INTRODUCTION

Seismological observations constitute integral part and one of major components of comprehensive geoscientific studies anywhere on the Earth. A special role of the above in the comprehensive studies is determined by the fact that unlike many other geological methods they provide an output information on the environment, geological interpretation of which is to the lesser extent subject to estimate and personal views of particular executors. In addition, seismic method is the only remote geophysical method with nearly unlimited coverage affording the scope of research into poorly accessible areas which is especially demanding for the Arctic Region. The scientific and operational value of seismic data applications apparent. The only fact establishing the existence or absence of a higher seismicity considerably affects both our understanding of the modern geological and tectonic setting of the region, and the assessment of its potential and expediency of its industrial exploration.

As a geographic unit, the Arctic comprises the Arctic Ocean and islands, adjacent parts off the Pacific and Atlantic Oceans, northern margins of the American and European continents, and Greenland. Strictly speaking, the Arctic border has been conventionally marked along the southern termination of the tundra zone, and in this case, it covers an area of 27 million square kilometers with allowance for significant deviations off the line in different regions. Most often the border is marked along the North Polar Circle (21 million square kilometers). We have also adopted the latter interpretation of the Arctic border.

At present, a large volume of instrumental materials has been gathered to prove the existence in the Arctic of major sufficiently active seismic zones. Seismic events have been reported to have magnitudes as high as 6 and even 7. Data on spatial distribution of earthquakes, their intensity and focal mechanism solutions constituting the base of many papers on the tectonics of the Central Arctic Basin , its shelf seas and coasts have become an invaluable contribution to gaining a better geological insight into this polar area. Until recently the application aspect of seismic information on the Arctic has been much lesser used, which is cause by its low population level and fairly poor industrial development. However, the role of application will be growing fast, and the assessment of the effect of seismic macroocurrences will be equally demanding both for onshore and offshore areas. Marine drilling rigs are now operating on the seismically active shelves off the Beaufort and Norwegian seas. The outlook of the petroleum potential of the Barents and Laptev seas seems to be promising.

To the author¸s best knowledge, a vast majority of scientific papers concerning seismicity and seismic tectonics of the Arctic address discussion of particular regions, basic notice being taken of the Mid-Arctic Belt, which is by all means quite explicable. Most post-war summary studies based on a fairly large volume of factual material concerned mainly the European part of the Arctic Region. In addition, since their advent a new and fairly vast amount of information has been obtained. The most updated summary has been reported from "The Arctic Ocean Regions", Chapter entitled "Seismicity and focal mechanisms..." (The Arctic Ocean Region,1990). However, a similar amount of seismic evidence is disseminated in many other chapters dedicated to particular Arctic regions, which to a certain extent, prevents from attaining a full understanding of the problem. Moreover, the evidence on focal mechanisms are mainly restricted to the second half of the 1970s. More recent national papers similar to the present one do not exist whatsoever.

The purpose of this publication is somewhat to fill the gap. It contains and provides an analysis of the information on the history of seismic research into the Arctic, distribution of the Arctic earthquakes and stress mechanisms in the foci, it also traces the relationships between seismicity and tectonics expressing some ideas about the geodynamics of active seismic zones in the Arctic and their rank in the row of the Earth¸s seismically active zones.

The Arctic Seismic Data Bank made by VNIIOkeangeologia was adopted as a factual base. It contains information on earthquakes in the Arctic and adjacent areas over the entire period of instrumental observations.

The applied value of this paper is that the factual information contained therein and the set of geological conclusions in combination with the data bank constitute the base for studies of seismic zonation and microzonation of the Arctic Region, and at this particular view, the paper may be regarded as an initial necessary step of these studies. The paper presents assessments of seismic hazards for the offshore Eurasian Subbasin of the Arctic Ocean and adjacent shelf seas which were made by the author some 25 years ago, and according to subsequent investigations (Assinovskaya,1994) basically are still in force at present.

English version of the book is a newer edition comparing with Russian publication of 1995 year owing to utilization of additional data about focal mechanisms and magnitudes of the Arctic earthquakes.

In the solution of the problems the author was largely assisted by scientific editors I.S.Gramberg, RAS Academician, Yu.E.Pogrebitskiy, RAS Corresponding Member, and V.V.Verba, M.L.Verba, E.E.Musatov, V.E.Volk, B.G.Lopatin, A.A.Krasilshchikov, D.V.Semevsky, V.I.Ustritskiy, V.D.Dibner, O.P.Dundo, B.I.Kim, B.M.Kozmin, B.S.Imaev, B.A.Assinovskaya, A.F.Grachev, A.P.Lazareva, I.P.Gabsatarova, A.A.Vinnik and others, who kindly made available materials and provided their comments, advice and recommendations. The author extends his sincere acknowledgment to the above persons. Besides, the invaluable help of faithful and reliable Arctic expedition mates, primarily, B.T.Barychev and V.V.Vasiliev, is also greatly appreciated.