GPS estimates of microplate motions, northern Caribbean: evidence for a Hispaniola microplate and implications for earthquake hazard

Abstract

SUMMARY We use elastic block modelling of 126 GPS site velocities from Jamaica, Hispaniola, Puerto Rico and other islands in the northern Caribbean to test for the existence of a Hispaniola microplate and estimate angular velocities for the Gônave, Hispaniola, Puerto Rico‐Virgin Islands and two smaller microplates relative to each other and the Caribbean and North America plates. A model in which the Gônave microplate spans the whole plate boundary between the Cayman spreading centre and Mona Passage west of Puerto Rico is rejected at a high confidence level. The data instead require an independently moving Hispaniola microplate between the Mona Passage and a likely diffuse boundary within or offshore from western Hispaniola. Our updated angular velocities predict 6.8 ± 1.0 mm yr−1 of left‐lateral slip along the seismically hazardous Enriquillo‐Plantain Garden fault zone of southwest Hispaniola, 9.8 ± 2.0 mm yr−1 of slip along the Septentrional fault of northern Hispaniola and ∼14–15 mm yr−1 of left‐lateral slip along the Oriente fault south of Cuba. They also predict 5.7 ± 1 mm yr−1 of fault‐normal motion in the vicinity of the Enriquillo‐Plantain Garden fault zone, faster than previously estimated and possibly accommodated by folds and faults in the Enriquillo‐Plantain Garden fault zone borderlands. Our new and a previous estimate of Gônave‐Caribbean plate motion suggest that enough elastic strain accumulates to generate one to two Mw∼ 7 earthquakes per century along the Enriquillo‐Plantain Garden and nearby faults of southwest Hispaniola. That the 2010 M= 7.0 Haiti earthquake ended a 240‐yr‐long period of seismic quiescence in this region raises concerns that it could mark the onset of a new earthquake sequence that will relieve elastic strain that has accumulated since the late 18th century.

Crustal deformation and surface kinematics after the 2010 earthquakes in Latin America

“…This is in agreement with the discussions presented by several authors, e.g. Boschman et al (2014), Benford et al (2012), Calais et al (2016), DeMets et al (2007, Leroy and Mauffret (1996), Lundgren et al (1999), and Symithe et al (2015).…”

“…These findings are in agreement with the conclusions presented by Benford et al (2012), Symithe et al 2015, andCalais et al (2016). The Chorotega block is moving about 10 mm/a in the N60°E direction with respect to the Caribbean plate.…”

Crustal Structure and Fault Geometry of the 2010 Haiti Earthquake from Temporary Seismometer Deployments

“…The aftershock mechanisms (primarily thrust) trend differently from what was initially expected based on the predominant strike-slip tectonic style of southern Haiti. Upon re-evaluation, however, it is consistent with the transpressional deformation pattern clearly visible in the older thrust belt geology (Pubellier et al, 2000) and in the interseismic GPS measurements (Calais et al, 2010;Benford et al, 2012).…”

The northern Caribbean plate boundary in the Jamaica Passage: Structure and seismic stratigraphy

“…Their hypothesis is thus that the deformation (strike-slip and compressive) is entirely localized on the block boundaries, here the EPGFZ. Benford et al (2012b) nonetheless acknowledge that the fault-normal convergence predicted by their model is partitioned onto the EPGFZ and structures north and possibly south of the fault zone. We evidence some shortening in the Jamaica Passage, not only in the two half-graben Basins crosscut by the EPGFZ, but also in the Albatros Basin, south of the trace of the EPGFZ.…”

“…The EPGFZ is one of the major structure accommodating ~7 mm/yr of pure strike-slip motion (Manaker et al, 2008). However, recent block modeling based on GPS velocities (Calais et al, 2010;Benford et al, 2012b;Symithe et al, 2015) predict along the EPGFZ, a component of fault-normal convergence in addition to the main strike-slip motion. The magnitude of this fault-normal component varies between the models depending on the geometry of the blocks and the data set, but suggests significant transpression on the EPGFZ.…”