The Valparaíso earthquake of April 2017 was a strong earthquake that shook the cities of Valparaíso and Santiago on Monday, April 24, 2017, at 18:38 local time (21:38 UTC). Its epicenter was located off the coast of the Valparaíso Region and had a magnitude of 6.9 Mw. On the scale of Mercalli, the earthquake reached an intensity of VII (Very Strong).
Before this seismic event there was an unusual increase in seismic activity (seismic swarm) that began on Saturday, April 22 and before the event of magnitude 6.9 more than 180 foreshocks had been recorded, the strongest being that of magnitude 6.0 that occurred in the dawn of the April 22, 2017.
Subsequent to this event, more than 1000 aftershocks have been recorded, including several earthquakes of magnitude greater than 5.0 and two earthquakes of magnitude 5.8 and 6.0 on Moment magnitude scale that occurred on Friday, April 28, 2017, at 12:30 and 13:05 local time respectively.
Modified Mercalli intensities for some localities The earthquake was widely felt throughout the central zone of Chile and in at least two provinces of Argentina.
Intensities of the earthquake on the scale of Mercalli in Chile according to ONEMI.
Locality Region USGS ONEMI Population Andacollo Coquimbo IV 11k Canela Coquimbo V 9k Combarbalá Coquimbo V 13k Coquimbo City Coquimbo Region V 228k Illapel Coquimbo V 31k La Serena City Coquimbo V 221k Los Vilos Coquimbo V 21k Monte Patria Coquimbo V 31k Ovalle Coquimbo V 111k Paiguano Coquimbo III 4k Punitaqui Coquimbo V 11k Río Hurtado Coquimbo IV 4k Algarrobo Valparaíso VII 14k Puchuncaví Valparaíso VII 19k Quillota City Valparaíso VI VI 91k Greater Valparaíso Valparaíso VI VII 951k La Ligua Valparaíso VI 35k El Tabo Valparaíso VI 13k Colina Metropolitan Region VI 146k Melipilla Metropolitan Region VI 124k Puente Alto Metropolitan Region VI 568k San Bernardo Metropolitan Region V 301k City of Santiago Metropolitan Region V VI 6.310k (+6M) Talagante Metropolitan Region VI 74k Litueche O'Higgins IV 6k Navidad O'Higgins VII 7k Paredones O'Higgins IV 6k Pichilemu O'Higgins IV 16k Rancagua O'Higgins IV VI 242k San Fernando O'Higgins IV VI 74k Santa Cruz O'Higgins IV 38k Cauquenes Maule V 40k Constitución Maule IV 46k Curicó Maule IV 149k Linares Maule III 94k Sagrada Familia Maule IV 19k Cabrero Bio-Bio III 29k Greater Concepción Bio-Bio III IV 985k
Intensities of the earthquake on the scale of Mercalli in Argentina according to INPRES.
Locality Province USGS INPRES Population City of San Juan San Juan Province IV IV 447k City of Mendoza Mendoza Province III IV 1.055k (+1M)
Foreshock The first foreshock quake was recorded at 19:46 (local time) and 22:49 (UTC) on April 22, and had a magnitude of 4.8 Mw, with epicenter 32 km west of Valparaíso and 28.1 km deep.
+ Precursor earthquakes magnitude greater than 5.0 Date Time local Location Coordinates Depth Magnitude MMI Agency.April 22, 201723:36:0730 km W of Valparaíso33.02S, 71.95W20 km6.0 MwVIEMSC.April 22, 201723:43:1830 km W of Valparaíso33.01S, 71.95W20 km5.0 MwIVEMSC.April 23, 201716:40:1045 km W of Valparaíso33.044S, 72.148W16 km5.6 MwIVNEIC.
Aftershock After the earthquake more than 1000 aftershocks were registered, the largest one had a magnitude of 6.0 Mw, with an epicenter 14 kilometers south of Valparaíso and 25.9 kilometers deep.
