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Earthquake Ruptures on Complex Fault Systems: Insights From Recent and Historical Earthquakes in Haiti

Description: 

Haiti has experienced several damaging M 7+ earthquakes in recent and historical times. Recent studies used primary archival sources to characterize the shaking distributions of the 1860 Jour de Pâques sequence and 1770 earthquake, and explored rupture scenarios using modern ground motion models. For the 1860 sequence, French-language newspapers published in Haiti provide more detailed macroseismic data than considered in previous studies, permitting identification and analysis of three damaging events. For the 1770 sequence, contemporaneous French-language reports provide detailed descriptions of the earthquake and its effects. Our results support the interpretation that the 1770 earthquake was the largest documented earthquake on the Enriquillo Plantain Garden Fault zone in the last 300 years, with estimated M 7.6. The preferred rupture scenario extends from east of Port-au-Prince to the west along the peninsula, terminating to the west near the Miragoâne pull-apart basin. This basin is interpreted as a left-stepping releasing bend along the EPGF zone, ~75 km west-southwest of Port-au-Prince. Part of the 1770 rupture may have been associated with overthrusting of the Massif de la Selle. Martin and Hough (2022) conclude that the 1860 sequence released appreciable strain near the Miragoane pull-apart, in the gap between the 2010 and 2021 earthquakes, providing an explanation for why these two rupture zones were not contiguous. The results further suggest that the 2010 and 2021 earthquakes together released less total moment than the 1770 earthquake. The 2010 earthquake may have occurred on the same fault(s) that ruptured in the 1770 earthquake or on one or more nearby subparallel faults. Results thus support the paradigm that fault zone complexity controls rupture segmentation, but rupture history on a complex fault is controlled by a combination of fault zone structure, dynamic processes, and prior rupture history that control individual earthquake ruptures.

Session: Active Faults in the Caribbean and Central America

Type: Oral

Date: 4/20/2023

Presentation Time: 08:30 AM (local time)

Presenting Author: Susan E. Hough

Student Presenter: No

Invited Presentation: 

Authors