Informational message about the strong earthquake in northern Mexico, April 4, 2010 |
| A strong earthquake with M = 7.2 occurred in northern Mexico on April 4, 2010 at 22:40 GMT (April 5, at 02:40 Moscow time), resulting in casualties. |
| 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 36 stations, accurate processing - with data 45 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Yakutsk (∆ 72.7º), Erimo (∆ 77º), Lovozero (∆ 77.7º), Hailar (∆ 85.4º), Kasperske Hory (∆ 87.1º). Fig. 2 presents fragments of records obtained from digital stations Obninsk (∆ 89.7º), Talaya (∆ 89.8º), Arti (∆ 91.6º), Kurchatov (∆ 96.6º), Kislovodsk (∆ 101.6º). |
Figure 1
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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 |
22-40-44.2 |
32.19 |
-115.14 |
10 |
45 |
7.2/18 | 6.4/19 | 10-10.5 | 49 | IPC GS RAS (Accurate) | | 2 |
22-40-44.9 |
32.25 |
-115.14 |
10 |
36 |
7.2/17 | 6.4/18 | 10-10.5 | 49 | IPC GS RAS (Preliminary) | | 3 |
22-40-47.7 |
32.378 |
-115.045 |
10 |
272 |
7.0Mw | | | 110 | CSEM | | 4 |
22-40-41.0 |
32.128 |
-115.303 |
10 |
315 |
7.2Mw | | | 79 | NEIC (Accurate) | | 5 |
22-40-45.7 |
32.192 |
-115.095 |
10 |
172 |
7.0Mw | 6.5/55 | | 111 | NEIC (Preliminary) | |
| 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 |
| Red star in fig.3 shows the epicenter of the earthquake, the focus of which was located in Mexico's border states of Baja California and California, at the depth of 10 km, 56 km south-east of Mexicali, Mexico, 193 kilometers east-southeast from San Diego, USA, and 320 kilometers west-southwest of Phoenix, USA. |
Figure 3 |
|
| Aftershock |
| GS RAS registered 5 aftershocks with М>5 within 13 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 |
| 20101276 | 2010-04-04 23:15:16.0 | 32.31 | -115.02 | 10 | 21 | - | 5.5/ 12 | 6.5-7 | Calif.-Baja Calif. border region | | 20101277 | 2010-04-04 23:25:08.0 | 32.06 | -114.91 | 10 | 18 | - | 5.4/ 15 | 6-6.5 | W. Arizona-Sonora border region | | 20101278 | 2010-04-05 00:07:09.0 | 32.14 | -114.84 | 10 | 17 | - | 5.2/ 12 | 5.5-6 | W. Arizona-Sonora border region | | 20101279 | 2010-04-05 01:25:38.0 | 32.56 | -114.91 | 10 | 11 | - | 4.9/ 10 | 5-5.5 | W. Arizona-Sonora border region | | 20101283 | 2010-04-05 11:14:18.0 | 32.61 | -115.39 | 10 | 16 | - | 5.1/ 6 | 5.5-6 | Calif.-Baja Calif. border region | |
| Macroseismic manifestations |
| In accordance with RIA-Novosti this earthquake killed two and injured 233 people and badly damaged government offices, hospitals, residential buildings and irrigation canals in the administrative center of the state of Baja California - the city of Mexicali.
In accordance with NEIC this earthquake was felt in Mexico, Baja California, and in the United States, California. Fig. 4, downloaded from the site USGS NEIC presents the map of intensity obtained over the telephone calls made by 73,048 respondents from 30 settlements. |
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solutions of the earthquake on April 4, 2010 at 22:40 GMT were obtained with CMT method by NEIC of USGS and Global CMT Catalog, USA. They are listed in Table 2 and shown in Fig. . 5, 6. These solutions are close. This earthquake has occurred under the action of almost equal expansion and compressive forces oriented east and south, respectively. Both nodal planes are rather steeply falling (angles of declination DP = 81 º -43 º), one plane has a northeast direction of propagation, the other - north-west. The type of motion along both planes is characterized by the drift with fault components - right-side drift for NP1and left-side drift for NP2.
The value of the seismic moment for the earthquake on April 4, 2010 was obtained by IPC GS RAS with spectrum of P-waves at “Obninsk” station (delta 89.7 degrees) and it makes Mo = 1.5 * 10 ** 19 n * m. The average value of moment magnitude calculated by Kanamori formula makes Mw = 6.8.
According to USGS the value of seismic moment Mo makes 9.6 * 10 ** 19 n*m and the value of moment magnitude Mw = 7.3. According to the Global CMT Catalog - Mo = 7.28 * 10 ** 19 Nm, Mw = 7.2.
|
| 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 |
| 23 | 81 | 39 | 193 |
41 | 329 | 321 | 80 | -131 | 220 |
43 | -13 | NEIC | | 1 | 87 | 9 | 177 |
81 | 351 | 312 | 84 | -173 | 221 |
83 | -6 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 5 | 
Figure 6 |
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