Information message about the strong earthquake on the coast of Ecuador, May 18, 2016 |
| The strong earthquake with М=6.6 has occurred on May 18, 2016 at 07:57 GMT (10:57 Moscow time) on the coast of Ecuador. Less than 9 hours after that there was another shock with M = 6.6 at 16:46 GMT (19:46 Moscow time). |
| Overall processing for the first earthquake was done with data from 32 stations, for the second earthquake - with data from 35 stations. |
| Fig. 1 presents fragments of records obtained by digital stations Juntas de Abangares (∆ 11.1º), Nana (∆ 12.7º), Albuquerque (∆ 42.4º), East Falkland Island (∆ 55.1º), College (∆ 80.4º) from the first shock. Fig. 2 presents fragments of records obtained by digital stations Juntas de Abangares (∆ 11.1º), Nana (∆ 12.7º), Albuquerque (∆ 42.4º), East Falkland Island (∆ 55.1º), College (∆ 80.4º) from the second shock. |
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 |
16-46-42.3 |
0.47 |
-79.7 |
33 |
35 |
6.6/18 | 6.5/13 | 7.5 | 78 | IPC GS RAS ([2]) | | 2 |
07-57-02.3 |
0.44 |
-79.78 |
33 |
32 |
6.5/16 | 6.3/16 | 7-7.5 | 78 | IPC GS RAS ([1]) | | 3 |
16-46-40.6 |
0.43 |
-79.68 |
10 |
435 |
Mw 6.8 | | | 57 | CSEM ([2]) | | 4 |
07-57-04.9 |
0.45 |
-79.84 |
40 |
287 |
Mw 6.7 | | | 46 | CSEM ([1]) | | 5 |
16-46-44.1 |
0.47 |
-79.64 |
31 |
103 |
Mw 6.8 | | | 60 | NEIC ([2]) | |
| 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 yellow star the epicenter of the first shock, its origin was located on the N-W coast of Ecuador, at a depth of 33 km, 58 km S-S-W of Esmeraldas, 158 km N-W of Quito, the Capital of Ecuador, and 181 km N-E of Portoviejo. ig. 3 presents with red star the epicenter of the second shock, its origin was located on the N-W coast of Ecuador, at a depth of 33 km, 9 km E-N-E of the first shock.
|
Figure 3 |
|
| Aftershock |
| These two earthquakes М=6.5 and М=6.6 was the strongest aftershock of the devastating earthquake on April 16 М=7.5 , to which 11 mines were registered foreshock М=4.9 and then for 15 aftershocks with magnitudes from M=4.8 to M=5.9 during month.
|
| Macroseismic manifestations |
| According to ITAR-TASS one person was killed by this earthquakes, 85 people were injured. Several settlements were left without electricity. Classes were canceled in schools.
According to USGS NEIC the earthquake was felt in Chile, Argentina, Brazil and Peru. Fig. 5 and Fig. 6 were obtained from USGS NEIC , it presents USGS Community Internet Intensity Map based on 104 responses in 22 cities (fig. 5), on 59 responses in 20 cities (fig. 6). |
Figure 4 | 
Figure 5 |
|
| Historical records |
| The epicenter of the devastating earthquake of April 16, 2016, M=7.5 was located 20 km S-W of the first shock and 30 km S-W of the second shock. Then according to ITAR TASS 655 persons were killed, 48 reported missing and more than 17,000 asked medical aid. Material damage to the country was estimated as several billion dollars. |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of the origin of earthquake at 07:57 GMT is presented in stereographic projection at lower hemisphere in fig. 6, 7. It was obtained by USGS NEIC with W-phase Moment Tensor (Mww) technique and by Quick CMT Catalog Center, USA with CMT technique. Elements of mechanism are presented in table 2.
Solutions on these data centers are almost identical.
The earthquake has caused under the prevalence of compression stresses oriented to the west(AZ=277º)and tensile stresses oriented to the east (AZ=86º) according to USGS NEIC; in case of Quick CMT Center – it was caused by compression stresses oriented to the west (AZ=272º) and tensile stresses oriented N-E (AZ=66º).
Nodal plane NP1 is almost vertical (DP=74º-76º) and strikes to the south(STK=172º-183º), NP2 – is dipping to the horizontal at an angle (DP=15º-20º) and strikes N-E (STK=23º-29º). The type of motion in the origin for NP1 – reverse fault with left latteral components, for NP2 – the thrust with right latteral components.
According to USGS NEIC – Mo=2.74*10**19 N*m, Mw=6.9; according to Quick СМТ Center – Mo=1.26*10**19 N*m, Mw=6.7. |
| 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 |
| 59 | 86 | 31 | 277 |
5 | 184 | 183 | 76 | 85 | 23 |
15 | 110 | NEIC | | 59 | 67 | 28 | 272 |
11 | 176 | 173 | 74 | 79 | 29 |
20 | 125 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 6 | 
Figure 7 |
|
