THE CURRENT STATE OF CRUSTAL STRESSES IN THE CAUCASUS ACCORDING TO THE UNIFIED CATALOGUE OF EARTHQUAKE FOCAL MECHANISMS

The current state of crustal stresses in the Caucasus and adjacent territories has been reconstructed. Stress inversion was performed by the cataclastic analysis of earthquake focal mechanisms considered as seismological strain indicators. The data were taken from the unified catalogue of focal mechanisms of the Northern Eurasia, which was consolidated by the Laboratory of Tectonophysics of IPE RAS in the early 1990s. It contains the information from many seismological data sources of various authors who worked both in the USSR and abroad. Seismological data for the last years after the collapse of the USSR were taken from Global CMT catalogue. The study area has been quite densely covered by reconstructions of the principal stress axes. At the same time, the area of stress averaging has been considerably reduced by the iterative use of a window for stress averaging, which was gradually expanded for zones with reduced densities of earthquake epicenters. The revealed regularities of the current stress field based on the unified catalogue of focal mechanisms collected by different authors correlate with the reconstructions performed according to the Global CMT catalogue. The cataclastic analysis of displacements along fractures allowed estimating the stress magnitudes, and the crust of the study area was zoned with respect to the intensity of normalized values of the lowest and highest stresses of horizontal compression, as well as to the normalized values of shear stresses acting on the crustal basement. In all cases, the values were normalized to the rock strength. The stress parameters are presented in “Tectonic Stresses of Eurasia”. This new Internet resource created by the Laboratory of Tectonophysics on the IPE RAS website shows the stress data in different scales and levels of details.

earthquake focal mechanism, tectonic stress, principal stress axes, stress value

1. Akhmedov M.B., Shlyunkin A.V., Luk’yanov I.V., Rebetsky Yu.L., 2015. The field of modern crustal stresses on the IPE RAS site “Global Stress Map”. In: Modern tectonophysics. Methods and results. Materials of the Fourth Youth Tectonophysical Workshop (October 5–9, 2015). Vol. 1. IPE RAS, Moscow, p. 16–21 (in Russian).

2. Bird P., 1998. Testing hypotheses on plate driving mechanisms with global lithosphere models including topography, thermal structure, and faults. Journal of Geophysical Research: Solid Earth 103 (B5), 10115–10129. https://doi.org/10.1029/98jb00198.

3. Gushchenko O.I., 1981. Kinematic Method for Determining Stress Parameters and Characteristics of Their Relationships with Tectonic Movements along Discontinuities of Different Structural Levels. Brief PhD Thesis (Candidate of Geology and Mineralogy). Moscow, 21 p. (in Russian).

4. Gushchenko O.I., Mikhailova A.V., Nikitina E.S., Rebetskiy Yu.L., Lomakin A.A., Arefieva T.P., 1994a. The modern mechanism of crustal deformation in the Caucasus-Iranian seismically active region according to regional stress monitoring and tectonophysical modeling. In: Stresses in the lithosphere (global, regional, and local stresses). Abstracts of the First International Seminar. Moscow, p. 49–50 (in Russian).

5. Gushchenko O.I., Mostryukov A.O., Petrov V.A., 1990. Structure of the modern regional stress field of seismically active regions of the crust in the eastern Mediterranean mobile belt. Doklady AN SSSR 312 (4), 830–835 (in Russian).

6. Gushchenko O.I., Rebetsky Yu.L. , Mikhailova A.V., Rossanova G.V., Le Min Quoc, Fursova E.V., 1994b. The modern regionalstress field of Eurasia (from seismological data on crustal earthquake focal mechanisms). In: Stresses in the lithosphere (global, regional, and local stresses). Abstracts of the First International Seminar. Moscow, p. 50–51 (in Russian).

7. Gushchenko О.Н., Rebetsky Yu.L., Mikhailova А.А., Rossanova G.V., Lomakin А.А., Arefieva T.P., 1991. Regional stress monitoring and the crustal deformation mechanism in the Caucasus-Iran seismically active region. In: The mechanics of structure formation in the lithosphere and seismicity. IPE RAS, Moscow, p. 165-166 (in Russian).

8. Gushtchenko O.I., Rebetsky Y.L., Mikhailova A.V., Gushtchenko N.Y., Kuok L.M., Rassanova G.V., 1993. The recent regional field of stresses and the mechanism of the lithosphere deformation of seismoactive East-Asia region. Terra Nova 5 (1), 259.

9. Heidbach O., Rajabi M., Reiter K., Ziegler M., WSM Team, 2016. World Stress Map Database Release 2016. GFZ Data Services. https://doi.org/10.5880/WSM.2016.001.

