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Information message on the earthquake October 19, 1999 happened near Stavropol town

Information message on the earthquake October 19, 1999 happened near Stavropol town.

Preliminary processing has been done with data from 6 stations, accurate processing - with data 11 stations.

Figure 1 carries records from digital stations KIV, OBN, ARU, obtained by IPC in a close to real time mode. On record from KIV station one can see not only main strike but aftershock too, which happened in 7 minutes. According to data of Kavminvod test area's local network by October 21 two aftershocks have been registered on October 19 at 18:25 and on October 20 at 19:59 (GMT) with energy classes 8-8.5. Records for the first aftershock registered on five survey points located at distances 30-125 km from hypocenter are presented in figure 2.

Figure 1

Figure 2

IPC GS RAS also has obtained information with parameters of this event from some seismological centers, these data are given in table 1:

Table 1

NN	Time in origin h-min-s (GMT)	Lat degr.	Lon degr.	Depth km	N s/st	Ms/ N	mb/ N	I0 calc	GAP	Center
1	18-18-43.60	44	43	33	6	4.10/4		3.5-4		IPC GS RAS (preliminary)
2	18:18:44.6	45	42	33	12	4.1/5		3-4		IPC GS RAS (improved)
3	18:18:44.11	45	42		8	4.4/4	4.1/4			pIDC
4	18:18:46.4	44	42	12	12	4.2/4		5-5.5		DRIPC

IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences

pIDC - Prototype International Data Center

DRIPC - Regional Informational Processing Center of Dagestan Experimental-Methodical Seismological Department Geophysical Survey Russian Academy of Sciences

Epicenter

Station data from regional stations of Northern Caucasus and survey points of local network in Kavminvod geodynamics test area are presented in table 2.

Table 2

Code stations	Delta	Az	Phase	Time			Phase	Time
Code stations	km	degr.	Phase	hh	mm	ss	Phase	mm	ss
NAG	31.9	163.3	iPg	18	18	52.78	eSg	18	57.46
GOF	49.3	34.1	iPg	18	18	53.50	eSg	18	63.00
BUG	78.6	171.3	ePg	18	18	59.67	eSg	19	10.51
PYA	82.0	157.7	iPg	18	19	0.00	iSg	19	11.50
KIV	84.2	178.7	ePg	18	19	0.66	eSg	19	12.39
KII	84.6	179.0	ePg	18	19	0.50
GUM	110.3	197.2	ePg	18	19	4.55	eSg	19	19.95
KUB	115.9	148.3	IPg	18	19	6.90
SOC	267.7	242.0	iPn	18	19	27.00	eSn	19	57.00
ANN	414.3	271.3	ePn	18	19	44.50	iSn	20	31.00
MAK	435.7	116.8	iPn	18	19	47.80	iSn	20	57.00

Macroseismic manifestations

The earthquake has been felt in village Gofitskoe of Stavropol Region with intensity of 3-4 MSK, in Stavropol town with intensity 3 MSK, in Piatigorsk town with intensity 2 MSK. Regional department of Ministry of Accidental Situations has announced that this earthquake was felt in a number of places: In village Novy Akul of Andropovsky region the strong howl has been heard for 10-15 min, dogs barked and gooses were worried. In the local school and central heating station plaster has been falling out of cracks in concrete plates. On Maisky Farm (15 km to the North from village Novy Akul of Andropovsky region) in many houses the bricks have been falling out from walls.

Historical records

Region of Stavropol heights is the only place within the Skiff plate area, where appreciable events happened earlier and take place today. The first one of them is Stavropol earthquake in 1827 with intensity 6-7 MSK (M=4.6); three 7 MSK earthquakes - Vorovskolessk with M=4.1, Vladimir with M=3.5 and Nevinnomisk with M=3.8 happened in 1895, 1947 and 1963 respectively, and at last the second Stavropol earthquake in 1971 with M=4.5, which was felt on the earth's surface with intensity of 8 MSK. Parameters of these events are given in table 3.

Table 3

Data			Time, hhmmss	Coordinates		Depth, km	Ms	Io, MSK
Year	Month	Day	Time, hhmmss	N, degr.	E, degr.	Depth, km	Ms	Io, MSK
1827	10	21	.0	45.00	42.50	15	4.6	6-7
1895	11	05	03±1h	44.40	42.40	2	3.1	6-7
1947	11	23	053716.0	45.30	43.20	3	3.5	7
1963	12	25	132516.0	44.60	42.40	3	3.8	7
1971	10	02	105641.0	44.80	42.10	2	4.5	8