EARTHQUAKES FELT in the NORTH CAUCASUS in 2018: ZAMANKUL EARTHQUAKE on APRIL 12, 2018 with KR=8.9, I0=4 and YANDARE EARTHQUAKE on OCTOBER 17, 2018 with KR=11.7, I0=5–6

Abstract

The article provides the instrumental and macroseismic data of two perceptible earthquakes which occurred in 2018 on the territory of the North Caucasus republics – Zamankul earthquake with KR=8.9 in North Ossetia-Alania and Yandare earthquake with KR=11.7 in Ingushetia. The tectonic situation at the sites of the foci of these seismic events was also taken into account. Zamankul earthquake was felt in five settlements with an intensity from 2 to 3–4 points despite its relatively low energy class. The intensity at its epicenter is estimated as I0=4. According to the results of the macroseismic survey of Yandare earthquake, a map of its impact in 22 settlements is built. The data are approximated by isoseists of Ii=2, 3, 4, 5. The intensity in the epicenter is estimated as I0=5–6. According to the focal mechanism solution, the earthquake occurred under the influence of prevailing compressive stress. The type of movement in the source is reverse fault with significant strike-slip component. Comparison of the nodal planes with the tectonics of the region made it possible to choose as the active nodal plane NP2 of southeastern strike, coinciding with the orientation of the Dattykh-Akhlov fault zone, to which the source is confined. Information on historical seismicity in the Yandare earthquake focal zone is given for the last 150 years. Geological and tectonic positions for both considered earthquakes are described.