Localization zones of ancient and historical earthquakes in Gornyi Altai

Abstract

The conducted paleoseismological and archaeoseismological studies reveal three zones of concentration of the ancient and historical earthquakes in Gorny Altai which are related to the Kurai Fault zone, Katun, and South Terekta faults. The surface ruptures are detected within the Kurai Fault zone, which were formed in the epicentral zones of the paleoearthquakes that occurred 6500, 5800, 3200, and 1300 years ago and had magnitudes Mw = 6.7–7.6. The recurrence period of the paleoearthquakes is 700 to 2600 years. The detected secondary seismogenic deformations indicate that an epicentral zone of the paleoearthquake with an age of less than 12.5 ka (Mw = 7.2–7.6, intensity I = 10–11), the traces of earthquakes and their clusters with M ≥ 5–5.5 and I ≥ 6–7, which occurred about 150 and 90 ka ago, in the intervals of 38–19 ka ago (with a recurrence period of about 2 ka), and 19–12.5 ka ago are related to the southern part of the Katun Fault. The earthquake of I ≥ 5–6 which damaged the constructions of the Chultukov Log 1 burial mound in the period from IV century B.C. to the beginning of I century A.D. is associated with the northern part of the Katun Fault. In the zone of the South Terekhta Fault, the seismogenic displacements that occurred in VII–VIII centuries A.D. (Mw = 7.4–7.7, I = 9–11) and about 16 ka ago (M ≥ 7, I = 9–10) are revealed. The latter triggered the formation of a landslide-dammed lake which was destroyed by the earthquake about 6 ka ago (M ≥ 7, I = 9–10). Secondary paleoseismic deformations of the ancient earthquakes (M ≥ 5–5.5, I ≥ 6–7) are recorded in the sediments of the Uimon Basin with an age of 100–90 ka and about 77 ka. These results should be taken into account in designing a gas pipeline in the People’s Republic of China, building infrastructure for tourism, and elaborating the seismic zoning maps for the territory of the Russian Federation.