Late Quaternary Paleoseismological Record of Large Earthquakes in the Lesser Antilles: Implications for Arc Segmentation and Long-Term Seismic Cycle of the Megathrust.
Description:
The seismic potential of the Lesser Antilles subduction zone is poorly known and highly debated. Only two strong damaging and deadly earthquakes have been reported in the historical period in on January 11th 1839 and on February 9th 1843 offshore Martinique and Guadeloupe islands, respectively but their source and magnitude are still uncertain. GNSS and coral data contradict each-others and we cannot conclude on the coupling rate of the plate interface. Given the threat posed by the possible occurrence of a large megathrust earthquake in the future in this region, it was urgent to gain information on the sources, magnitude and recurrence time of past pre-historical events. We present here the results of a submarine paleoseismological study that cover an exceptional ~100 kyr-long time period. We studied the sediments sampled in six up to 26 m-long giant piston cores collected on board of the French R/V Pourquoi-Pas? In deep fore-arc basins in the epicentral region of the 1843 earthquake. Using a multiproxy approach combining geophysical, geochemical, sedimentological analysis, foraminifera species biostratigraphy and radiocarbon dating, we identified, characterized and dated numerous turbidites and homogenites. Some occurred in all basins we sampled over a minimum distance of 160 km. We showed that they were likely triggered by at least 33 earthquakes in the last 120 ka. Peak ground accelerations calculated for various faults indicate that the sources are megathrust events. The spatial extent of the deposits suggests a seismic segmentation of the plate interface. Four of the seismic events, we called major margin events, led to up to 8 m-thick exceptional deposits of turbidites+homogenites. Over the last 60 ka, we inferred at least four 15 and 25 ka-long super seismic cycles in which the recurrence times of earthquakes shorten from ~5 to ~2 ka, what is an unusual behavior.
Session: Active Faults in the Caribbean and Central America
Type: Oral
Date: 4/20/2023
Presentation Time: 02:00 PM (local time)
Presenting Author: Chloé Seibert
Student Presenter: No
Invited Presentation:
Authors
Chloé Seibert Presenting Author Corresponding Author cseibert@ldeo.columbia.edu Institut de Physique du Globe de Paris |
Nathalie Feuillet feuillet@ipgp.fr Institut de Physique Du Globe de Paris |
Gueorgui Ratzov ratzov@geoazur.unice.fr Nice University |
Christian Beck beck.christian7@gmail.com Chaméry University |
Pierre Morena pierre.f.morena@gmail.com IFREMER, Université de Nice |
Lola Johannes ljohannes@mnhn.fr Muséum National d'Histoire Naturelle |
emmanuelle Ducassou emmanuelle.ducassou@u-bordeaux.fr Bordeaux Univrsity |
Antonio Cattaneo antonio.cattaneo@ifremer.fr IFREMER |
Chris Goldfinger chris.goldfinger@oregonstate.edu Oregon state University |
Eva Moreno eva.moreno@mnhn.fr Museum National d'Histoire Naturelle, Paris, , France |
Guillaume Saint-onge and THE CASEIS Group Guillaume_St-Onge@uqar.ca Université du Québec à Rimouski, Rimouski, Quebec, Canada |
Late Quaternary Paleoseismological Record of Large Earthquakes in the Lesser Antilles: Implications for Arc Segmentation and Long-Term Seismic Cycle of the Megathrust.
Category
Active Faults in the Caribbean and Central America