Information message about the devastating earthquake on the coast of central Chile, September 16, 2015 |
| Devastating earthquake М=8.3 occurred on September 16, 2015 at 22:54 GMT (September 17 at 01:54 Moscow time) on the coast of central Chile, resulting in human casualties and destruction. |
| 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 24 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 34 stations, accurate processing - with data 50 stations. |
| Fig. 1 presents fragments of records obtained from digital stations East Falkland Island (∆ 22.4º), Juntas de Abangares (∆ 43.6º), Sanae (∆ 53.7º), Hockley (∆ 65.4º), Albuquerque (∆ 73.9º). Fig. 2 presents fragments of records obtained from digital stations Vasula (∆ 120.6º), Pulkovo (∆ 122.6º), Obninsk (∆ 125.4º), Kislovodsk (∆ 127.9º), Garni (∆ 128.9º). |
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 |
22-54-30.2 |
-31.6 |
-71.61 |
25 |
50 |
8.3/24 | 7.3/6 | 10.5 | 45 | IPC GS RAS (Accurate) | | 2 |
22-54-32.3 |
-31.71 |
-71.82 |
33 |
34 |
8.1/25 | 7.3/5 | 9.5-10 | 60 | IPC GS RAS (Preliminary) | | 3 |
22-54-33.0 |
-31.566 |
-71.582 |
30 |
322 |
Mw 8.3 | | | 19 | CSEM | | 4 |
22-54-33.2 |
-31.57 |
-71.654 |
25 |
285 |
Mw 8.3 | | | 19 | 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 the epicenter of this earthquake, its origin was located on the coast of Central Chile, at a depth of 25 km, 42 km W of Illapel, 156 km N of Valparaiso, 183 km S-S-W of Coquimbo and 225 km N-N-W of Santiago, the capital city of Chile. |
Figure 3 |
|
| Aftershock |
| Geophysical Survey registered 33 aftershocks M>=4.9 within the day after the main shock. Table 8 presents the strongest of them M>=5.8. |
| 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 |
| 20153262 | 2015-09-16 23:03:56.0 | -31.78 | -71.57 | 33 | 12 | - | 6.0/ 3 | 6 | Near coast of Central Chile | | 20153265 | 2015-09-16 23:16:07.0 | -31.69 | -71.72 | 33 | 13 | - | 6.3/ 2 | 6.5-7 | Near coast of Central Chile | | 20153259 | 2015-09-16 23:18:41.0 | -31.62 | -71.46 | 33 | 33 | - | 6.6/ 6 | 7-7.5 | Near coast of Central Chile | | 20153266 | 2015-09-16 23:38:04.0 | -31.92 | -72.13 | 33 | 18 | - | 6.0/ 5 | 6 | Off coast of Central Chile | | 20153260 | 2015-09-17 01:33:04.0 | -31.65 | -71.94 | 33 | 20 | - | 5.8/ 6 | 5.5 | Near coast of Central Chile | | 20153261 | 2015-09-17 01:41:07.0 | -31.23 | -71.59 | 33 | 25 | - | 5.8/ 7 | 5.5 | Near coast of Central Chile | | 20153268 | 2015-09-17 03:55:05.0 | -31.08 | -71.43 | 33 | 24 | - | 6.3/ 4 | 6.5-7 | Near coast of Central Chile | | 20153264 | 2015-09-17 04:10:29.0 | -31.59 | -71.62 | 33 | 28 | - | 6.3/ 6 | 6.5-7 | Near coast of Central Chile | |
| Macroseismic manifestations |
| According to ITAR-TASS this earthquake killed 12 people. More than 185,000 people were left without electricity in the region of Coquimbo. The ceiling collapsed in a supermarket in the city of La Serena.
According to eyewitnesses, tall buildings swayed in the Chilean capital. Fluctuations in the Earth's crust were felt in various cities in Chile, neighboring Argentina and southern Brazil. It was declared a threat of a tsunami. According to Pacific Tsunami Warning Centre the maximum tsunami wave height of 4.75 meters was recorded in Coquimbo, Chile. Maximum wave reached a height of 0.5 m in Peru and 20 cm. in Mexico.
Fig. 4 was obtained from USGS NEIC , it presents Community Internet Intensity Map based on 932 responses in 104 cities. |
Figure 4 |
|
| Historical records |
| This earthquake has occurred 505 km. N-N-E of the devastating earthquake of February 27, 2010 М=8.7. Then the earthquake and accompanying tsunami killed more than 700 people. |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of the origin was obtained in IPC GS RAS with signs of initial arrivals of longitudinal waves at 60 stations, 55 ot these stations registered compression waves (plus sign) and 5 stations registered tensile waves (minus sign). The stations are located in the interval of epicentral distances 1-97º and azimuth alignment Az=0-356º. Focal mechanism in stereographic projection at lower hemisphere is shown in fig. 5. The elements of the mechanism are shown in table 2. Fig. 6, 7 present focal mechanism solutions of the origin obtained by USGS NEIC with W-phase Moment Tensor (Mww)technique and in Quick CMT Catalog Center, USA with CMT technique. These solutions obtained according to data of different centers are close.
This earthquake has occurred under the action of prevailing compression stress oriented to the west and tensile stress oriented to the the east. Nodal plane NP1 in all solutions is nearly vertical , nodal plane NP2 is flat. In GS RAS and US GS solutions NP1 plane strikes S–N, in CMT solution it strikes N-S-E. The type of motion for steeply dipping plane NP1 - uplift (with a small component of the left-lateral slip in CMT case), the type of motion for NP2 plane – overthrust with slip components (in USGS case - left-lateral slip, in GS RAS and CMT case - right-lateral slip).
According to USGS NEIC – Mo=3.191*10**21 N*m, Mw=8.3; according to СМТ – Mo=2.86*10**21 N*m, Mw=8.2. |
| 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 |
| 61 | 108 | 25 | 254 |
14 | 351 | 176 | 71 | 105 | 316 |
24 | 53 | IPC GS RAS | | 64 | 93 | 26 | 268 |
2 | 359 | 180 | 71 | 92 | 353 |
19 | 83 | NEIC | | 66 | 68 | 24 | 264 |
6 | 171 | 169 | 69 | 84 | 5 |
22 | 106 | 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 |
|
