O. P. Smekalin

Paleoearthquakes in the Baikal region: Methods and results of timing

Over the half-century history of seismological studies in the Baikal region, more than 70 seismotectonic or inferred seismic dislocations related to displacements along active faults have been established. Some of them have been studied in detail by trenching and methods of absolute and relative timing. The current work discusses the age of paleoearthquakes in the Baikal region and gives an overview of modern methods of dating of related dislocations.

Paleoseismicity of the Pribaikalie

Results of paleoseismogeological investigations, including trenching carried out over 20 years, are shown. Absolute 14C dates of buried soils and a list of paleoseismic dislocations and paleoevents dated by different methods are also given. Unexpected results obtained for the paleoearthquake magnitude and kinematics of dislocations are discussed.

Paleoseismological investigations in the pleistoseismal zone of the 1885 Belovodskoe earthquake, North Tien Shan

The results of paleoseismological investigations to find the epicentral area of the Belovodskoe earthquake are presented. New data on prehistoric earthquakes have been obtained resulting from a seismic deformation study using trenching. It is found that seismic dislocations during the reactivation of the fault by the 1885 earthquake did not extend east of the Sokuluk River. In addition, the age and kinematic features of a paleoearthquake located in the area between the Sokuluk and Alamedin rivers are specified. This earthquake occurred in the interval of 887–1533 cal BC and was no less than 7.1 in magnitude. The minimal estimated earthquake source length is 32 km and the reverse-fault amplitude is 3.8 m.

Paleoseismic dislocations in the Klichka thrust zone, southeastern Transbaikalia

The results of the field seismogeological studies in the Klichka thrust zone, southeastern Transbaikalia, are considered in this paper. This territory in the contemporary epicentral field is characterized by weak earthquakes that do not reflect the true seismic potential. The seismotectonic dislocations, corresponding in their parameters to fault-forming earthquakes with magnitude of 6.0–7.2, are revealed in the southwestern flank of the Klichka thrust. Radiocarbon dating of the paleoevents and historical-archaeological data indicate that the age of the oldest events registered during the field works is 9300 years ago (M = 7.2). An earthquake with M ≈ 6.5 occurred 7000 years later, sometime in the 1st to 11th centuries. The third paleoearthquake with M ≈ 6.0 occurred in the 12th to 18th centuries.

Outlook for use of laser scanning in paleoseismological studies in Siberia

A large-scale survey to select a path for the East Siberia-Pacific Ocean (ESPO) pipeline has shown the urgency and high demand for detailed paleoseismological investigations using a new technology based on laser scanning. The laser scanning results allowed us not only to identify and thoroughly map numerous fault-line scarps, but also to estimate their morphometric parameters (height, steepness) and distinguish scarps that were formed as a result of single or multifold seismogenic displacements. The high efficiency of the laser scanning results makes it necessary to involve this tool in paleoseismological investigations.

Paleoseismological Investigation of the Kichera Fault Zone in the Northern Baikal Region

In the recent structure of the Baikal Rift Zone, the Kichera Fault serves as the northwestern boundary of the Angara-Kichera aggradation depression. A seismotectonic scarp 60 m high was formed as a result of normal faulting during the late Pleistocene and Holocene. The erosion-aggradation and seismic landforms testify to the nonuniform growth of this scarp. To study the character of the seismic activity in the Kichera Fault Zone, we excavated two trenches across the seismotectonic scarp. The Holocene stage of the seismotectonic activation within the fault zone and the preceding period of relative quiescence were outlined from the character of the deformations in the trench sections and previous geomorphic investigations. According to our preliminary estimations, the active stage that started at the end of the late Pleistocene and that has remained incomplete until now was accompanied by at least three rupture-forming earthquakes.

Seismotectonic investigations of the Chulmakan fault, southern Yakutia, to assess the seismic hazard for the East Siberia–Pacific Ocean oil and power of Siberia gas pipelines

Based on the analysis of space images and maps, the data of laser scanning, trenching, and field geophysical and seismotectonic studies in southern Yakutia, the Chulmakan seismogenic fault is mapped and characterized. The structure and parameters of seismogenic deformations of this fault, which crosses the Power of Siberia gas pipeline, are determined. A preliminary estimate of the Chulmakan seismodislocation age is given, as well as the magnitude of the corresponding paleoearthquake. The level of potential seismic hazard at the site where the Chulmakan Fault crosses the East Siberia–Pacific Ocean oil pipeline and Power of Siberia gas pipeline is determined.