Faulting Processes of Historic (1917–1962) M≥ 6.0 Earthquakes Along the North-central Caribbean Margin

Abstract

The plate boundary along the north-central Caribbean margin is geologically complex. Our understanding of this complexity is hampered by the fact that plate motions are relatively slow (1 to 2 cm/yr), so that recent seismicity often does not provide a complete picture of tectonic deformation. Studies of the faulting processes of instrumentally recorded earthquakes occurring prior to 1962 thus provide important information regarding the nature and rate of seismic deformation within the region, and are essential for a comprehensive assessment of seismic hazard. We have conducted body waveform modeling studies of eight earthquakes which occurred along the north-central Caribbean plate margin, extending from southeastern Cuba to the Swan Island fracture zone (75 to 83°W). None of these earthquakes has been previously studied and several occurred in regions where no recent (post-1962) seismicity has been recorded. The plate margin in the western portion of our study area is characterized by a transform fault-spreading center system. In the central and eastern portions of our study area the plate margin is a complex, diffuse region of deformation that couples transform motion in the Cayman trough to subduction along the Lesser Antilles arc. Our results show that the western portion of the study area has only experienced large strike-slip earthquakes. Off southeastern Cuba two earthquakes appear to have occurred on high angle, northward dipping, reverse faults with south to southeastward directed slip vectors. An earthquake in northern Jamaica in 1957 shows pure strike-slip faulting, most likely along an east-west trending fault. Finally, an unusual sequence of events located in the Pedro Bank region 70 km southwest of Jamaica has a mainshock with a reverse-oblique mechanism, suggesting continuity of the plate interface stress field well south of the northern Caribbean margin.

Crustal velocity model along the southern Cuban margin: implications for the tectonic regime at an active plate boundary

“…It has been suggested that most of the stress accumulated by the Caribbean–North American plate motion is released seismically along the northern Cuban margin during a relatively few but strong earthquakes (Perrot et al 1997; Van Dusen & Doser 2000). This sparse occurrence of strong and moderate earthquakes makes it difficult to use earthquake focal mechanisms for mapping the crustal stress field in this area.…”

Current block motions and strain accumulation on active faults in the Caribbean

“…At the northeastern edge of the study area (Figure ), the Oriente fault bounds the Cayman trough, a 45–50 Ma oceanic pull apart basin [ Rosencrantz et al , ], to the north. Earthquake focal mechanisms show pure left‐lateral strike‐slip motion from the mid‐Cayman spreading center to the southern Cuban margin [ Perrot et al , ] where the fault trace slightly changes direction to become transpressional [ Calais and de Lepinay , ], with earthquake focal mechanisms showing a combination of thrust and strike‐slip faulting [ Van Dusen and Doser , ]. To the east, the Oriente fault pursues its course through the Windward Passage, along the northern Haitian coast as the “Septentrional fault” [ Calais and de Lépinay , ], then farther east on land through the Cibao Valley of the Dominican Republic [ Calais and de Lépinay , ] where paleoseimological studies indicate a Holocene slip rate of 9±3 mm/yr [ Prentice et al , ], in agreement with GPS estimates [ Calais et al , ].…”

Seismotectonics of Jamaica

“…1) whose historic record of earthquakes dates back more than 300 yr. Most notable are: the 1692 Port Royal earthquake whose magnitude could have been as high as 8 (Clarke 1995); the 1907 Kingston earthquake whose magnitude was Ms 6.5 (Pereira 1977); and the 1957 Montego Bay event with a recalculated magnitude of Mw 6.9 (Van Dusen & Doser 2000). The epicentre of the 1957 event was relocated from an initial offshore locality to fall on land in NW Jamaica (Fig.…”

“…The polar plot shows stress regime in the area outlined by dashes: diamond =σ 1 = azimuth 254°/plunge 16°; circle =σ 2 = 348°/12°; triangle =σ 3 = 113°/70°, where σ 1 is the maximum compressive stress (Moreno et al 2002). Fault plane solutions A—G with pressure axes (dots) and slip directions (small arrows) are based on waveform modelling (Van Dusen & Doser 2000); I and H are Harvard CMT fault plane solutions for recent moderate (Mw 5.5) Jamaica earthquakes of 1988 Novermber 12 and 1993 January 13, respectively. Arrows with accompanying numbers are estimates of slip in mm yr −1 from GPS measurements given for the Caribbean Plate interior and tangential and normal to the OFZ near southeastern Cuba (De Mets et al 2000) and for Hispaniola (Mann et al 2002).…”

“…They also resolved movement along the OFZ off southeastern Cuba into 18–20 (±1) mm yr −1 along the fault and 3 (±2.5) mm yr −1 of convergence. Van Dusen & Doser (2000) through body‐waveform modelling of larger pre‐1963 earthquakes (A to G in Fig. 1) estimated that up to 90 per cent of the plate boundary slip is accommodated on the OFZ and only 10 per cent on the WFZ.…”