On the footprints of a major Brazilian Amazon earthquake

Abstract

Combining historical accounts and seismological studies, three hundred years of dormant information emerged as a source of the largest known seismic event that rocked Brazil since the beginning of our colonization. The probable epicenter location of the 1690 tremor lies on the left bank of the Amazon River, about 45 km downstream from the modern day Manaus. A year later, while passing this area, a missionary met witnesses of the tremor and observed remarkable changes in the topography and vegetation along the margin of the river. By 1692 another priest confirmed this event and the occurrence of large waves in the river, which led to the flooding of the Native Indians' terrains. The tremor spread seismic waves throughout the forest and shook indigenous constructions as far as one thousand kilometers away. A calculation of the seismic parameters shows an estimated magnitude of 7, a maximum intensity of IX MM and a felt area of about 2 million km 2 . Due to the long recurrence period for this type of tremor, the discovery of one of these events is valuable for seismic global intraplate studies. As for Brazil, it unravels the myth that the country was never hit by severe earthquakes.

Probabilistic seismic hazard analysis for a nuclear power plant site in southeast Brazil

“…The largest known crustal earthquake (1955, Mato Grosso state) had a magnitude 6.2 mb, (but probably Mw , 6) and was felt up to 500 km away (Barros et al, 2009). There is also limited historical evidence for a magnitude ~7 in the Amazon in 1690 (Veloso, 2014).…”

Late Pleistocene–Holocene stress in the South American intraplate evidenced by tectonic instability in central Amazonia

“…Although in situ measurements of seismological events are still scarce in Brazilian Amazonia, the available data are compatible with the proposed present-day tectonic activity. The first seismological report was made by a missionary in 1692, who described severe environmental damage (see descriptions in IHGB, 1917) close to the mouth of the Negro River, later related to an earthquake of magnitude up to 7.0 (Veloso, 2014) on the Richter scale. In addition, earthquakes of magnitudes 5.1 and 5.5 that affected the left bank of the Negro river in 1963 and 1983 (Assumpção et al, 1983) were related to NW-striking maximum horizontal compressive stresses (Assumpção and Suárez, 1988).…”

Conditioning Factors of “Terras Caídas” in Lower Solimões River - Brazil

“…Manaus is considered a seismogenic zone with epicenters located around the confluence between the Negro and Solimões rivers (COSTA et al, 1996;MIOTO, 1993). Downstream of the study area, an earthquake with an estimated magnitude of ~7 was recorded in 1690, being considered the largest in the Amazon region, afterwards earthquakes were recorded in the region of the municipality of Codajás in 1963, upstream of the study area, with magnitude of 5.1, result of a reverse fault oriented NNE; and in the municipality of Manaus in 1980, with magnitude 3.4, the result of a reverse fault oriented approximately to NNW, probably the tremors of these events affected the study area (ASSUMPÇÃO; SUÁREZ, 1988;VELOSO, 2014). However, at Manacapuru station (MACA) in 2014-2020 historical series there are no seismic records, indicating that, in recent years, when the events of "Terras Caídas" have intensified, this has not been a conditioning factor for Xiborena Island.…”