The NSU geologists, working in the Institute of Petroleum Geology and Geophysics and the Institute of Geology and Mineralogy of Siberian Branch of the Russian Academy of Science, have found the traces of previously unknown ancient major earthquakes in Gorny Altai. The findings made them reconsider the seismic hazard in some areas of Gorny Altai, where strong earthquakes were not registered before. It is also important to take this fact into account when constructing facilities and a gas pipeline to China called "The Power of Siberia-2".
The research has been carried out by E.V. Deev (NSU, the Institute of Petroleum Geology and Geophysics of Siberian Branch of the Russian Academy of Science) and J. D. Zolnikov (NSU, the Institute of Geology and Mineralogy of Siberian Branch of the Russian Academy of Science). The results have been published in the "Geology and Geophysics" journal.
The NSU press service has obtained the detailed information from Evgeny Deev, the candidate of geological-mineralogical sciences, associate professor of geological and geophysical faculty of NSU, a senior researcher at the Laboratory of Geodynamics and Paleomagnetism located in the Institute of Petroleum Geology and Geophysics of Siberian Branch of the Russian Academy of Science.- We are engaged in palaeoseismological research in Gorny Altai and the northern Tien Shan. The reconstruction of ancient earthquakes occured in these areas is extremely important not only scientifically, but also from a practical point of view, since it allows to specify the potential seismic hazard areas and take it into account when constructing various objects. Unfortunately, the available tools and historical data about the earthquakes occured in these regions cover a short period. The instrumental seismological observations are being held here only for last 50-60 years, and historical sources allow to delve no more than 200-250 years ago, - Eugene Deev says.
Paleoseismologists reconstruct the ancient earthquakes studying the deformation left by the earthquakes in the terrain and sediments. They explore fractured ledges, ditches, landslides and avalanches caused by earthquakes, as well as secondary deformation appeared due to the effects of soil liquefaction. A study of the ancient earthquakes’ impact on archaeological sites also provides the interesting data about ancient earthquakes themselves. As a result, the scientists can determine the magnitude, intensity, position of the epicentral area and the age of an ancient earthquake.
The strongest Chui earthquake happened in 2003 with the intensity of 8-9 points caused the interest in studying the ancient earthquakes on the territory of Gorny Altai. Nowadays, the tourist facilities are being actively constructed in the regions of the Gorny Altai studied by paleoseismologists. There are plans not only for the construction of small hydro power stations, but also for laying a gas pipeline to China. So, to understand the nature of the ancient seismic processes happened in these regions is especially important now.
The Novosibirsk geologists have summarized the data of their palaeoseismological research of Yaloman graben located in Gorny Altai. It is assumed to lay a gas pipeline called “The Power of Siberia-2” on the right bank of the Katun river.- We have recorded the several levels of seismogenic deformations appeared due to the effect of soil liquefaction during the strong ancient earthquakes. The minimum earthquake’s magnitude, necessary for the formation of these tracks, is 5-6 points. We have been able to trace the most impressive paleoearthquake with the intensity of about 8 points at a distance of 10 km, - Eugene Deev says.
The researchers have not been succeeded yet to find out the exact position of the earthquake’s epicenter. However, the scientists have been able to determine the age of this event. The radiocarbon dating of the bone fragments of a red deer and Siberian ibex showed that the earthquake occurred about 10,500 years ago. Such strong earthquakes were not registered in this area before.-'' The obtained data and our investigations made before allowed us to suggest that there were strong earthquakes with a magnitude of 5-7 points happened many times in the area of Yaloman graben in the ancient times. The last of such earthquakes was with the greatest magnitude. The seismic deformation found near Yaloman graben and also the palaeoseismological and archeoseismological data of Manzherok graben and Chemal graben (the area of the lower current of the Katun river) showed that numerous strong ancient earthquakes could be concerned with the length of Katun fault (it’s length is about 200 km). Therefore, the Katun River Valley and the surrounding mountain ranges, characterized by a few seismic events with low magnitudes have much more significant seismic potential. This should be taken into account when assessing the seismic hazard in the region, designing a line of the pipeline to China and constructing the tourist facilities, - the scientist says.
Photos provided by Eugene Deyev