Spatial Distribution of Crustal Earthquakes in the Caucasus

Burmin, V. Yu.; Shemeleva, I. B.; Fleyfel, L. D.; Avetisyan, A. M.; Kazaryan, K. S.

doi:10.3103/s0747923919010043

Cited by 15 publications

(4 citation statements)

References 3 publications

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“…It experiences a differential nature of uplift and mountain building (Adamia et al, 2011). Areas of increased seismic activity are characterized by the presence of highly magnetic crystalline rocks and a variety of structures of electrotelluric fields (Burmin et al, 2019;Lukk and Shevchenko, 2019).…”

Section: Study Areamentioning

confidence: 99%

Local Variations of the Geomagnetic Field Components as Possible Precursors of the Paravan and Spitak Earthquakes

Grigorian

Баранов

2022

Preprint

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We analyze variable geomagnetic field δΤ which characterizes the change in electrical conductivity in the Earth's crust for the Armenia from 1986 to 1993. Clear geomagnetic precursors of the Paravan (13.05.1986, М=5.4) and Spitak (07.12.1988, М=7.0) earthquakes are obtained. About half a year before the Spitak earthquake, the parameters of the ratios of bay-like variations (30–60 and 5–25 min) of the horizontal and vertical components of the geomagnetic field δΤ decreased by about 30%. An analysis of the data two months before the Paravan earthquake also shows a sharp drop in the values of this parameter by 20–25%. In the interval between two earthquakes, the ratios of bay-like variations lie in the range of ± 10% with an average value of 1. For the Sq variations of the δD, δH, and δZ components of the geomagnetic field δΤ, a sharp drop was observed about a month before the Paravan earthquake from 1.2 to 0.8. After the Paravan earthquake, all three components partially returned to their pre-earthquake parameters (~ 1.2) within a few months. Further, a monotonous decrease in all three components of the geomagnetic field was observed up to the Spitak earthquake from 1.2 to 0.54. After this earthquake, the bay-like and Sq variations returned to normal values between 1 and 1.2 within a few months. The difference in the behavior for the bay-like and Sq variations in the period between two earthquakes is possibly associated with the beginning of the preparation of the Spitak earthquake a few months after the Paravan earthquake.

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Section: Study Areamentioning

confidence: 99%

Local Variations of the Geomagnetic Field Components as Possible Precursors of the Paravan and Spitak Earthquakes

Grigorian

Баранов

2022

Preprint

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“…Let us now illustrate the ambiguity in determining the depth of hypocenters of earthquakes with real data. Let us consider several earthquakes that, according to the seismological catalog, are located in the earth's crust, but according to the data of [Burmin, Shumlianska, 2015, 2018aBurmin et al, 2019] are defined as mantle's earthquakes. For the earthquakes that occurred on 17.03.2011 the experimental travel-time curves are presented in Fig.…”

Section: Mantle Earthquakes In the Crimea-black Sea-caucasus Regionsmentioning

confidence: 99%

“…Seismological stations recording the earthquakes of the Caucasus are located on the territory of several states: Russia, Armenia, Georgia, Azerbaijan, Iran and Turkey. The velocity model is taken from the article devoted to the recalculation of the hypocenters of the Caucasus [Burmin et al, 2019].…”

Section: Mantle Earthquakes In the Crimea-black Sea-caucasus Regionsmentioning

confidence: 99%

“…Points obtained from the data on the foci after recalculation (Fig.8, b) are located along the line of the theoretical hodograph for a depth of 130 km.Seismological stations recording the earthquakes of the Caucasus are located on the territory of several states: Russia, Armenia, Georgia, Azerbaijan, Iran and Turkey. The velocity model is taken from the article devoted to the recalculation of the hypocenters of the Caucasus[Burmin et al, 2019].Fig.9shows the points of the hodograph for the earthquake occurred on 18.07.1997.…”

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Mantle earthquakes in the Crimea-Black Sea-Caucasus regions

Burmin

Kendzera

Shumlianska

et al. 2021

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The question of the existence of foci of deep earthquakes in the region of the Crimea-Black Sea-Caucasus is extremely important from the point of view of the geodynamics of the region. Previously it was thought that only crustal earthquakes could occur in this region. Recently, results have been obtained that show that earthquakes with depths of at least 300 km occur in this region. The article discusses the question of how plausible these results are and why they were not obtained earlier. Seven specific examples of the ambiguous determination of the depth of earthquake hypocenters in the Crimea-Black Sea-Caucasus region are considered. These examples clearly show that determining the coordinates of earthquake hypocenters using algorithms based on the Geiger method does not allow one to uniquely determine the depth of the hypocenters. The article gives an idea of the authors about the origin of mantle earthquakes in the Caucasian and Crimean-Black Sea regions. For the Caucasus region, mantle earthquakes are associated with two reasons: submersion of the lithospheric layer; in the asthenospheric layer, represented in the seismotomographic sections by a low-velocity anomaly, the nature of earthquake foci is associated with fluids formed during phase transition reactions. In the Crimean-Black Sea region, earthquake foci are located in the lithosphere layer, and the sliding of the lithosphere along the less viscous underlying layer of the upper mantle causes tectonic movements in the lithosphere accompanied by earthquakes. In addition, to determine the coordinates of the hypocenters of the Crimean and Caucasian earthquakes during routine processing, hodographs were used for depths not exceeding 35 km for the Crimea and 50 km for the Caucasus and 150 for the North Caucasus. This circumstance is the main reason why deep earthquakes could not be detected.

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