RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 8, ES5003, doi:10.2205/2006ES000210, 2006
Numerical simulation of the 7 February 1963 tsunami in the Bay of Corinth, GreeceL. I. Lobkovsky1, R. Kh. Mazova2, I. A. Garagash3, and L. Yu. Kataeva2 1P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia2Nizhny Novgorod State Technical University, Nizhniy Novgorod, Russia 3Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia Contents
Abstract[1] The paper addresses the event that occurred in the Bay of Corinth, Greece, on 7 February 1963. The tsunami was produced by a submarine landslide in the mouth of the local Salmenikos River. The paper presents preliminary numerical results obtained in terms of an elastoplastic model for the surface water waves generated by the landslide and propagated onto the coast. The wave propagation is analyzed as a function of the landslide movement. The inferred results are compared with those obtained in terms of other models. Introduction[2] Recently the problem of tsunami generation due to seismic or aseismic submarine rockfalls or coastal landslides has received much attention. An example is the catastrophic tsunami produced by the 17 July, 1998 ( M = 7.1) earthquake in Papua New Guinea (PNG) (e.g., see [Mazova et al., 2004]). Although the PNG tsunami generation mechanism is still debated, several observation and model data indicate that a submarine landslide was the tsunami cause [Mazova, 2003; Papadopoulos, 2000]. Moreover, detailed descriptions of other cases of landslide-induced tsunamis have been published over the last 50 years (for example, in the South Aegean Sea (Greece) in 1956; in Lituya Bay (Alaska) in 1958, in the city of Aegion (Greece) in 1963; in the Vayont valley (Italy) in 1963; in Norway and Nice (France) in 1979; in Skagway Harbor (Alaska) in 1994; in Izmit (Turkey) in 1999; and Fatu Hiva (French Polynesia) in 1999 (e.g. see [Fine et al, 1998; Mazova, 2003; Murti, 1981; Papadopoulos, 2000])). [3] In particular, as was shown in [Papadopoulos, 2000], a landslide-induced tsunami is a rather frequent phenomenon off the Greece coasts. For example, the tsunami wave that arose after the strong ( M = 7.5) 7 July, 1956 earthquake in the South Aegean Sea was due to not only a seismic fault motion but also a seismically induced slide of submarine sedimentary masses. Another example is the local strong tsunami generated by the aseismic landslide of 7 February 1963, in the Aegion area of the western Bay of Corinth (central Greece). [4] Statistical analysis and computations show that submarine and subaerial landslides can generate tsunami waves of a considerable height at the coast near their source [Mazova, 2003]. The length of such a wave is a few kilometers, and its height rapidly decreases due to frequency dispersion. On the contrary, the propagation range of tsunamis generated by a fault is very long, and their heights in open ocean are relatively small. Their wavelength is of the order a few hundreds of kilometers, while the height of wave decreases slowly because of the weakness of dispersion effects. A landslide-generated tsunami often results in catastrophic consequences [Mazova, 2003] and, therefore, the problem of landslide-generated waves along an open coastline or in a closed water area is of great practical interest for engineering in coastal zones. [5] Significant progress has been made in the last decade in both numerical simulation of landslide-induced tsunamis and development of analytical models for an adequate description of the tsunami generation [Mazova, 2003]. The most often used are the rigid block model [Iwasaki, 1997] and viscous or viscoplastic models [Jiang and LeBlond, 1993, 1994]. However, as was noted by Fine et al, [1998], the rigid block model overestimates the responses of the water surface to submarine disturbances, whereas viscous/viscoplastic models underestimate it. Therefore, to adequately model a tsunami from a submarine landslide, a model is required that takes into account both the detailed structure of the landslide body and the mechanical properties of landslide-body constituents characterizing its behavior during the landsliding process.
The Tsunami of 7 February 1963 in the Bay of Corinth (Greece)[7] The Bay of Corinth is a scoop-like tectonic structure rapidly widening in the southerly direction due to the stress field, and this results in high seismicity of the region related to an E-W trending fault. The fault is located between the mainland of Greece in the north and the Peloponessus Peninsula in the south and is enclosed in a water basin supplying sediments the northern and southern coasts of the bay (Figure 1). Intense tectonic activity often associated with fractures in sedimentary masses leads to the formation of steep submarine slopes. As a result, generation of both seismic and aseismic (landslide-induced) tsunamis is an additional geophysically important feature of the Bay of Corinth. [8] A typical landslide-induced tsunami in the Bay of Corinth was the wave of 7 February 1963, whose characteristics have been studied in detail [Papadopoulos, 2000]. The maximum wave height reached 5-6 m at the southern coast. Field observations [Galanopoulos et al., 1964] leave no doubts that the tsunami was caused by a sudden aseismic seaward landslide of the submarine slope overloaded by sedimentary masses (57,000 m3 in volume) that were accumulated in the mouth of the local Salmenikos River on the southern coast. The sliding masses were mostly submarine. Numerical Simulation and Results
[10] After the situation becomes unstable, the sliding process continues due to the accumulated potential energy. We introduced an initial dynamic action on the landslide process equivalent to a moderate earthquake and lasting for 6 s (Figure 2b) [Garagash et al., 2003].
