The tragedy of the KURSK nuclear submarine in August of last year in the Barents Sea precipitated an avalanche of speculations and publications on the details of the disaster and its likely causes.
Two experts of the Fedynsky Center for Regional and Geoeco- logical Studies of the RF Ministry of Natural Resources - Mikhail Lodzhevsky and Leonid Solodilov, Dr. Sc. (Tech.), have approached the problem from a slightly different perspective. On the basis of their years of experience in studies of geophysical fields (including gravitation) and using the available data on the tragic voyage of the KURSK, the two specialists analyzed the peculiarities of the sea bottom relief and its plutonic geological structure in the disaster area. Their findings can be summed up in the following way.
The disaster area belongs to a zone of conjunction of a narrow and extended Kola-Kanin monocline (with gently sloping underlying strata) stretching along the Kola Peninsula and a graben sag, filled with Riphean and Paleozoic (age of about 2.5 bln years) layers some 14 to 16 km thick. Such is the central section of the Semiostrovsky protrusion of the aforesaid ancient sediments.
There are several seamounts in this region with depths of up to 76 m. As one can see on a medium-scale (1:100,000) hydrometric map, the spot of the KURSK tragedy is located on the Murmansk shoal - an undersea microridge, stretching from the north-north- west to south-south-east. As compared with the region as a whole, this is an area of anomalously low depths of up to 105 m (some 10 km away they reach 170 m already).
An analysis of the force of gravity, conducted for this region on the basis of the State Gravimetric Map of the USSR, indicates that the seamounts and the Semiostrovsky protrusion are within the limits of a strong positive gravitational anomaly, and the spot of the disaster is in the epicentral part of its high-amplitude maximum (+55 mGal) located on a narrow strip of 25 km, stretching for 250 km along the Kola Peninsula shoreline. The horizontal gravity gradient there is abnormally high - seven times greater than its calculated value for a normal field in these latitudes. What is more, its vector direction fully matches the course of the unfortunate sub which it steered before the disaster. As it turned out, the latter was exactly perpendicular to the aforesaid gravimetric anomaly, which, in its turn, marks the border between the two major tectonic elements of the region under investigation. On the strength of the above, the two experts come to the conclusion that before the disaster the KURSK was in an extremely complex gravitational position.
Also traced in this region are certain peculiarities of the natural geo-chemical field. The disaster area is
The KURSK disaster area.
Figures on brown lines-gravity values.
in a zone featuring abnormally high levels of heavy carbohydrates which is situated in the area of scatter of these compounds with their summary content in the benthic sediments exceeding 10 - 3 %. The contour of the area matches the border of the Semiostrovsky protrusion.
The natural and spatially coinciding anomalies-gravitational and geochemical - within the limits of which the KURSK happened to be in August 2000, could play an additional negative role in the disaster.
As the authors of this analysis see it, some more detailed geophysical studies would be in order in this region of about 2,000 km 2 . What is needed in the first place is a benthic gravimetric survey on a bigger scale with intervals of 200 m between control points which will help specify the parameters of the local high-amplitude anomaly. As for the increased levels of heavy carbohydrates, they are responsible for higher heat flow in bottom sediments. For an assessment of the vertical and horizontal components it would pay to carry out there a detailed geothermal survey (heat-field measurements).
In the scientists' opinion, an automated monitoring system should be set up in the region of the Barents Sea under investigation in order to be able to prognosticate changes in the geodynamic environment in the areas of naval exercises and operations of the coastal services with a view to increasing their safety.
Razvedka i okhrana nedr (Geological Prospecting and Conservation of Mineral Resources), No. 2, 2001
Prepared by Emma SOLOMATINA
Опубликовано 08 сентября 2018 года
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