Reanalysis of the 1761 transatlantic tsunami

Abstract

Abstract. The segment of the Africa–Eurasia plate boundary between the Gloria Fault and the Strait of Gibraltar has been the setting of significant tsunamigenic earthquakes. However, their precise location and rupture mechanism remain poorly understood. The investigation of each event contributes to a better understanding of the structure of this diffuse plate boundary and ultimately leads to a better evaluation of the seismic and tsunami hazard. The 31 March 1761 event is one of the few known transatlantic tsunamis. Macroseismic data and tsunami travel times were used in previous studies to assess its source area. However, no one discussed the geological source of this event. In this study, we present a reappraisal of tsunami data to show that the observations data set is compatible with a geological source close to Coral Patch and Ampere seamounts. We constrain the rupture mechanism with plate kinematics and the tectonic setting of the area. This study favours the hypothesis that the 1761 event occurred in the southwest of the likely location of the 1 November 1755 earthquake in a slow deforming compressive regime driven by the dextral transpressive collision between Africa and Eurasia.

A Review on Historical Tsunamis in the Canary Islands: Implications for Tsunami Risk Reduction

“…In the same document, this event is related to a strong earthquake that affected the Iberian Peninsula without serious damage, although in Lisbon it was stronger and some buildings collapsed. The results of a recent model of the 1761 tsunami propose wave heights along the northern coast of Tenerife smaller than 0.3 m and slightly higher to the northeast of the archipelago [44], in accordance with the reported lack of damages in the Canary Islands.…”

“…On 31 March 1761 another transoceanic tsunami was triggered by an 8.5 magnitude earthquake (Figure 1A, Table 1), with epicenter in the southwest of the Iberian Margin [43,44], that was felt in Portugal, Spain and Morocco [10,45]. The tsunami was reported along the south and west coasts of the Iberian Peninsula, the archipelagos of Azores and Madeira, the United Kingdom, and even in Barbados, being affected by waves higher than 1 m [10,25,33,43,45,46].…”

Exploring Offshore Sediment Evidence of the 1755 CE Tsunami (Faro, Portugal): Implications for the Study of Outer Shelf Tsunami Deposits

“…High age uncertainties were also reported in other offshore paleo-tsunami studies [3,96], stressing that age control of tsunami deposit is difficult and needs to be conducted carefully. Another issue of the age uncertainty is the distinguishing of the transatlantic tsunami in 1761 CE [97] from the 1755 CE event. The source area of the 1761 CE tsunami is proposed to be in the Southwest Iberian Margin similar to the 1755 CE tsunami [97].…”

“…Another issue of the age uncertainty is the distinguishing of the transatlantic tsunami in 1761 CE [97] from the 1755 CE event. The source area of the 1761 CE tsunami is proposed to be in the Southwest Iberian Margin similar to the 1755 CE tsunami [97]. Despite the effects of the earthquake in mainland Portugal, the related tsunami had about zero impact in respect to human and economic losses [47].…”

A new tsunami runup predictor

“…NSWING solves the NSW equations in a Cartesian or spherical reference system, allows for nested grids, and employs a moving boundary algorithm to track the shoreline motion during the inundation like Cornell multi-grid coupled tsunami model (COMCOT) (Liu et al 1995(Liu et al , 1998. The code was benchmarked according to the analytical tests presented by Synolakis et al (2008) and applied in Miranda et al (2014), , Wronna et al (2015), Baptista et al (2017) and Wronna et al (2017Wronna et al ( , 2019. We used a synthetic bathymetry with the dimensions of 80 × 520 km 2 with a constant slope (Fig.…”