STRESS STATE OF UZBEKISTAN’S SEISMOACTIVE AREAS
Yu.L. Rebetsky1, T.L. Ibragimova2, R.S. Ibragimov2, M.A. Mirzaev2
1.Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
2. Mavlyanov Institute of Seismology, Academy of Sciences of Republic of Uzbekistan, Tashkent, Uzbekistan
Corresponding author: Yu.L. Rebetsky, e-mail: reb@ifz.ru
Abstract. The study of the current stress state of the Earth’s crust of the Uzbekistan territory was carried out by methods of cataclastic analysis of displacements along fault sets for the collected catalogue of earthquake focus mechanisms (EFM), compiled according to the data of various authors. Two stages of stress field reconstruction are implemented at different levels of area detail of averaging parameters and at different magnitude hierarchy of analyzed earthquakes. Azimuths and dip angles of principal stresses axes, Lode – Nadai coefficient values, geodynamic type of stress state, relative (normalized for cohesion strength of rock massif) normalize values of maximum shear stress and effective pressure are determined for different areas of studied territory. As a result of natural stress reconstructions were revealed based on the focal mechanisms of earthquakes with magnitudes M ≤ 4.5 and M ≥ 5 differences in the parameters of the stressed state carried out. It has been suggested that the hierarchy of magnitude levels of the considered earthquakes reflects the stressed state of various deep layers of the Earth’s crust. It is shown that strong earthquakes gravitate to zones of reduced effective pressure. On this basis, segments of active faults are identified in the territory of Eastern Uzbekistan, which are considered as zones of potentially increased seismic danger.
Keywords: earthquake focal mechanism, reconstruction of the stress field, principal stress axes, stress ellipsoid, geodynamic type of stress state
About the authors
REBETSKY Yuriy Leonidovich – Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. Russia, 123242, Moscow, Bolshaya Gruzinskaya st., 10-1. E-mail: reb@ifz.ru
IBRAGIMOVA Tatyana Ludvigovna – Mavlyanov Institute of Seismology, Academy of Sciences of Republic of Uzbekistan. Uzbekistan, 100128, Tashkent, Zulfiyakhonim str., 3. E-mail: tam.anay@yahoo.com
IBRAGIMOV Roman Solomonovich – Mavlyanov Institute of Seismology, Academy of Sciences of Republic of Uzbekistan. Uzbekistan, 100128, Tashkent, Zulfiyakhonim str., 3. E-mail: ibrroma@yandex.ru
MIRZAEV Murodjon Abdurahimgjanovich – Mavlyanov Institute of Seismology, Academy of Sciences of Republic of Uzbekistan. Uzbekistan, 100128, Tashkent, Zulfiyakhonim str., 3. E-mail: mumirzaev@gmail.com
Cite this article as: Rebetsky Yu.L., Ibragimova T.L., Ibragimov R.S., Mirzaev M.A. Stress state of Uzbekistan’s seismoactive areas, Voprosy Inzhenernoi Seismologii (Problems of Engineering Seismology). 2020. V. 47, No. 3. P. 28–52. [in Russian]. https://doi.org/10.21455/VIS2020.3-2
English translation of the article will be published in Seismic Instruments, ISSN: 0747-9239 (Print) 1934-7871 (Online), https://link.springer.com/journal/11990