Geologist Views of the Predicted Tokai Earthquake

Akira Tokuyama

doi:10.20965/jdr.2009.p0282

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JDR Vol.4 No.3 pp. 282-290

(2009)

doi: 10.20965/jdr.2009.p0282

Paper:

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Geologist Views of the Predicted Tokai Earthquake

Akira Tokuyama

Fuji-Tokoha University, 325 Oobuchi, Fuji City, Shizuoka 417-0801, Japan

Received:

February 13, 2009

Accepted:

April 13, 2009

Published:

June 1, 2009

Keywords:

strength of crust, strike-slip fault, drag zone, creeping, plastic deformation

Abstract

1. The hypothesis of the Tokai earthquake is based on assumption of elastic and robust slab of crust (wider than 9,000 km² and 15 km thick) for the overriding mass of the underthrust, to which the Philippine Sea Plate is subducting. In seismology the crust is assumed elastic, homogeneous and strong enough to sustain strain energy of the gigantic earthquake, M>8. Geology of the region suggests the crust is neither elastic nor strong enough. It consists of compound slabs of folded strata of accretionary sediments. It is uncommon to consider such robust slab in this area. 2. The Fossa Magna is a large strike slip fault running from Suruga Bay to Itoigawa to the north. It follows a wide drag zone in the west, in which the focal area of the predicted Tokai earthquake is situated. The drag zone has been produced by slow creeping over 6 Ma. The creeping of the left-lateral fault is still active. Part of strain energy by subducting plates may be released by the creeping. 3. The Nankai trench is considered to extends into the Suruga Bay. In geology the bay is a canyon, seaward extension of the Fossa Magna, by which the trench is displaced and dragged to north to the south of Izu peninsula.

Cite this article as:

A. Tokuyama, “Geologist Views of the Predicted Tokai Earthquake,” J. Disaster Res., Vol.4 No.3, pp. 282-290, 2009.

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References

[1] R. D. Ballard, “Exploring our Living Planet,” National Geogr. Soc., 366p, 1983.
[2] T. Eguchi and S. Hori, “Morphology of the Philippine Sea Plate Slab just beneath the Tokyo Metropolitan Area and its Vicinity, Japan,” J.Geogr., Vol.116, Nos.3/4, pp. 325-369, 2007.
[3] O. Fujiwara, J. Komatsubara, and Y. Sawai, “Holocene earthquakes along the Nankai Trough and sedimentary facies of the Ukishimaga- hara lowland beside Suruga Bay, Shizuoka Prefecture, Central Japan,” a preliminary report Res. Active Faults and Paleo-Earthq., No.6, pp. 89-106, 2006.
[4] J. Gilluly, A.C. Waters, and A. O. Woodford, “Principles of Geology,” 3rd Ed., 687p, Freeman/Toppan, 1968.
[5] Headquarters for Earthquake Research Promotion, “Earthquake Activity of Japan - Regional Characteristics seen from quake damages,” Suppl. Ed., 39p, Res. Assoc. Earthq. Prediction, 1999.
[6] K. Ishibashi, “Reconsideration about soon-to-occur large earthquake in the Tokai district - Suruga Bay Earthquake,” Prer. Papers Seismological Soc., Japan, No.2, pp. 30-34, 1976.
[7] T. Kimura and A. Tokuyama, “Geosynclinal Prisms and Tectonics in Japan,” Mem. Geol. Soc., Japan, No.5, pp. 9-21, 1971.
[8] T. Kobayashi, “The Triassic Akiyoshi Orogeny,” Geotekt. Symposium zu Ehren von H. Stille. pp. 85-101, 1956.
[9] T. Nishimura, T. Sagiya, and R. S. Stein, “Crustal block kinematics and seismic potential of the northernmost Philippine Sea Plate and Izu microplate, central Japan inferred from GPS and leveling data,” J. Geophys. Res. Vol.112, B05414, 2007.
[10] T. Terada and T. Tsuboi, “Geophysics,” 4th Ed. Iwanami Ser. Text Books, 10, 202p, 1938.
[11] A. Tokuyama, “Faltungsstockwerke in der Ojika-Halbinsel Nordostjapans,” Sc. Papers, Coll. Gen. Educ., Univ. Tokyo, Vol.15, No.2, pp. 217-236, 1965.
[12] “Ueber den Faltenbau der mittleren Chichibu-Zone im Sakuradani- Gebiet Ostshikoku, mit bhesonderen Beruecksichtigungen ueber den Unterschied in Faltungsstockwerken zwischen Nordost- und Suedwestfluegel der Sakawa-Faltenzone in Jaan,” Ibid., Vol.18, pp. 65-98, 1968.
[13] “Tektonische Probleme des Grundgebirges im Shizuoka-Gebiet (I),” Bull.Educ, Fac. Shizuoka Univ., Natural Sc. Ser., No.23, pp. 67-86, 1972.
[14] “Structural Analysis of Deformation in the Shimanto Terrane in the upper Ooi River, Central Japan,” Hyogo Univ. Teacher Educ. Jour., No.2, pp. 223-246, 1983.
[15] K. Handa, “Structural Framework and Recent Crustal Movements of the Fossa Magna,” J.Geogr, Vol.87, No.2, pp. 14-27, 1978.
[16] S. Yoshida, “Kinabalu Fault, a large strike-slip fault in Sabah, East Malaysia,” Geol. & Palaeont. Southeast Asia., Vol.14, pp. 171-188, pls.23, 24., 1974.
[17] S. Yoshida, et al., “Neogene geology of the Shimobe area, Yamanashi Pref. in the southern Fossa Magna with special reference to shear folding,” GeoSc. Rept., Shizuoka Univ. No.4, pp.1-18, 1979.

