Information message about the strong earthquake in China July 21, 2013 |
| The strong earthquake with a magnitude of M = 6.1, resulting in loss of life and destructions occurred on July 21, 2013 at 23:45 UTC (July 22 at 03:45 Moscow time) in Gansu Province in northwest China. |
| 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 18 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 32 stations, accurate processing - with data 54 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Taijon (∆ 18.9º), Mys Shultsa (∆ 22.5º), Vladivostok (∆ 23.1º), Kurchatov (∆ 24.6º), Ala-Archa (∆ 24.5º), Fig. 2 presents fragments of records obtained from digital stations Kuldur (∆ 25.0º), Erimo (∆ 31.3º), Yuzhno-Sakhalinsk (∆ 31.4º), Yakutsk (∆ 31.9º), Arti (∆ 37.8º). |
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 |
23-45-54.9 |
34.53 |
104.21 |
10 |
54 |
6.1/26 | 6.3/28 | 8.5-9 | 55 | IPC GS RAS (Accurate) | | 2 |
23-45-55.7 |
34.56 |
104.3 |
10 |
32 |
| 6.4/26 | 8.5-9 | 55 | IPC GS RAS (Preliminary) | | 3 |
23-45-57.1 |
34.553 |
104.249 |
10 |
581 |
6.0 Mw | | | 23 | CSEM | | 4 |
23-45-55.7 |
34.499 |
104.243 |
9.8 |
109 |
5.9 Mw | | | 22 | 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 |
| Red star in Figure 3 shows the epicenter of this earthquake, the origin of which was located in the Gansu Province of China at a depth of 10 km, 185 km SSE of Lanzhou, 430 km N of Chengdu and 431 km W of Xian. |
Figure 3 |
|
| Aftershock |
| GS RAS registered 2 aftershocks with М≥4.7 within 1.5 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 |
| 20132663 | 2013-07-22 00:09:42.0 | 34.74 | 104.52 | 10 | 15 | - | 4.7/ 11 | 4.5-5 | Gansu, China | | 20132662 | 2013-07-22 01:12:34.0 | 34.64 | 104.1 | 10 | 43 | - | 5.7/ 27 | 7-7.5 | Gansu, China | |
| Macroseismic manifestations |
| According to ITAR-TASS this earthquake in the northwest Gansu Province of China killed 94 people and injured 887. This was reported today by China Central Television. Most of the victims lived in the city of Dingxi and Minsyan and Chzhansyan counties. Now rescuers continue to work, trying to find survivors under the debris. On Monday, the National Meteorological Center said that the tremors were recorded at 07:45 local time. The main shock was accompanied with several hundred aftershocks.
The earthquake destroyed more than 1,200 homes, more than 20,000 people were injured. Fig. 4 presents USGS Community Internet Intensity Map obtained from site of USGS NEIC, based on 10 responses in 4 cities.
|
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of this earthquake was calculated at the IPC GS RAS by the signs of the first arrivals of P waves at 190 stations, including 177 stations which registered compression wave (the plus sign) and 13 stations which registered expansion wave (minus signs). These stations are located evenly in the range of epicentral distances of 4-99º along the azimuth. Focal mechanism in stereographic projection on the lower hemisphere is shown in Fig. 5, elements of the mechanism are shown in Table 2. Fig. 6, 7 present focal mechanism solutions obtained in USGS NEIC by USGS Body-Wave Moment Tensor Solution technique and in Quick CMT Catalog, USA by CMT technique. All solutions are close.
This earthquake has occurred under the action of NE oriented compression stresses and expansion steress oriented to the south. Both nodal planes decline steeply (DP=42-73º), NP1 plane is N-E oriented, NP2 is oriented to the south.
Type of motion along both planes – slips with uplift components, left side slip for NP1, right side slip for NP2.
Seismic moment was obtained in IPC GS RAS with spectra of Р waves registered at «Arti» (∆37.83º) and «Obninsk» (∆50.10º) stations makes Мо=2.0*10**18 N*m. Averaged value of moment magnitude makes Mw=6.2. In accordance with USGS NEIC Мо=8.5*10**17 N*m, Mw=5.9. In accordance with Quick CMT Мо=1.26*10**18 N*m, Mw=6.0. |
| 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 |
| 38 | 152 | 11 | 43 |
29 | 307 | 290 | 62 | 56 | 165 |
42 | 137 | IPC GS RAS | | 40 | 167 | 14 | 65 |
46 | 320 | 302 | 73 | 41 | 198 |
51 | 158 | NEIC | | 45 | 168 | 11 | 66 |
43 | 325 | 304 | 69 | 43 | 196 |
50 | 153 | 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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