[12] At the second stage, we performed a numerical simulation of landslide-generated surface water waves on the basis of the nonlinear system of shallow water equations with the use of a specially modified explicit difference scheme including the check for stability conditions (see below).
[14] The above modeling results obtained for the landslide movement were used for numerical simulation of the landslide-generated surface water wave. The wave generation was computated using the ordinary nonlinear system of shallow water equations, which can be written as
[15] To solve numerically the system of equations (1) and (2), we used an explicit two-layer scheme of the first order in time and the second order in spatial coordinates:
Conclusion[18] The data of observations in the Bay of Corinth indicate that, in the place of the landslide origin, water first receded from the shore and then returned, producing a run-up of 5-6 m. The numerical simulation of the tsunami wave run-up performed in this study showed that estimates obtained after the generation and propagation of the wave to the isobath x = -200 m agree well with observational data, thereby supporting the validity of the numerical schemes chosen in this study. Moreover, as was shown by Jiang and LeBlond [1993, 1994], who considered viscous and viscoplastic models of a landslide and solved this problem in a long-wave approximation for both the landslide and the generated wave, the generated wave first recedes from the shoreline at the initial time moment of the landslide movement, after which an elevation wave starts forming. Thus, the solution patterns obtained by Jiang and LeBlond [1993, 1994] and in our work are qualitatively similar; however, the analysis of the landslide movement in terms of an elastoplastic model, incorporating real data on sediments at the landslide origin and taking into account the strength reduction in the ground during the development of plastic deformations, provides the most correct (at present time) results of numerical simulation of tsunami wave generation and propagation and run-up values fitting better the available observational data. ReferencesFine, I. V., A. B. Rabinovich, E. A. Kulikov, R. E. Tromson, and B. D. Bornhold (1998), Numerical modelling of landslide-generated tsunamis with application to the Skagway Harbor tsunami of 3 November, 1994, in: Proc. Int. Conf. on Tsunamis (Paris 1998), p. 211, CEA Press, Paris. Galanopoulos, A., N. Delibasis, and P. Comninakis (1964), A sea wave from a slump set in motion without shock, Ann. Geol. Pays Hellen, 16, 93. Garagash, I. A., and V. A. Ermakov (2001), Use of geological-geophysical models for the simulation of the crustal stress state: A case study of Sakhalin Island and the Northern Tien Shan, in: Proc. III Scientific Conf. "Seismicity Problems in the Far East (in Russian), p. 33, IVS FEB RAS Press, Khabarovsk. Garagash, I. A., L. I. Lobkovsky, O. R. Kozyrev, and R. Kh. Mazova (2003), Generation and run-up of tsunami waves caused by a submarine landslide, Okeanologiya, 43, (2), 185. Iwasaki, S. I. (1997), The wave form and directivity of a tsunami generated by an earthquake and a landslide, Sci. Tsunami Hazards, 15, (1), 23. Jiang, L., and P. H. LeBlond (1993), Numerical modeling of an underwater Bingham plastic mudslide and the waves which it generates, J. Geophys. Res., 98, (C6), 10303. Jiang, L., and P. H. LeBlond (1994), Three-dimensional modeling of tsunami generation due to a submarine mudslide, J. Phys. Oceanogr, 24, (3), 559, doi:10.1175/1520-0485(1994)024<0559:TDMOTG>2.0.CO;2. [CrossRef] Mazova, R. Kh. (2003), Tsunamis generated by submarine landslides, Izvestiya RAEN PMM (in Russian), 4, 117. Mazova, R. Kh., G. A. Papadopoulos, and L. Yu. Kataeva (2004), The analysis of aseismic tsunami 7 February 1963 in Corinth Gulf: One-dimensional theory, Izvestiya RAEN PMM (in Russian), 9, 63. Murti, T. S. (1981), Seismic Marine Tsunami Waves (in Russian), 342 pp., Gidrometeoizdat, Leningrad. Papadopoulos, G. A., Ed. (2000), Historical Earthquakes and Tsunamis in the Corinth Rift, Central Greece, 128 pp., Inst. Geodynamics, National Observatory of Athens, 11810, Athens, Greece. Received 21 October 2006; accepted 30 October 2006; published 28 November 2006. Keywords: tsunami generation, shallow water equations, aseismic tsunami, sedimentary mass. Index Terms: 3070 Marine Geology and Geophysics: Submarine landslides; 3285 Mathematical Geophysics: Wave propagation; 4255 Oceanography: General: Numerical modeling; 4564 Oceanography: Physical: Tsunamis and storm surges. ![]() Citation: 2006), Numerical simulation of the 7 February 1963 tsunami in the Bay of Corinth, Greece, Russ. J. Earth Sci., 8, ES5003, doi:10.2205/2006ES000210. (Copyright 2006 by the Russian Journal of Earth SciencesPowered by TeXWeb (Win32, v.2.0). |