This article is published under a Creative Commons Attribution-NoDerivatives 4.0 Internationa License.

[1] [1] R. D. Ballard, “Exploring our Living Planet,” National Geogr. Soc., 366p, 1983.

[2] [2] T. Eguchi and S. Hori, “Morphology of the Philippine Sea Plate Slab just beneath the Tokyo Metropolitan Area and its Vicinity, Japan,” J.Geogr., Vol.116, Nos.3/4, pp. 325-369, 2007.

[3] [3] O. Fujiwara, J. Komatsubara, and Y. Sawai, “Holocene earthquakes along the Nankai Trough and sedimentary facies of the Ukishimaga- hara lowland beside Suruga Bay, Shizuoka Prefecture, Central Japan,” a preliminary report Res. Active Faults and Paleo-Earthq., No.6, pp. 89-106, 2006.

[4] [4] J. Gilluly, A.C. Waters, and A. O. Woodford, “Principles of Geology,” 3rd Ed., 687p, Freeman/Toppan, 1968.

[5] [5] Headquarters for Earthquake Research Promotion, “Earthquake Activity of Japan - Regional Characteristics seen from quake damages,” Suppl. Ed., 39p, Res. Assoc. Earthq. Prediction, 1999.

[6] [6] K. Ishibashi, “Reconsideration about soon-to-occur large earthquake in the Tokai district - Suruga Bay Earthquake,” Prer. Papers Seismological Soc., Japan, No.2, pp. 30-34, 1976.

[7] [7] T. Kimura and A. Tokuyama, “Geosynclinal Prisms and Tectonics in Japan,” Mem. Geol. Soc., Japan, No.5, pp. 9-21, 1971.

[8] [8] T. Kobayashi, “The Triassic Akiyoshi Orogeny,” Geotekt. Symposium zu Ehren von H. Stille. pp. 85-101, 1956.

[9] [9] T. Nishimura, T. Sagiya, and R. S. Stein, “Crustal block kinematics and seismic potential of the northernmost Philippine Sea Plate and Izu microplate, central Japan inferred from GPS and leveling data,” J. Geophys. Res. Vol.112, B05414, 2007.

[10] [10] T. Terada and T. Tsuboi, “Geophysics,” 4th Ed. Iwanami Ser. Text Books, 10, 202p, 1938.

[11] [11] A. Tokuyama, “Faltungsstockwerke in der Ojika-Halbinsel Nordostjapans,” Sc. Papers, Coll. Gen. Educ., Univ. Tokyo, Vol.15, No.2, pp. 217-236, 1965.

[12] [12] “Ueber den Faltenbau der mittleren Chichibu-Zone im Sakuradani- Gebiet Ostshikoku, mit bhesonderen Beruecksichtigungen ueber den Unterschied in Faltungsstockwerken zwischen Nordost- und Suedwestfluegel der Sakawa-Faltenzone in Jaan,” Ibid., Vol.18, pp. 65-98, 1968.

[13] [13] “Tektonische Probleme des Grundgebirges im Shizuoka-Gebiet (I),” Bull.Educ, Fac. Shizuoka Univ., Natural Sc. Ser., No.23, pp. 67-86, 1972.

[14] [14] “Structural Analysis of Deformation in the Shimanto Terrane in the upper Ooi River, Central Japan,” Hyogo Univ. Teacher Educ. Jour., No.2, pp. 223-246, 1983.

[15] [15] K. Handa, “Structural Framework and Recent Crustal Movements of the Fossa Magna,” J.Geogr, Vol.87, No.2, pp. 14-27, 1978.

[16] [16] S. Yoshida, “Kinabalu Fault, a large strike-slip fault in Sabah, East Malaysia,” Geol. & Palaeont. Southeast Asia., Vol.14, pp. 171-188, pls.23, 24., 1974.

[17] [17] S. Yoshida, et al., “Neogene geology of the Shimobe area, Yamanashi Pref. in the southern Fossa Magna with special reference to shear folding,” GeoSc. Rept., Shizuoka Univ. No.4, pp.1-18, 1979.