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Information message on felt earthquakes in Chechnya on December 12 and 13, 2020

The felt earthquake with М=4.7 has occurred on December 12, 2020 at 21:29 GMT (December 13, 00:29 Moscow time) in Chechnya (moderate in the epicenter on the ShSI-17 scale) . Another shock with М=4.8 (moderate in the epicenter on the ShSI-17 scale) has been registered in 13:55 minutes after it on December 13, 2020 at 11:34 GMT (14:34 Moscow time).

Parameters of the earthquake have been determined in the Alert Service (AS) of Information Processing Center (IPC) of Geophysical Survey of RAS in Obninsk with station data obtained from digital and analog seismic stations of Russia, countries of CIS and from abroad. Alert message on the first earthquake has been delivered in 23 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM). Alert message on the second earthquake has been delivered in 19 min.

Preliminary processing for the first earthquake has been done with data from 11 stations, accurate processing - with data from 46. Preliminary processing for the second earthquake has been done with data from 11 stations, accurate processing - with data from 46.

The red markers on the map present epicenters of the earthquakes which origins were located on the territory of Chechnya, at the depth of 10 km, the first origin was 5 km SWу of Urus-Martan, 18 km W of Chiri-Yurta and 28 km SW of Grozny. EPicenter of the second shock was 5 km NW of the first one.

	Time in origin (GMT)	Latitude, degree	Longitude, degree	Depth, km	Stations number	Ms/N	mb/N	I0 (calculated)	GAP	Center
1	21:29:50.0	43.08	45.52	10.0	46		4.7/27	5-6	62	GS RAS(Verified [1]) Federal research center, Geophysical survey of Russian Academy of Sciences
2	21:29:50.6	43.56	45.58	10.0	11		5.0/10	5-5.5		GS RAS(Preliminary [1]) Federal research center, Geophysical survey of Russian Academy of Sciences
3	21:29:48.6	43.04	45.54	19.7	50	4.9			87	RCNC GS RAS (Verified [1]) Regional center for the North Caucasus
4	21:29:51.0	43.23	45.67	20.0	343		4.7/58		23	CSEM(Verified [1]) European - Mediterranean seismological center
5	21:29:51.4	43.21	45.52	25.0	92		4.7/90		43	NEIC(Verified [1]) National Earthquakes Information Center of US Geological Service
6	11:34:19.0	43.12	45.49	10.0	42		4.8/6	5-6	61	GS RAS(Verified [2]) Federal research center, Geophysical survey of Russian Academy of Sciences
7	11:34:18.0	43.02	45.51	19.6	49	4.6			89	RCNC GS RAS (Verified [2]) Regional center for the North Caucasus
8	11:34:18.0	43.18	45.59	10.0	178	ML 4.6			17	CSEM(Verified [2]) European - Mediterranean seismological center
9	11:34:18.8	43.23	45.64	10.0	45		4.6/45		47	NEIC(Verified [2]) National Earthquakes Information Center of US Geological Service

Fig. 1 presents fragments of records obtained from digital stations Groznyy (∆ 0.2º), Vedeno (∆ 0.5º), Nalchik (∆ 1.5º), Neytrino (∆ 2.1º), Кисловодск (∆ 2.2º) for the first earthquake. Fig. 2 presents fragments of records obtained from digital stations Groznyy (∆ 0.2º), Vedeno (∆ 0.5º), Nalchik (∆ 1.4º), Neytrino (∆ 2º), Kislovodsk (∆ 2.2º) for the second earthquake.

Image 1

Image 2

GS RAS registered another 9 earthquakes with minor magnitudes of М>=3.2 within December 12,13 and 14. The earthquake of December 12 occurred at 23:50 and was felt in Urus-Martan and Grozny with intensity 2-3 MSK. The earthquake of December 13 occurred at 13:05 and was felt in Urus-Martan, Chechen-Aul, Grozny, Shali, Achkhoy-Martan with intensity 3 MSK.

