Crustal thickness and bulk Poisson ratios in the Dominican Republic from receiver function analysis

Abstract

The Dominican Republic (DR) comprises the eastern two-thirds of the island of Hispaniola, which is located on the Caribbean-North American plate boundary. Previous studies have described the shallow structure and stratigraphy of the island but, due to a dearth of broadband seismic data, little is known about the lower crust and mantle. Since August 2014, thirteen broadband, three-component seismic stations have been deployed temporarily in the DR. They are combined with four permanent broadband stations in the DR and three in neighboring Haiti to enhance studies of Hispaniola's lower crust and upper mantle. We report results of a receiver function study using teleseismic data recorded by these stations. Specifically, we compute receiver functions and determine crustal properties via H-κ stacking. We propose additional intracrustal and upper mantle layers based on identifications of prominent and coherent P-to-S converted phases observed in receiver function gathers. Our results show that crustal thickness varies beneath the island of Hispaniola over the range 13–47 km with a median of 24 km and bulk Vp/Vs ratios vary over 1.58–1.99 with median 1.79. Receiver function modeling reveals intracrustal discontinuities at station PAPH (Port au Prince, Haiti), at a depth of 8.0 km, station JIDR (Jimaní, DR; 8.8 km depth), and SDDR (Sabaneta, DR; 15.8 km depth). Additional discontinuities appear in the upper mantle beneath PAPH (60.1 km depth), PCDR (Punta Cana; 60 km), SDD (Santo Domingo; 70 km), and SC01 (Santiago; 81 km). Two north-south cross-sections show variations in bulk Vp/Vs ratios that are consistent with expectations based upon surface geology but variations in crustal thickness are more scattered and do not conform to expectations from simple tectonic models of Hispaniola's formation. Our stacking results reveal consistency between Vp/Vs ratios in four distinct regions which are consistent with the compositional domains identified by previous studies.