Interseismic Plate coupling and strain partitioning in the Northeastern Caribbean

Abstract

S U M M A R YThe northeastern Caribbean provides a natural laboratory to investigate strain partitioning, its causes and its consequences on the stress regime and tectonic evolution of a subduction plate boundary. Here, we use GPS and earthquake slip vector data to produce a present-day kinematic model that accounts for secular block rotation and elastic strain accumulation, with variable interplate coupling, on active faults. We confirm that the oblique convergence between Caribbean and North America in Hispaniola is partitioned between plate boundary parallel motion on the Septentrional and Enriquillo faults in the overriding plate and plateboundary normal motion at the plate interface on the Northern Hispaniola Fault. To the east, the Caribbean/North America plate motion is accommodated by oblique slip on the faults bounding the Puerto Rico block to the north (Puerto Rico subduction) and to the south (Muertos thrust), with no evidence for partitioning. The spatial correlation between interplate coupling, strain partitioning and the subduction of buoyant oceanic asperities suggests that the latter enhance the transfer of interplate shear stresses to the overriding plate, facilitating strike-slip faulting in the overriding plate. The model slip rate deficit, together with the dates of large historical earthquakes, indicates the potential for a large (M w 7.5 or greater) earthquake on the Septentrional fault in the Dominican Republic. Similarly, the Enriquillo fault in Haiti is currently capable of a M w 7.2 earthquake if the entire elastic strain accumulated since the last major earthquake was released in a single event today. The model results show that the Puerto Rico/Lesser Antilles subduction thrust is only partially coupled, meaning that the plate interface is accumulating elastic strain at rates slower than the total plate motion. This does not preclude the existence of isolated locked patches accumulating elastic strain to be released in future earthquakes, but whose location and geometry are not resolvable with the present data distribution. Slip deficit on faults from this study are used in a companion paper to calculate interseismic stress loading and, together with stress changes due to historical earthquakes, derive the recent stress evolution in the NE Caribbean.

Morphotectonics of the central Muertos thrust belt and Muertos Trough (northeastern Caribbean)

“…Vertical exaggeration is~2.0 at the seafloor. Lin, 2004Lin, , 2005 with only a small component of subduction of the North American plate beneath the Caribbean plate Mann et al, 2002;Manaker et al, 2008). In this setting, the Muertos convergent margin is an east-west trending tectonic feature located in the retroarc region of an inactive Cretaceous to Early Tertiary island arc and is a result of the convergence between the North American and the Caribbean plates (Ladd et al, 1981;Dillon et al, 1996).…”

“…Thick black arrows show the relative convergence direction between North American and Caribbean plates. Thin black arrows show the GPS-derived velocities with respect to North American plate (Manaker et al, 2008). The arrow length is proportional to the displacement rate.…”

Geology applied to the study of seismic microzoning of Santiago de los Caballeros, Dominican Republic

“…La convergencia de las placas caribeña y norteamericana es oblicua de unos 20 mm/año (DeMets et al, 2000), con un contexto general transpresivo, habiendo zonas de subducción al norte y sur de la isla, mientras que en su interior predominan los desgarres transpresivos (Mann et al, 1984;Manaker et al, 2008). En la actualidad dos de las zonas de falla transpresiva tienen una importante actividad tectónica, la Falla de Enriquillo que ha causado el reciente terremoto de Haití (12/01/2010) y la Zona de Falla Septentrional, cuya traza superficial pasa a escasos kilómetros de la ciudad de Santiago de los Caballeros.…”

“…El movimiento de la falla es transpresional senestro con un desplazamiento de unos 8 ±5 mm/año de acuerdo con Manaker et al (2008), resaltando la incertidumbre en la cuantificación del desplazamiento. El desplazamiento es coherente, al sumarlo con los 7 mm/año propuesto para la de Enriquillo, con el valor global de 20 mm/año determinado para la placa caribeña por De Mets et al (2000).…”

Long-term impacts of tropical storms and earthquakes on human population growth in Haiti and the Dominican Republic

“…(Manaker et al , 2008;Shedlock, 1999;Panagiotopoulos , 1995;Pubellier et al, 1991;Scherer , 1912) Figure 3 shows the spatial distribution of earthquakes with seismic moment magnitudes >4.5 whose exact locations or ruptured fault zones are relatively well known, including the Septentrional fault in the North and the Enriquillo fault in the South. As Table 2 outlines, the most severe seismic events have repeatedly damaged Haiti's two major cities, Port-au-Prince in Haiti's South and Cap-Haïtien in the North.…”