Information message about the earthquake happened on May 28, 2004 in the North of Iran |
| The destructive earthquake with magnitude М=6.3 has happened on May 28, 2004 in the North of Iran at 16:38 Moscow time (12:38pm GMT). |
| 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 35 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 22 stations, accurate processing - with data 27 stations. |
| Figure 1 contains fragments of records from the following digital stations: kislovodsk (10,1 degrees), Arti (20.5 degrees), Borovoe (21,2 degrees), Obninsk (21,3 degrees), Pulkovo (27,1 degrees), Lovozero (32,9 degrees) – distance from epicenter to the station is specified in brackets.
Figure 2 contains fragments of records from the following digital stations: Ulan-Bator (41,9 degrees), Yakutsk (53,2 degrees), Magadan (63,7 degrees), bilibino (65,1 degrees), South-Sakhalinsk (65,2 degrees), College Outpost (77,9 degrees) - distance from epicenter to the station is specified in brackets. |
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 |
12-38-44.60 |
36.46 |
51.57 |
25 |
27 |
6.30/14 | 6.00/6 | 7.5 | | IPC GS RAS (предварительный) | | 2 |
.0 |
|
|
|
|
| | | | IPC GS RAS | | 3 |
.0 |
|
|
|
|
| | | | IPC GS RAS | | 4 |
.0 |
|
|
|
|
| | | | IPC GS RAS | | 5 |
.0 |
|
|
|
|
| | | | IPC GS RAS | | 6 |
.0 |
|
|
|
|
| | | | IPC GS RAS | | 7 |
.0 |
|
|
|
|
| | | | IPC GS RAS | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| Epicenter |
| Epicenter of the earthquake May 28, 2004 was located 70 km to the North from Iranian capital Teheran, between settlements Balada and Pil, in the Northern ridges of Mountain Elboroz. The earthquake’s zone in accordance with data of IIEES belongs to the Northern Elboroz deep rupture (fig. 3). |
Figure 3 |
|
| Aftershock |
| This earthquake has been accompanied with numerous aftershocks. In accordance with IIEES data 82 aftershocks with magnitudes from 1.7 to 4.8 have been registered in this area for the period between May 28 and May 30. |
| Macroseismic manifestations |
| This earthquake has been felt on the vast territory of Iran: from Southern coast of Caspian Sea to the Iranian center – Isfahan . 55 people have been killed, nearly 400 have obtained different injuries, hundreds of villages and towns in the North of Iran have destructions, electricity supply has been interrupted in Mazendaran province. Most destructions are observed in the Western part of Mazendaran province in the region of Sari town, and in the Eastern part of Gilian province in the region of Chalus.
This earthquake also has been felt in Azerbaijan (Astara and Lenkoran with intensity 3-4 MSK, Baku – 2-3 MSK), in Dagestan (Mahachkala – 2 MSK).
|
| Historical records |
| Broad information about the earthquake on May 28, 2004 is presented on WEB site of NEIC, USA . Data of this agency (obtained since 1900) display rather weak seismic activity in investigated area (fig.4). |
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Solutions of focal mechanism for this event have been obtained by IPC GS RAS from the first signs of P-wave arrivals at 80 stations. 60 stations registered the waves of compression - symbol "+", 20 stations – waves of expansion (symbol "-"). Table 2 presents elements of focal mechanism in accordance with data from IPC GS RAS, NEIC and HARVARD. Figures 5-7 present graphical view of stereographic projection with lower hemisphere of focal mechanism.
Solutions obtained in different centers with different methods are close. This earthquake has happened under the action of compression strengths oriented to the North-Eastern direction. Both nodal planes have North-Western-South-Eastern spread direction, the type of motion along steep falling planes – thrust, along more flat planes - over thrust (with presence in both cases of minor strike slip components).
Averaged value of seismic moment Мо has been determined by IPC GS RAS from Р-wave spectra at seismic stations "Obninsk" (delta 21,3 degrees) and "Arti (delta 20,5 degrees) and made 3.2* 10** 18 n*m. The value of moment magnitude from these data is equal to Mw = 6.3. The value of seismic moment Мо from NEIC data made 2.5* 10** 18 n*m, the value of moment magnitude - Mw = 6.2. The value of seismic moment Мо from Harvard data made 3.3* 10** 18 n*m, the value of moment magnitude - Mw = 6.3.
|
| 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 |
| | | |
| | | | | |
| | IPC GS RAS | | | | |
| | | | | |
| | IPC GS RAS | | | | |
| | | | | |
| | IPC GS RAS | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
Figure 5 |
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