Information message about the strong earthquake in Mexico on December 11, 2011 |
| The strong earthquake with М=6.4 has occurred in Mexico on December 11, 2011 at 01:47 GMT (05:47 Moscow time) , it caused victims and destructions. |
| 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 17 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 30 stations, accurate processing - with data 35 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Hockley (∆ 12.4º), Juntas de Abangares (∆ 16.4º), Albuquerque (∆ 17.8º), College (∆ 56.6º). Fig. 2 presents fragments of records obtained from digital stations Kingsbay (∆ 76.5º), Petropavlovsk (∆82.5º), Kongsberg (∆ 84º), Tiksi (∆ 84.6º).
|
Figure 1
| 
Figure 2
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|
| 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 |
01-47-25.6 |
18.05 |
-99.85 |
70 |
35 |
6.4/11 | 6.6/9 | 6-6.5 | 82 | IPC GS RAS (Accurate) | | 2 |
01-47-23.9 |
18.04 |
-99.73 |
33 |
30 |
| 6.9/7 | 8-8.5 | 82 | IPC GS RAS (Preliminary) | | 3 |
01-47-26.4 |
18.07 |
-99.78 |
61.3 |
677 |
Mw 6.7 | | | 44 | CSEM | | 4 |
01-47-26.5 |
18.04 |
-99.8 |
64.9 |
488 |
Mw 6.5 | 6.2/396 | | 43 | 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 in Mexican State of Herrero at the depth of 70 km, in 38 km S-W of Iguala, in 118 km N of Acapulco and in 171 km S-S-W of Mexico City. |
Figure 3 |
|
| Macroseismic manifestations |
| In accordance with RIA-Novosti 3 persons became the victims of this earthquake. Iguala town is located close to the epicenter and suffered most of all.
Correspondent of RIA-Novosti confirmed that this earthquake was also felt in Mexico City and caused a little panic. Thousands of people simultaneously run away from buildings to the streets and tried to get away from the walls of the buildings as far as possible. All this was going in the deep darkness, as the electricity was switched off in many districts of the city.
Fig. 4, obtained from USGS NEIC , presents the map of intensities composed with messages from 897 respondents living in 124 places. |
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Fault-plane solution for the earthquake on December, 11, 2011 at 01h47m (GMT) was calculated in the IPC GS RAS by signs of P-wave first arrivals at 348 stations, of which 35 stations have registered compression waves (plus sign) and 313 stations - extension waves (minus sign). The stations are located within 1° - 98° range of epicentral distances and non-uniformly by azimuth - mostly in 1st, 2nd and 4th quadrants. Focal mechanism in the stereographic projection on lower hemisphere is shown in Figure 5, its elements are presented in Table 2. Also focal mechanism solutions calculated by the Centroid Moment Tensor technique at the National Earthquake Information Center of U.S. Geological Survey, USGS, and by the Moment Tensor technique in the Global CMT Catalog, United States, are given in Table 2 and Fig.6,7. The solutions are similar. The earthquake occurred at prevailing extension stress oriented to the south. Both nodal planes are striking in sub-latitudinal direction, dipping to the north at DP=35° for NP1 plane or to the south at DP=55° for NP2 plane. Type of movement is a normal fault for both planes.
According to the USGS, seismic moment Мо=6.3*10**18 N*m and moment magnitude Mw=6.5. According to the Global CMT Catalog, Мо=5.66*10**18 N*m and Mw=6.4. |
| 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 | 184 | 70 | 312 |
15 | 90 | 293 | 35 | -63 | 81 |
59 | -108 | IPC GS RAS | | 4 | 193 | 79 | 349 |
4 | 102 | 288 | 35 | -83 | 99 |
55 | -95 | NEIC | | 10 | 191 | 79 | 347 |
4 | 100 | 286 | 35 | -82 | 97 |
55 | -95 | Quick CMT | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
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