Oblique convergence causes both thrust and strike-slip ruptures during the 2021 M 7.2 Haiti earthquake

A devastating magnitude 7.2 earthquake struck Southern Haiti on 14 August 2021. The earthquake caused severe damages and over 2000 casualties. Resolving the earthquake rupture process can provide critical insights into hazard mitigation. Here we use integrated seismological analyses to obtain the rupture history of the 2021 earthquake. We find the earthquake first broke a blind thrust fault and then jumped to a disconnected strike-slip fault. Neither of the fault configurations aligns with the left-lateral tectonic boundary between the Caribbean and North American plates. The complex multi-fault rupture may result from the oblique plate convergence in the region that the initial thrust rupture is due to the boundary-normal compression and the following strike-slip faulting originates from the Gonâve microplate block movement, orienting towards the SW-NE direction. The complex rupture development of the earthquake suggests that the regional deformation is accommodated by a network of segmented faults with diverse faulting conditions.

Historical earthquakes in the Lower Segura basin (SE Spain): geological and archaeological evidence from pre-roman to modern times

This paper deals with the analysis of ancient and historical earthquakes in the Lower Segura Depression (SE Spain) at the northern end of the Eastern Betic Cordillera Shear Zone (EBSZ), which is defined within the area by the Lower Segura blind-thrust fault. The work summarizes and updates the existing information on the building and environmental damage dispersed throughout several historical documents, as well as the new historical and archaeological research on the area. The analyses performed consider the evolving paleogeography of the old estuarine zone defined by Ibero-Roman "Sinus ilicitanus" and the ancient prograding delta of the Segura River over the marshes. Topographic data from old descriptions of the zone together with the analysis of the geometry of the medieval irrigation system in the growing delta from pre-Roman to modern (18th century) times, allow the paleogeographic evolution of the zone, until the eventual artificial infilling of the old embayment, to be outlined. Several strong earth- quakes (Intensity ≥ VIII EMS-98) occurred in the area during different historical times. Building damage for the different events was variable depending on the number of settlements (and increasing population) within the ancient embayment. Maximum Intensity X during the most recent earthquake (AD 1829 Torrevieja) mainly occurred over old lands reclaimed in the 18 th century. In addition, dominant earthquake secondary effects (EEEs) were caused by liquefaction processes. This study analyzes the dimensions and distribution of these EEEs for the two main earthquakes in the zone during the years AD 1048 and AD 1829 using the ESI-07 intensity scale. The results draw important inferences on the role of ancient paleo-geography in seismic hazard data from past earthquakes.