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Information message about the strong earthquake near the Southern Greece coast on February 14, 2008

The strong earthquake with M=6.7 has occurred on February14, 2008 at 10:09 GMT (13:09 Moscow time) near the South Greece coast.

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 this earthquake has been delivered in 26 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).

Preliminary processing has been done with data from 44 stations, accurate processing - with data 50 stations.

Fig. 1 presents fragments of records obtained from digital stations Isparta (∆ 7º), Kasperske Hory (∆ 13.7º), Kislovodsk (∆ 17.4º), Garni (∆ 18.2º), Obninsk (∆ 20.9º), Vasula (∆ 21.9º). Fig. 2 presents fragments of records obtained from digital stations Arti (∆ 31.4º), Borovoe (∆ 37.2º), Kurchatov (∆ 42.3º), Tiksi (∆ 60.6º), Yakutsk (∆ 65.8º), Bilibino (∆ 72.1º).

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	10-09-22.8	36.81	21.84	33	50	6.7/24	6.5/26	7.5-8	206	IPC GS RAS (Accurate)
2	10-09-22.8	36.79	21.85	33	44	6.7/20	6.6/22	7.5-8	206	IPC GS RAS (Preliminary)
3	10-09-21.4	36.57	21.73	30	457	7.0Mw			30	CSEM
4	10-09-23.6	36	21	30	180	6.7Mw	6.2/172		50	NEIC

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

CSEM - European - Mediterranean seismological center

NEIC - National Earthquakes Information Center of US Geological Service

Epicenter

Fig.3 downloaded from the US Geological Service NEIC depicts epicenter of this earthquake, which was located in the sea near the South Greece coast in 55 km to the south-south-west from Kalamata and in 230 km to the south-west from Athens.

Figure 3

Aftershock

3 aftershocks have been registered by GS RAS within 7 hours after the main shock:

N	Date & Time (GMT) yy-mm-dd hh:mm:sec	Lat degr.	Lon degr.	Depth km	N station	Ms/ N	mb/ N	Io calc.	Region
20080474	2008-02-14 10:36:14.0	36.31	21.71	33	11	-	4.6/ 7	2.5-3	Southern Greece
20080475	2008-02-14 12:08:55.0	36.55	21.93	33	44	6.1/ 23	6.4/ 25	6.5-7	Southern Greece
20080477	2008-02-14 17:26:41.0	36.46	21.56	33	18	-	5.1/ 12	3.5-4	Southern Greece

Historical records

The earthquake on has occurred on February 14 near Peloponnesus Peninsula in the southern part of Greece. This is extremely seismic active region of Mediterranean Sea which belongs to Alpine - Himalayan tectonics belt. This idea is proved by the map of seismic activity downloaded from of European Mediterranean Seismological Center EMSC-CSEM – fig.4. It presents epicenters of the earthquakes registered within instrumental period of survey since 1964 till 2002 and taken from catalogue International Seismological Center. The strongest and most famous earthquakes of this region which were accompanied with victims and destructions are presented in the table (fig. 5 - source EMSC-CSEM, and T. Utsu ; International Handbook of Earthquake and Engineering Seismology; vol. A; 691-718). The significant seismic activity at the Peloponnesus Peninsula in accordance with National Observatory in Athens and the Department of Geophysics of Aristotil University in Saloniki has begun in January, when on January 6 the earthquake with ML=6.5 and the depth of 82 km. has been registered in the western part of peninsula and was accompanied with weak shocks, which were also deep under the surface (fig.6). Rather moderate earthquakes also have happened on January 31, February 1 and 2 in the south-eastern coastal part – near Kitira Island. The series of earthquakes have been registered of February4 at the north-western part of Peninsula with ML=5.6-4.0. They had the crust depths of the origins. Possibly the locations of these origins are not accidental and determine the dimension of seismic tectonic block, the strength in which has reached the apogee.

Figure 4	Figure 5

Figure 6

Focal mechanism and seismic moment of the earthquake

Focal mechanism solutions for this earthquake 14.02.2008 were obtained in various seismological centers and they are presented on fig. 7 (from European Mediterranean Seismological Center EMSC -CSEM. Here: HRVD – Harvard Center, USA; USGS – National Center of Information about the earthquakes, USA; INGV – Italian National Seismic Network, Италия; UPSL – Geophysics Department, Uppsala University, Sweden; AUTH – Seismological Institute, National Observatory of Athens Greece, KAN – Kandilli Observatory and Earthquake Research Institute (KOERI). All solutions are rather close. Elements of focal mechanism of the earthquake14.02.2008 were obtained in GS RAS from initial signs P-wave arrivals for the model of twin pair of forces and calculated with the method of moment tensor centroid in Harvard Center, USA (HARVARD), they are presented in table 2. This earthquake has happened under the action of almost equal compression and expansion forces, oriented to the north-east– south-west. The motion along the flat nodal plane was to the north-western direction and characterized by the thrust (with components of right side shift), the motion along the steep falling plane was directed to the south-east and characterized by uplift. Seismic moment Мо of the earthquake 14.02.2008 was determined in GS RAS from Р-wave spectra registered by digital IRIS equipment of seismic station Arti (ARU) located at the distance of 31 degrees. The value Мо made 2.0* 10** 19 n*m. The value of moment magnitude Mw was calculated from Kanomori formula and made Мw=6.8. The value of seismic moment Мо of the earthquake 14.02.2008 in accordance with HRVD data made 2.7* 10** 19 n*m, the value of moment magnitude - Mw = 6.9.

Table 2

Axes of main strengths						Nodal planes						Center
T		P		N		NP1			NP2
Pl	Azm	Pl	Azm	Pl	Azm	Stk	Dp	Slip	Stk	Dp	Slip
48	10	36	225	18	121	11	19	161	119	84	72	IPC GS RAS
50	31	40	216	3	124	331	6	117	124	85	87	HARVARD

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

HARVARD - Harvard Geophysical Center (USA)

Figure 7