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WITHDRAWN A Pre-Colombian Tsunami in Lesser Antilles ? Identification of the Source Using Sediment Deposits and Tsunami Modeling

Description: 

WITHDRAWN No earthquake similar to the events of Sumatra in 2004 or in Japan in 2011 was firmly reported in the Lesser Antilles subduction zone. The two largest known tsunamis were generated by a strong intraplate earthquake in the Virgin Islands in 1867, and by the 1755 Lisbon earthquake. In this region, where the convergence rate between the American and Caribbean plates is low, the recurrence time of large earthquakes may be long (several centuries or millennia) and the historical record of such events is short. It is thus difficult to estimate their impact and it becomes crucial to gain information from longer-term geological records and tsunami modeling. An increasing number of old prehistoric tsunami deposits have been identified in recent years on several islands in the northern segment of the Lesser Antilles arc, between Antigua and Puerto-Rico, in Anegada, St-Thomas (Virgin Islands), Anguilla, and Scrub islands. We reviewed all those studies and evidenced that numerous tsunami deposits are about 500 years old (~1500 cal CE) likely suggesting a large event or a cluster of events during this Pre-Colombian period. We combined information provided by the sedimentological records (distribution and altitude of the sediment deposits) and tsunami models to discuss the origin of this middle age Pre-Colombian event(s). We listed all faults as possible sources of tsunamis in this complex tectonic region and used them to perform multiple run-up models by using high-resolution/topographic grids. By comparing the simulated wave heights and run-up distance to the sediment record, we showed that only magnitude 8-9 mega-thrust or outer-rise scenarios are able to generate tsunami waves that match the characteristic of the observed tsunami deposits. We will present here these results, discuss the realism of the models in light of the recent coupling models of the subduction zone based on short-term geodetic records, and also mention the hypothesis of these deposits being related to major Pre-Colombian hurricane(s).

Session: Active Faults in the Caribbean and Central America

Type: Oral

Date: 4/20/2023

Presentation Time: 11:00 AM (local time)

Presenting Author: Louise Cordrie

Student Presenter: No

Invited Presentation: 

Authors