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The Shikotan Earthquake of October 4, 1994: Lithospheric earthquake

Kikuchi, Masayuki and Kanamori, Hiroo (1995) The Shikotan Earthquake of October 4, 1994: Lithospheric earthquake. Geophysical Research Letters, 22 (9). pp. 1025-1028. ISSN 0094-8276. doi:10.1029/95GL00883.

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A large M_w=8.2 earthquake occurred off Shikotan Is., one of the Kurile Is., on October 4, 1994. We inverted 32 body-wave records to determine the rupture pattern using an iterative deconvolution method. The mechanisms of the subevents were allowed to vary during rupture. The source parameters obtained are: the location of the initial break = (43.48°N, 147.40°E); the centroid depth = 56 km; (strike, dip, rake) = (49°, 75°, 125°) for the total source; the seismic moment M_o = 2.6×10^(21) Nm (M_w=8.2); source time duration T = 42 s; the average rupture velocity ν = 2.5 km/s. We also determined the mechanism using long-period Love and Rayleigh waves from 14 stations. The solution for a finite source distributed over a depth range from 0 to 90 km is (strike, dip, rake) = (54°, 76°, 129°) with Mo = 2.3×10^(21) Nm, in good agreement with that from body waves. Referring to the extent of the aftershock area and the subevent distribution, we estimated the fault area S = 120 × 60 km², the average slip D=5.6m, and the stress drop Δσ=11 MPa. We computed synthetic waveforms as well as static displacements using either the steep or the low-angle plane as the fault plane, and found that the steep-dip fault model fits the data better. Our result (the mechanism, large centroid depth, high stress drop) strongly suggests that the 1994 Shikotan earthquake is a lithospheric earthquake: an intra-plate event that ruptures through a substantial part of the subducting oceanic lithosphere. This type of lithospheric earthquake is relatively common.

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Kanamori, Hiroo0000-0001-8219-9428
Additional Information:Copyright 1995 by the American Geophysical Union. (Received January 13, 1995; revised February 28, 1995; accepted February 28, 1995.) Paper number 95GL00883. We thank Kei Katsumata and Hiromichi Tsuji for permitting us to use their results. We also thank Göran Ekstrom, Yuichiro Tanioka, Hitoshi Kawakatsu, and Hong-Kie Thio for letting us examine their moment determinations. This research was partially supported by the Grant-In-Aid for Scientific Research No. 04452067 from the Ministry of Education, Japan, and by the National Science Foundation Grant EAR-9303804, USA. Contribution No. 5500, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.
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Ministry of Education (Japan)04452067
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Caltech Division of Geological and Planetary Sciences5500
Issue or Number:9
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ID Code:51012
Deposited By: George Porter
Deposited On:29 Oct 2014 20:25
Last Modified:10 Nov 2021 19:04

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