July 8, 1730 Earthquake: Valparaiso, Chile

Ref #415:

The Valparaiso earthquake. A severe earthquake occurred between 01:00 and 02:00 [local time] in Santiago. The inhabitants dressed and hurried into the streets. Then followed three less severe tremors. But at 04:45 [local time] on July 8, 1730, the area was struck by a shock so severe that people found it difficult to remain standing. A large part of the city was completely destroyed and clouds of dust arose from the ruins. Since the people had time to flee into the streets, only two women perished. Between 12:00 and 13:00 [local time] there was another earthquake, almost equal in force to the previous one. Innumerable tremors continued during the next two days, and with diminished frequency over several months.

This was one of the most severe earthquakes in the history of Chile. Severe damage occurred approximately between 30o and 36o S., from La Serena to Chillan.

In La Serena, the parish church was destroyed. In Coquimbo, several houses and churches were slightly damaged. The destructive effects of the earthquake were more apparent in the area north of La Serena, but it is difficult to estimate the northern boundary of the effect of the earthquake because that section of the country was not settled at the time. In Chillan, the damage was less than in La Serena, although several buildings were destroyed and the earthquake greatly frightened the inhabitants. In Valparaiso, some houses were ruined, not only in the low areas, but also on the slopes - something that did not occur even during the earthquake of 1906. Only the house of the governor was saved, although it too was damaged, as well as the arsenal and one auxiliary building. Coquimbo and the mountain villages of Illapel, Petorca and Tiltil were seriously damaged. In the mines the machinery for crushing ore broke down. Strong shocks were also felt in Concepcion but they did not cause any destruction. In Rengo, the church was destroyed. The earthquake was strongly felt as well in three mountain provinces of Argentina, where it terrified the inhabitants of Cordoba. The source of the earthquake was probably located close to the mouth of the Aconcagua River.

A destructive tsunami, which enveloped the coast for a distance of over 1000 km, occurred almost simultaneously with the second earthquake.

Ref #11799:

The earthquake and tsunami that occurred in Metropolitan Chile on July 8th 1730 at 4:30 am local time, have been recognized as the largest to occur in this region since the beginning of written history [Montessus de Ballore, 1912]. The event was preceded by a strong foreshock, which although produced a tsunami that was observed in Concepción, its effects were not as large as those reported for the main shock [Urbina et al., 2016].

The shaking produced by the 1730 earthquake caused severe damage to buildings along >1000 km of the coast, from Copiapó (30°S) to Concepción (36.6°S) Severe damage to buildings was also reported on the other side of the Andes, in Mendoza, Argentina.

The historical observations at Valparaíso and Penco suggest that the magnitude for the 1730 earthquake was in the range of Mw 9.1-9.3. This estimate is in agreement with the tsunami heights observed in Japan in 1730, which indicate an overall tsunami size consistent with instrumentally recorded Chilean earthquakes of magnitudes of about Mw 9.3.

Origin times and magnitudes:

July 8 4:45 am [local time], mag. 8.75 (ref #252)

July 8 4:45 am [local time] (ref #415)

July 8 09:00 UTC (ref #79)

July 8 08:45 UTC 32.5S, 71.5W, mag 8.25 (ref #150)

July 8 10:00 UTC, 33.050S, 71.63W, mag 8.7 (ref #1206)

July 8 13:00 UTC, 32.5S, 71.5W, mag. 8.7 (ref #552)

July 8 13:00 UTC, mag. 8.75 (ref #164)

Mw 9.1-9.3 (ref #11799)

Mw 9.0 (ref #11800)