+ Aftershock of magnitude greater than 5.0 Date Time local Location Coordinates Depth Magnitude MMI Agency.April 24, 201718:45:58121 km NW of Valparaíso32.416S, 72.662W25,9 km5.5 Mw?GUC.April 24, 201718:46:0442 km W of Valparaíso32.972S, 72.072W16,4 km5.2 mbVINEIC.April 24, 201718:46:2435 km WNW of Valparaíso32.931S, 71.984W16,4 km5.4 mbVIINEIC.April 24, 201718:48:3139 km WSW of Valparaíso33.135S, 72.038W17,1 km5.0 mbVINEIC.April 24, 201722:43:0346 km W of Valparaíso33.161S, 72.093W23,9 km5.5 MwIVGUC.April 27, 201702:09:2239 km SW of Valparaiso33.265S, 71.956W22,5 km5.1 MwVINEIC.April 28, 201712:30:0637 km WSW of Valparaiso33.219S, 71.969W22 km5.9 MwVIINEIC.April 28, 201712:33:2847 km SW of Valparaiso33.30S, 72.02W20 km5.1 mbVEMSC.April 28, 201712:49:4147 km WSW of Valparaiso33.240S, 72.080W10 km5.1 MwVNEIC.April 28, 201712:58:3344 km SW of Valparaiso33.24S, 72.04W15 km5.4 MwIVEMSC.April 28, 201713:05:5714 km S of Valparaíso33.166S, 71.662W25,9 km6.0 MwVIGUC.April 28, 201714:41:4940 km SW of Valparaiso33.279S, 71.958W18 km5.3 MwVIINEIC.April 28, 201722:46:0236 km WSW of Valparaiso33.216S, 71.962W18,8 km5.1 MwVNEIC.May 13, 201713:54:4730 km W of Valparaiso32.95S, 71.93W30 km5.3 mbVIIEMSC.
Tectonic summary The April 24, 2017, M6.9 earthquake west of Valparaiso, Chile, occurred as the result of thrust faulting on or near the subduction zone interface between the Nazca and Pacific plates. At the latitude of this event, the Nazca plate is moving towards the east-northeast at a velocity of 74 mm/year with respect to South America, and begins its subduction beneath the continent at the Peru–Chile Trench, 80 km to the west of the April 24 earthquake. The size, location, depth and mechanism of this event are all consistent with its occurrence on the megathrust interface in this region.
While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Events of the size of the April 24, 2017, earthquake are typically about 40x20 km in size (length x width).
Chile has a long history of massive earthquakes, including the 2010 M 8.8 Maule earthquake in central Chile, which ruptured a ~400 km long section of the plate boundary immediately south of this 2017 event. The April 24, 2017, earthquake lies close to where the Juan Fernández Ridge enters the subduction zone, in a section of the plate boundary that ruptured in a M 8.0 earthquake in March 1985, and previously in the 1906 M 8.2 Valparaiso earthquake (reported by some to be as large as M 8.6). To the north of the Juan Fernandez Ridge, the subduction zone last ruptured in the M 8.3 Illapel earthquake in September 2015. This subduction zone also hosted the largest earthquake on record, the 1960 M 9.5 earthquake in southern Chile. Over the century prior to the April 24, 2017, earthquake, the region within 400 km of this event has hosted 19 M 7+ earthquakes. Prior to the April 24 M 6.9 event, the region immediately surrounding this earthquake hosted 9 other events of M 4.5 or larger over the preceding 2 days, including a M 5.9 earthquake on April 23, 2017. The 6.9 shock was also preceded by 4 seconds by a M~4 foreshock. Within an hour of the M 6.9 earthquake, 4 aftershocks of M 4.7-5.4 had been located.
Magnitude
This list includes information about the earthquake, which were measured by different seismological institutions worldwide. + Date Time local Time UTC Region Coordinates Depth Magnitude Agency.April 24, 201718:38:2821:38:28offshore Valparaiso, Chile33.089S, 72.116W24,1 km6.9 MwGUC.April 24, 201718:38:2721:38:27offshore Valparaiso, Chile33.03S, 71.85W10 km6.9 MwEMSC.April 24, 201718:38:3021:38:30offshore Valparaiso, Chile33.038S, 72.062W28 km6.9 MwNEIC.April 24, 201718:38:2121:38:21off the coast of Valparaiso, Chile33.072S, 72.298W14 km6.6INPRES.April 24, 201718:38:2921:38:29near the coast of Valparaiso, Chile33.02S, 71.86W20 km6.8 MwGFZ.April 24, 201718:38:2521:38:25offshore Valparaiso, Chile32.98S, 71.92W10 km6.7 MwINGV.April 24, 201718:38:2621:38:26near the coast of Valparaiso, Chile32.95S, 71.80W20 km6.9 MwUSP.April 24, 201718:38:2621:38:26offshore Valparaiso, Chile33.073S, 72.051W25 km6.9 MwAUST.April 24, 201718:38:2521:38:25off the coast of Valparaiso, Chile33.056S, 72.042W19 km6.9 MwIPGP.
Tsunami
The National Office of Emergency of the Interior Ministry declared a tsunami warning for the coasts of the Valparaíso and O'Higgins regions. A few minutes later, the National Tsunami Service of Chile (SNAM, by its initials in Spanish), dependent on the Hydrographic and Oceanographic Service of the Chilean Navy (SHOA, by its initials in Spanish), ruled out the probability of a tsunami off the coast of Chile. However, if the tsunami was generated, according to the Pacific Tsunami Warning Center (PTWC) the maximum heights were; 16 cm in the city of Valparaíso and 10 cm in the commune of Quintero.
See also List of earthquakes in 2017 List of earthquakes in Chile
References