N	Time in origin (GMT)	Latitude, degree	Longitude, degree	Depth, km	Stations number	Ms/N	mb/N	I0 (calculated)	Region
20204709	12/12/2020 23:50:22.0.0	43.09	45.55	10.0	20		4.1/12	3-3.5	Eastern Caucasus
20204715	13/12/2020 09:15:46.0.0	42.94	45.48	10.0	19		3.7/1	2-2.5	Eastern Caucasus
20204717	13/12/2020 12:08:27.1.0	43.04	45.5	10.0	22		3.8/5	2.5-3	Eastern Caucasus
20204718	13/12/2020 13:05:02.0.0	43.05	45.49	10.0	37		4.5/5	4-4.5	Eastern Caucasus
20204719	13/12/2020 13:36:43.0.0	43.11	45.52	10.0	22		3.9/4	2.5-3	Eastern Caucasus
20204723	14/12/2020 00:13:00.1.0	43.08	45.49	10.0	25		3.9/1	2.5-3	Eastern Caucasus
20204724	14/12/2020 00:37:17.0.0	43.13	45.55	10.0	20		3.5/1		Eastern Caucasus
20204725	14/12/2020 00:56:15.1.0	43.05	45.49	10.0	16		3.3/1		Eastern Caucasus
20204730	14/12/2020 08:52:45.0.0	43.0	45.51	5.0	13		3.2/4	2-2.5	Eastern Caucasus

According to GS RAS the earthquake on December 12 was felt in Urus-Martan, Chechen-Aul, Grozny, Achkhoy-Martan, Goy-Chu, Martan-Chu, Tangi-Chu, Roshni-Chu, Gekhi, Valerik, Gikalo, Starye Atagakh, Qatar-Yurt, Goyty with intensity 5 MSK, in Shali, Argun, Tsotsi-Yurt, Sernovodsky, Samashki, Assinovskaya, Avtury with intensity 4 MSK, in Makhachkala with intensity 2-3 MSK, the earthquake on December 13 was felt in Urus-Martan, Chechen-Aul, Grozny, Achkhoy-Martan, Staryh Atagah with intemsity 4 MSK, in Shali, Argun, Tsotsi-Yurt with intensity 3 MSK.

Click here to view detailed macroseismic data (DyfitWeb service)

The focal mechanism solution of the origin of the earthquake was obtained by GS RAS with signs of initial arrivals of P waves at 42 stations including 19 stations which registered compression waves (plus signs) and 23 stations which registered tensile waves (minus signs). These stations are located in the epicentral distances of 0.3-4.6º and in azymuth sector Az=34-319º. The focal mechanism solution in stereographic projection on the lower hemisphere and the elements of the mechanism are presented in the table. The earthquake occurred under the action of prevailing compressive stresses oriented E-NE (AZ=162º). One nodal plane NP1 strikes E-NE (STK=66º), another plane NP2 strikes W-SW (STK=257º), both planes are inclined to the horizon at an angle DIP=45º. The type of motion along both planes – reverse faults.
The focal mechanism solution of the origin of the second earthquake was obtained by GS RAS with signs of initial arrivals of P waves at 40 stations including 23 stations which registered compression waves (plus signs) and 17 stations which registered tensile waves (minus signs). These stations are located in the epicentral distances of 0.3-4.0º and in azymuth sector Az=43-306º. The focal mechanism solution in stereographic projection on the lower hemisphere and the elements of the mechanism are presented in the table. The earthquake occurred under the action of the prevailing compression stresses oriented to the south (AZ=41º). One nodal plane NP1 strikes W-NW (STK=298º), another plane NP2 strikes S-SE (STK=153º). The plane NP2 lies flatter (DP=31º) if compared with NP1 (DP=64º). The type of motion along both planes – reverse faults.

Axes of main strengths			Nodal planes		Center
T	P	N	NP1	NP2	Center
PI: 84 Azm: 252	PI: 0 Azm: 162	PI: 6 Azm: 72	Stk: 66 Dp: 45 Slip: 82	Stk: 257 Dp: 45 Slip: 98	GS RAS Federal research center, Geophysical survey of Russian Academy of Sciences
PI: 67 Azm: 177	PI: 17 Azm: 41	PI: 15 Azm: 306	Stk: 298 Dp: 64 Slip: 73	Stk: 153 Dp: 31 Slip: 121	GS RAS Federal research center, Geophysical survey of Russian Academy of Sciences

Quakes occurred 136-138 km W of another felt quake of May 24, 2019 in Dagestan with a magnitude of M = 4.6 and 75 km W-SW of a devastating earthquake of October 11, 2008 in Chechnya with a magnitude of M = 5.6. That earthquake in Chechnya was felt in 5 regions of the Russian Federation (Chechnya, Dagestan, Ingushetia, Ossetia and the Stavropol Region), as well as in Georgia and Armenia. The most severe destruction was in the Kurchaloy district and in Gudermes. Partial destruction was in the Shalinsky, Gudermes districts, in the cities of Grozny and Argun. The earthquake killed 13 people and injured more than 100.
A series of earthquakes occurred in the junction zone of the Vladikavkaz deep fault and the Dattykh-Akhlovskaya buried suture-shear zone.

Image 1