Possible origin of the deep earthquake of October 15, 2018 in the Sea of Azov

L.O. Shumlyanskaya¹, V.Yu. Burmin², P.I. Pigulevsky¹, O.A. Gerasymenko¹

¹ Institute of Geophysics by S.I. Subbotin name, National Academy of Sciences of Ukraine

² Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

Corresponding author: V.Yu. Burmin, e-mail: burmin@ifz.ru

Abstract. Earthquakes in the Sea of Azov are quite commonplace. Until now, the idea of their nature has focused on tectonic processes in the earth's crust. In our work, using morphotectonic analysis, we examined the geodynamic situation in the collision area of the East Black Sea plate and the outskirts of the East European platform on a lithosphere scale, in order to show that not only in the earth's crust, but also in the lower part of the lithosphere there are necessary tectonic prerequisites for the accumulation of seismic energy with subsequent discharge in the form of earthquakes. Using the example of an earthquake that occurred on October 15, 2018 in the Sea of Azov, we showed possible causes of its occurrence for two options for solving the seismological problem obtained by the Geophysical Service of the Russian Academy of Sciences and entering the solution according to the method of V.Yu. Burmin. The following focal parameters are published on the Geophysical Survey website: latitude – 46.36, longitude – 37.18, depth – 5 km, m_b=4.3. For the solution using the Burmin method, the focal parameters were obtained: latitude – 46.42564, longitude – 37.24274, H=133.4 km. Mechanisms of two solutions were constructed; for the source with a depth of 5 km, the source mechanism was obtained - reverse fault, the source is confined to the intersection of Kalmius-Dzhiginsky and the Main Azov faults; for 133.4 km - fault-shift, the source is confined to the intersection of the Gubkinsky-Central Azov, Kalmius-Dzhiginsky and the Main Azov faults. The constructed model of the collision of the continental lithosphere of the East European platform and the subducting plate of the East Black Sea plate shows that under the conditions of weak compressive forces from the side of the Arabian indenter, a pseudo-subduction situation is formed, as a result of which shear stresses occur in the deformable frontal part of the continental lithosphere of the East European platform, passing throwing up along the line of cleavage. During this process, seismic energy is accumulated, accompanied by weak and moderate earthquakes, of a fault type for the earth's crust in the region of the Azov shaft, and a fault type in the lower part of the wedge of the continental lithosphere as a result of its destruction. Regional morphotectonic analysis did not allow us to choose the most probable mechanism of the earthquake source. But it should be noted that the results of our studies have shown that the occurrence of deep earthquakes has all the necessary tectonic prerequisites, despite the well-established opinion of seismologists about the exclusively crustal location of earthquakes in this region.

Keywords: earthquake, earthquake hypocentre, lithosphere, Sea of Azov, morphotectonic analysis

About the authors

SHUMLYANSKAYA Lyudmila Aleksandrovna – Ph. D. in Geological Sciences, Scientific Reseacher, Institute of Geophysics by S.I. Subbotin name of NAS of Ukraine. Ukraine, 03860, Kiev, Palladina Avenue 32. E-mail: lashum@ukr.net

BURMIN Valerii Yurievich – Doctor of Physical and Mathematical Sciences, Chief Researcher, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. 123242, Moscow, ul. Bolshaya Gruzinskaya 10, building 1. E-mail: burmin@ifz.ru

PIGULEVSKY Petro Ignatievych – Doctor of Geological Sciences, Senior Researcher, Institute of Geophysics by S.I. Subbotin name of NAS of Ukraine. Ukraine, 03860, Kiev, Palladina Avenue 32.
E-mail: pigulev@ua.fm

GERASIMENKO Olga Alekseevna – Ph. D. in Geological Sciences, Research Fellow, Institute of Geophysics by S.I. Subbotin name of NAS of Ukraine. Ukraine, 03860, Kiev, Palladina Avenue 32.
E-mail: olaginko@gmail.com

Cite this article as: Shumlyanskaya L.O., Burmin V.Yu., Pigulevsky P.I., Gerasymenko O.A. Possible origin of the deep earthquake of October 15, 2018 in the Sea of Azov, Seismicheskie Pribory, 2020, vol. 56, no. 1, pp. 32–43. (in Russian). https://doi.org/10.21455/si2020.1-3

English translation of the article will be published in Seismic Instruments, ISSN: 0747-9239 (Print) 1934-7871 (Online), https://link.springer.com/journal/11990), 2020, Volume 56, Issue 5.