Information message about sensitive earthquake in Bulgaria on May 22, 2012 |
| The sensitive earthquake with M=5.7 has occurred in Bulgaria on May 22, 2012 at 00:00 GMT (04:00 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 this earthquake has been delivered in 19 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 57 stations, accurate processing - with data 66 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Apeiranthos of Naxos (∆ 6º), Isparta (∆ 7.6º), Storozhevoe (∆ 13.9º), Obninsk (∆ 15.2º), Vasula (∆ 15.9º). Fig. 2 presents fragments of records obtained from digital stations Arti (∆ 26.5º), Borovoe (∆ 32.8º), Ala-Archa (∆ 37.4º), Kurchatov (∆ 38.2º), Talaya (∆ 52.9º).
|
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 |
00-00-31.0 |
42.76 |
22.99 |
10 |
66 |
5.7/20 | 5.8/19 | 8 | 121 | IPC GS RAS (Accurate) | | 2 |
00-00-30.9 |
42.75 |
22.97 |
10 |
57 |
5.7/19 | 5.8/14 | 8 | 130 | IPC GS RAS (Preliminary) | | 3 |
00-00-33.1 |
42.66 |
23.01 |
10 |
185 |
| 5.7 | | 27 | CSEM | | 4 |
00-00-33.1 |
42.69 |
23.01 |
9.4 |
538 |
5.2/127 | 5.7/421 | | 25 | 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 presents with red star epicenter of this earthquake which origin was located on the territory of Bulgaria at the depth of 10 km, 28 km W of Sophia, the Capital of Bulgaria, 75 km S-S-W of Montana and 148 km W-S-W of Lovec. |
Figure 3 |
|
| Aftershock |
| GS RAS registered 2 aftershocks with М>4.2 within 5 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 |
| 20122085 | 2012-05-22 01:30:48.0 | 42.73 | 22.87 | 10 | 34 | - | 5.0/ 12 | 5-5.5 | Bulgaria | | 20122086 | 2012-05-22 02:13:26.0 | 42.58 | 23.04 | 10 | 12 | - | 4.3/ 6 | 3.5-4 | Bulgaria | |
| Macroseismic manifestations |
| In accordance with RIA NOVOSTI the walls collapsed in some buildings at the west of the country.
There are no reports about killed or injured persons.
Fig. 4 taken from the site of USGS NEIC presents the USGS Community Internet Intensity Map by 522 responses in 96 cities.
|
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism of the earthquake on May 22, 2012 at 00h 00m was computed in the IPC GS RAS with signs of P-wave first arrival at 106 stations, of which 10 stations recorded compression waves (“plus” signs) and 96 stations reported on extension waves (“minus” signs). The stations are located within 6º–96º interval of epicentral distances, mainly in the 1st and 4th quadrants of azimuth. Focal mechanism in stereographic projection on lower hemisphere is shown in Figure 5, its elements are presented in Table 2. Table 2 and Figure 6 also show the focal mechanism solution computed using WPhase Moment Solution method at the National Earthquake Information Center of the U.S. Geological Survey, USGS NEIC. The solutions of both centers are identical. The earthquake occurred at the prevalence of tension stresses oriented to the southwest. The steeply dipping NP1 nodal plane (DP=58º) has SE strike and the low-angle NP2 plane (DP=32-33º) has NW strike. Type of movement in the source along the both planes is normal fault.
Seismic moment of the earthquake on May 22, 2012 determined in the IPC GS RAS from P-wave spectrum at “Arti” station (Δ 26.48 º) is Mo=9.5*10**17 N*m. Average value of moment magnitude Mw calculated by the Kanamori formula Mw=6.0. According to the USGS NEIC, Mo=3.1*10**17 N*m, Mw=5.6.
|
| 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 |
| 13 | 233 | 74 | 16 |
9 | 141 | 135 | 58 | -101 | 336 |
33 | -73 | IPC GS RAS | | 13 | 214 | 76 | 43 |
1 | 305 | 126 | 58 | -87 | 302 |
32 | -93 | NEIC | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| NEIC - National Earthquakes Information Center of US Geological Service |
Figure 5 | 
Figure 6 |
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