10. Heidbach O., Tingay M., Barth A., Reinecker J., Kurfe D., Müller B., 2010. Global crustal stress pattern based on the World Stress Map database release 2008. Tectonophysics 482 (1–4), 3–15. https://doi.org/10.1016/j.tecto.2009.07.023.

11. López A., 2012. Andersonian and Coulomb stresses in Central Costa Rica and its fault slip tendency potential: new insights into their associated seismic hazard. Geological Society, London, Special Publications 367, 19–38. https://doi.org/10.1144/SP367.3.

12. Lund B., Townend J., 2007. Calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor. Geophysical Journal International 170 (3), 1328– 1335. https://doi.org/10.1111/j.1365-246X.2007.03468.x.

13. McKenzie D.P., 1969. The relation between fault plane solutions for earthquakes and the directions of the principal stresses. Bulletin of the Seismological Society of America 59 (2), 591–601.

14. Moeck I., Schandelmeier H., Holl H.-G., 2008. The stress regime in a Rotliegend reservoir of the Northeast German Basin. International Journal of Earth Sciences 98 (7), 1643– 1654. https://doi.org/10.1007/s00531-008-0316-1.

15. Morris A.P., Ferrill D.A., Henderson D.B., 1996. Slip tendency analysis and fault reactivation. Geology 24 (3), 275–278. https://doi.org/10.1130/0091-7613(1996)024<0275:STAAFR>2.3.CO;2.

16. Rebetskii Yu.L., 1997. Reconstruction of tectonic stresses and seismotectonic strain: Methodical fundamentals, current stress field of Southeastern Asia and Oceania. Translation (Doklady) of the Russian Academy of Science. Earth Science Sections 354 (4), 560–563.

17. Rebetsky Yu.L., 1996. I. Stress-monitoring: Issues of reconstruction methods of tectonic stresses and seismotectonic deformations. Journal of Earthquake Prediction Research 5 (4), 557–573.

18. Rebetsky Yu.L., 2003. Stress-strain State and Mechanical Properties of Natural Massifs According to the Data on the Earthquake Focal Mechanisms and Structural-Kinematic Characteristics of Fractures. PhD Thesis (Doctor of Physics and Mathematics). UIPE RAS, Moscow, 455 p. (in Russian).

19. Rebetsky Yu.L., Kuzikov S.I., 2016. Active faults of the northern Tien Shan: tectonophysical zoning of seismic risk. Russian Geology and Geophysics 57 (6), 967–983. https://doi.org/10.1016/j.rgg.2016.05.004.

20. Rebetsky Yu.L., Mikhailova A.V, Rosanova G.V, Fursova E.V., 1997. II. Stress-monitoring: The modern field of regional stresses in South-East Asia and Oceania. Principles of quasiplastic deforming of fractured media. Journal of Earthquake Prediction Research 6 (1), 11–36.

21. Rebetskiy Yu.L., Sim L.A., Marinin A.V., 2017. From slickensides to tectonic stresses. Methods and algorithms. GEOS, Moscow, 234 c. (in Russian).

22. Steinberger B., Schmeling H., Marquart G., 2001. Large-scale lithospheric stress field and topography induced by global mantle circulation. Earth and Planetary Science Letters 186 (1), 75–91. https://doi.org/10.1016/S0012-821X(01)00229-1.

23. Tutu A.O., Steinberger B., Sobolev S.V., Rogozhina I., Popov A.A., 2018. Effects of upper mantle heterogeneities on lithospheric stress field and dynamic topography. Solid Earth 9 (3), 649–668. https://doi.org/10.5194/se-9-649-2018.

24. Yetirmishli G.J., Kazimova S.E., 2017. Types of tectonic movements of the seismogenic areas of Azerbaijan based on the earthquake focal zones. Geological-geophysical studies of the deep structure of the Caucasus. In: Geology and Geophysics of Caucasus. Vladikavkaz, p. 20–25.

25. Yetirmishli G.J., Kazimova S.E., 2018. Focal mechanisms of earthquakes and stress field of the earth crust in Azerbaijan. In: D’Amico S. (Ed.), Moment tensor solutions: a useful tool for seismotectonics. Springer, Cham, p. 481–495. https://doi.org/10.1007/978-3-319-77359-9_21.

26. Zoback M.L., 1992. First‐and second‐order patterns of stress in the lithosphere: The World Stress Map Project. Journal of Geophysical Research: Solid Earth 97 (B8), 11, 703–11728. https://doi.org/10.1029/92JB00132.