2017 Valparaíso earthquake


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. 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.
Before this seismic event there was an unusual increase in seismic activity 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.
LocalityRegionUSGSONEMIPopulation
AndacolloCoquimboIV11k
CanelaCoquimboV9k
CombarbaláCoquimboV13k
Coquimbo CityCoquimbo RegionV228k
IllapelCoquimboV31k
La Serena CityCoquimboV221k
Los VilosCoquimboV21k
Monte PatriaCoquimboV31k
OvalleCoquimboV111k
PaiguanoCoquimboIII4k
PunitaquiCoquimboV11k
Río HurtadoCoquimboIV4k
AlgarroboValparaísoVII14k
PuchuncavíValparaísoVII19k
Quillota CityValparaísoVIVI91k
Greater ValparaísoValparaísoVIVII951k
La LiguaValparaísoVI35k
El TaboValparaísoVI13k
ColinaMetropolitan RegionVI146k
MelipillaMetropolitan RegionVI124k
Puente AltoMetropolitan RegionVI568k
San BernardoMetropolitan RegionV301k
City of SantiagoMetropolitan RegionVVI6.310k
TalaganteMetropolitan RegionVI74k
LituecheO'HigginsIV6k
NavidadO'HigginsVII7k
ParedonesO'HigginsIV6k
PichilemuO'HigginsIV16k
RancaguaO'HigginsIVVI242k
San FernandoO'HigginsIVVI74k
Santa CruzO'HigginsIV38k
CauquenesMauleV40k
ConstituciónMauleIV46k
CuricóMauleIV149k
LinaresMauleIII94k
Sagrada FamiliaMauleIV19k
CabreroBio-BioIII29k
Greater ConcepciónBio-BioIIIIV985k

Intensities of the earthquake on the scale of Mercalli in Argentina according to INPRES.
LocalityProvinceUSGSINPRESPopulation
City of San JuanSan Juan ProvinceIVIV447k
City of MendozaMendoza ProvinceIIIIV1.055k

Earthquakes Foreshock

The first foreshock quake was recorded at 19:46 and 22:49 on April 22, and had a magnitude of 4.8 Mw, with epicenter 32 km west of Valparaíso and 28.1 km deep.
DateTime localLocationCoordinatesDepthMagnitudeMMIAgency.
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.
DateTime localLocationCoordinatesDepthMagnitudeMMIAgency.
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.
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. 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 of the earthquake

This list includes information about the earthquake, which were measured by different seismological institutions worldwide.
DateTime localTime UTCRegionCoordinatesDepthMagnitudeAgency.
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, dependent on the Hydrographic and Oceanographic Service of the Chilean Navy, 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 the maximum heights were; 16 cm in the city of Valparaíso and 10 cm in the commune of Quintero.