 Mikawa earthquake derived from low-gain seismograms

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