Phenomena similar to tsunami in Russian internal basins

1. Introduction

[2] The recent catastrophic tsunami, which occurred on 26 December 2004, in the Indian Ocean, attracted the attention of specialists to a serious analysis of tsunami danger in the regions, where this phenomenon was not actually considered dangerous, and the tsunami warning services did not exist. Speaking about tsunami in Russia, first of all, Far East is mentioned as the region, in which tsunami occurs relatively frequently, and tsunami warning service has been developed. Numerous literature sources exist with tsunami description at the Pacific coast of Russia. Here, we mention a few reviewing publications [Shchetnikov, 1990; Soloviev, 1978; Soloviev and Ferchev, 1961; Zayakin, 1996]. Historical data together with numerical publications became the basis for developing a scheme of tsunami zoning of Far East [Go et al., 1988]. In the last years, new occurrences of tsunami were recorded in Far East. Among them the catastrophic Shikotan tsunami on 5 October 1994 [Ivashchenko et al., 1996; Yeh et al., 1995], which actually confirmed the validity of the developed scheme of tsunami zoning. At present, the research of traces of paleo-tsunami (strong tsunami in the past) has been developed in Far East. In summer 2005, one of the authors (ID) took part in one of such expeditions on Kunashir and Shikotan islands. We also note that catastrophic Indonesian tsunami in 2004 was recorded by pressure gauge in SeveroKurilsk, which emphasizes one more time the global character of tsunami propagation in the World Ocean.

[3] As to the other regions of Russia, no tsunami warning systems exist there, and tsunami risk studies have been only started there. First of all, we note more than 20 cases of tsunami in the Black Sea, which occurred during the entire historical period [Dotsenko, 1995; Nikonov, 1997; Yalciner et al, 2004; Zaitsev, 2006]. The major part of them was local and was induced by earthquakes in the sea. Approximately 10 weak tsunamis are known in the Caspian Sea, the major part of which are related to underwater mud volcanism [Dotsenko, et al., 2000; Nikonov, 1996; Zaitsev et al., 2004], (E. Pelinovsky, preprint, 1999). Two occurrences of paleo-tsunami (approximately 10000 years ago) were found in the Baltic Sea [Morner, 1999]. We also note a tsunami of asteroid origin in the Barents Sea [Shuvalov et al, 2002]. We emphasize that such kind of events can occur in any place (not necessarily in the seas and oceans), and occurred already in Russia. For example, 350 mln. years BP, falling of an asteroid in the region of Kaluga (at that time covered with sea) led to the occurrence of tsunami waves [Masaitis, 2002]. At present, much attention is focused on tsunami waves of asteroid origin [Kharif and Pelinovsky, 2005].

Figure 1

[4] At the same time, tsunamis and phenomena similar to tsunami occur not only in seas and oceans but also in the so-called internal basins, rivers, lakes, and other reservoirs. Three strongest tsunamis caused by landslides in Italian artificial water supply reservoirs are known very well: Vajont and Pontesei, (see, for example, [Panizzo et al., 2005]). One of the events in 1963 that took away about 2000 lives is described well in literature (including publications in Russian) [Mamradze et al., 1991]. Wave height in Vajont reservoir reached 235 m. We note that such events occurred in the Alps in prehistorical time. For example, in Lake Lucerne in Switzerland a wave whose height reached 3 m was generated by a landslide [Schnellmann et al., 2002]. Several cases of tsunamis of seismic origin occurred in Lake Kineret (Israel) [Amiran et al., 1994]. Resonance oscillations in Lake Hebden, (Montana) 11.5 long were recorded after an earthquake with magnitude 7.5 and potential tsunami risk in Lake Tahoe in California-Nevada generated by strong earthquakes is specially described in [Ichinose et al., 2000]. Finally, we mention tsunamis of volcanic origin in lakes. For example, in 1305, a series of pyroclastic flows descended from Mount Tarawera to Lake Tarawera, which caused tsunami waves reaching 6-7 m on the opposite coast of the lake [De Lange et al., 2002]. Eruption of a volcano near Lake Taal in Philippines generated a 5-m tsunami [De Lange and Healy, 2001]. Similar events occurred also in Russia, and the first list of such events is given in papers [Didenkulova, 2005, 2006] and also provided by Didenkulova et al (Tsunami in 1806 in Kozmodemiansk on the Volga River, 2006, in press). In our study we shall present data evidence about historical phenomena similar to tsunami in internal basins of Russia. A total of nine events were distinguished in different regions of Russia during the period from 1597 to 2006 so that the frequency of their occurrence is approximately 45-50 years (during the last 200 years, tsunami appeared approximately each 25 years). The geography of phenomena similar to tsunami is shown in Figure 1. Seven events can be considered reliable. Earthquakes and landslides are equiprobable sources of these events (each cause generated four tsunamis), and one event was caused by a volcano eruption. They confirm the existence of tsunami risk in all water reservoirs and the necessity of informing the population about this danger.