The 184th anniversary of the Concepción earthquake, M ~ 8.5

This earthquake affected Robinson Crusoe Island (J. Fernández)

This event is among the most widely documented Chilean earthquakes and served to know the causes that generate them thanks to the contribution of the English naturalist Charles Darwin.

Earthquake Parameters:
Data: 20 February, 1835
Time: 11:30am
Area-Epicentre: Concepción
Magnitude: 8,5 (in different sources)

Main events, damage and felt area:
One of the more widely documented Chilean historical earthquakes, described by Charles Darwin in his "The Voyage of the Beagle". Descriptions of the phenomenon in various locations indicate that there were at least two major shocks in a space of two minutes.

The first tremor was felt in Concepcion at 11:40 a.m., but it was not strong enough to cause panic. Darwin felt the main- shock on land near Valdivia, and his description matches that of a distant regional earthquake.

No damage in Valdivia, but total destruction in Concepción and on Quiriquina Island. A large foreshock was felt less than two minutes before the main shock.

The island of Quiriquina was uplifted 8 feet, Santa Maria Island 8 to 10 feet, Talcahuano 4 to 5 feet, Tubul 6 feet, according to Darwin.

Most of the uplift disappeared during the aftershock sequence. Subsidence was reported in the Maule estuary. Casual ties in Concepcion numbered 5 dead and 30 missing. Some people were killed in Talcahuano, Chillan, Constitución, Cauquenes, Talca, and elsewhere in the Central Valley south of Rancagua. Damage in Santiago. Felt from Chiloé to Copiapó and in Western Argentina (Lomnitz, 2004),

A historical map of Chile given by Lomnitz (2004)

A moment magnitude Mw=8.25 (+-0.20) is given by SARA earthquake catalogue (2016), which I am a co-author, that was developed by The South America Risk Assessment (SARA) project. The seismic event also generated a tsunami of proportions that added more destruction. Within the history of Chile, the earthquake of February 20, 1835 is known as "La Ruina".

Concepcion Modern City (https://www.visitchile.com/es/concepcion/)

The town of San Juan Bautista, Robinson Crusoe Island (https://en.wikipedia.org/wiki/Juan_Fern%C3%A1ndez_Islands)

Sources:
Lomnitz C. (2004). Major Earthquakes of Chile: A Historical Survey, 1535-1960. Seismological Research Letters, 75:3:May/June 204, 368-378.

SARA Project:
https://sara.openquake.org/hazard_rt4

The Voyage Of The Beagle by Charles Darwin:
chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http://www.boneandstone.com/articles_classics/voyage_of_beagle.pdf

Figs.
https://www.archivodesastre.cl/concepcion-1835

Robinson Crusoe Island (J. Fernández)
https://en.wikivoyage.org/wiki/Juan_Fern%C3%A1ndez_Islands
https://it.wikipedia.org/wiki/Isole_Juan_Fern%C3%A1ndez

More inf.
https://www.biobiochile.cl/noticias/2015/02/22/la-historia-del-terremoto-de-concepcion-que-sorprendio-a-charles-darwin-en-chile.shtml
http://www.memoriachilena.gob.cl/archivos2/pdfs/MC0012469.pdf
https://es.wikipedia.org/wiki/Anexo:Terremotos_en_Chile
chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http://www.geologie.ens.fr/~vigny/articles/Chili-Concepcion-Eq-1-UK.pdf
http://www2.udec.cl/gema/Ter_hist/20_2_1835.html