Is there a northern Lesser Antilles forearc block?

Abstract

A systematic discrepancy exists between slip vectors of thrust fault earthquakes at the Lesser Antilles trench (LAT) and the predicted direction of North American‐Caribbean convergence. A possibility has been that the discrepancy resulted because neither was well constrained. Estimating Caribbean motion has been challenging owing to the limited data along the plate's complex boundaries. Similarly, earlier studies had few slip vectors because interplate thrust events are infrequent. To address these difficulties, we estimate a new Caribbean‐North America Euler vector using recently available GPS data from sites in the presumably stable interior of the Caribbean, and compare the predicted velocities to a larger set of slip vectors. The discrepancy persists, suggesting the northern Lesser Antilles forearc (NLAF) moves as a distinct entity from both the Caribbean and North America. For simplicity, we treat its motion as a coherent block, but because GPS sites are not within the NLAF, distributed deformation is also possible. Although there is no geologic evidence for the boundaries of the presumed NLAF block, GPS data show that the motions of Martinique, Barbados, and Trinidad are similar to that of the Caribbean, suggesting that none are on the NLAF block, and the southern LAT is weakly coupled.

Chapter 1 An overview of the eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010

“…Drilling in 2012 through about 130 m of marine sediment, around 60 km SW of Montserrat (IODP Expedition 340 Scientists 2012), revealed tephra layers from much of the approximately 5 Ma record there, but their provenance is not yet certain. The southerly migration of the locus of volcanism (Silver Hills, c. 2 Ma; Centre Hills, c. 1 Ma; SHV, ,0.25 Ma) occurred at about 5 mm a 21 , compatible with the predicted rate of Caribbean plate extension in this region of about 6 mm a 21 (Lopez et al 2006). Silver Hills and Centre Hills are surrounded by distinct submarine shelves about 5 km wide and as deep as 60-100 m (mainly 20 -60 m) below sea level ( Fig.…”

“…1.1). This can be accommodated by north -south extension of this part of the Caribbean plate (Lopez et al 2006). There is contemporary evidence for such extension from seismicity and geological evidence from roughly east -west normal faulting (Feuillet et al 2002(Feuillet et al , 2010Kenedi et al 2010).…”

Geomorphic and stratigraphic evidence for an unusual tsunami or storm a few centuries ago at Anegada, British Virgin Islands

“…1a). The interplate motion, averaging two meters per century, is nearly parallel to the trench (López 2006). GPS measurements from 1994 to 2005 provide evidence for negligible coupling between the plates north of Puerto Rico but roughly 50 percent coupling northeast and east of Anegada (Manaker 2008).…”

Identification of deep subaqueous co-seismic scarps through specific coeval sedimentation in Lesser Antilles: implication for seismic hazard

“…The Lesser Antilles volcanic arc results from the convergence between the Caribbean and American plates at a rate of about 2 cm yr −1 (Minster and Jordan, 1978;Demets et al, 2000;Lopez et al, 2006) (Fig. 1).…”