Neotectonic structures and stress fields associated with oblique collision and forearc sliver formation in northern Hispaniola: Implications for the seismic hazard assessment

摘要

Active oblique collision between the Caribbean and North America plates has led to the formation of the Septentrional forearc sliver, which is a wedge-shaped crustal domain limited to the north by the North Hispaniola subduction thrust and to the south by the Septentrional Fault Zone (SFZ). In northern Hispaniola, oblique collision of the Bahamas Platform began in the uppermost Pliocene to Early Pleistocene and continues today. Collision-related tectono-stratigraphic processes include destruction of the shallow-water carbonate forearc platform, uplift and erosion of the Cordillera Septentrional and Samand Peninsula, emergence of the Cibao Basin and syn-tectonic deposition of alluvial fan systems. The geometry and kinematics of neotectonics structures at all scales, together with stress field solutions obtained from late Cenozoic fault-slip data, show that the ENE-directed (far-) stress field associated with collision triggered the formation of the WNW-trending, left-lateral strike-slip SFZ. The SFZ thus represents the inland, concave master fault bounding the Septentrional forearc sliver. Subsidiary ENE to NE-trending left-lateral strike-slip faults (R-type) and NNE to NE-trending normal and oblique faults (T-type) controlled the internal deformation and subdivision into smaller tectonic blocks of the sliver. The highly oblique convergence and the increase in frictional plate coupling associated with the underthrusting of the Bahamas Platform are the likely causes of the formation of this forearc sliver. In the Western Cordillera Septentrional and Cibao Basin, an extensional regime is locally produced by the transfer of the left-lateral movement to a southern splay of the SFZ with the incorporation of a detached block to the Septentrional forearc sliver during the Middle Pleistocene-Holocene. The regional distribution of the modeled Peak Ground Acceleration values indicates that the SFZ is the greatest seismic hazard in northern Hispaniola.