Preliminary results of the along- and across-strike crustal structure in the northern Hispaniola margin

Abstract

The North American plate converges with the Caribbean plate at a rate of 20.0 . 0.4 mm/yr. towards 254 . 1.. Convergence is highly oblique to the plate boundary (10-20.), resulting in along-strike segmentation, strain partitioning and microplate tectonics. Series of large to great shallow earthquakes occurred in the northern Hispaniola margin in last two centuries. These earthquakes have been attributed to the underthrusting/collision of the relatively thick continental crust of the Carbonate Bahamas Banks beneath/with the Caribbean plate and to the left-lateral strike-slip motion along the Septentrional-Oriente fault zone. Seismic activity along the margin included the M8.0 historical event of 1842, four M>7.0 earthquakes between 1943-1953, including an Ms 8.1 tsunamigenic event in 1946, and a Mw 6.4 event in 2003. From 2005 to 2014 significant efforts were carried out to elucidate the crustal structure of the northern Hispaniola margin. An international collaborative research, leaded by the Universidad Complutense of Madrid, the Sorbonne Universit., the Institut Fran.ais du P.trole-Energie Nouvelles and the U.S. Geological Survey, carried out five geophysical cruises exploring the 500 km-long northern Hispaniola margin, from their western end in the Windward Passage to the eastern end in the Mona Passage. Cruises collected systematic high-resolution swath bathymetry, high-resolution seismic data, multichannel seismic reflection profiles and continuous gravity and magnetic data. In this study we show preliminary results based on the combined interpretation of the new and old reprocessed data of the shallower structure of the northern Hispaniola margin. This margin can be divided into three main morphotectonic provinces: The Bahama Banks, the Hispaniola Trench and the Insular Margin. We study how these three provinces show the east-to-west transition from the highly oblique subduction in the Puerto Rico trench, to the oblique collision in the northeastern Hispaniola, and to the oblique underthrusting in the north-northwestern Hispaniola. The Insular Margin Province gathers most of active compression features being characterized by an along-strike segmented north-verging compressive system built by series of active fault-propagation folds. Some of these faults seems to be deep-rooted structures that could be involved in the earthquake nucleation. These preliminary results and further interpretation of active deformational features will provide valuable information for the earthquake and tsunami assessment in the northern Hispaniola.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018