Spatial Characterization of the Isla de Mona Fault in the NE Caribbean from High-Resolution Topography

Daniel Laó-Dávila, Oklahoma State University
Eric Lebar, Oklahoma State University

Abstract

The Isla de Mona Fault is the only mapped fault on Mona Island, an uninhabited aerially exposed carbonate platform between Hispaniola and Puerto Rico in the Northeastern Caribbean. The fault is considered a normal fault caused by extension in the Mona Passage between Puerto Rico and Hispaniola. Extension in the Mona Passage has been confirmed by bathymetric and seismic surveys that characterized faults of the Mona Rift and a predominantly WNW-ESE and NW-SE striking normal faults to the north of Mona Island. However, the 30-50 m resolution of the bathymetry does not allow for detailed observations of fault spatial characteristics to occur. We used a 1-m high-resolution bare-earth digital elevation model (DEM) derived from lidar dataset collected by the U.S. Geological Survey in 2017 to unravel the spatial characteristics of the Isla de Mona Fault and its implication for seismic hazard. The DEM was analyzed in QGIS using Hillshade, Aspect, Slope, and Roughness maps to find the contacts of the carbonate layers and the fracture scarps. While lithological contacts have broad scarps and roughly follow the topographic contours due to gentle dips, fracture scarps are sublinear and cut lithological contacts. We created topographic profiles perpendicular to the scarps to help us interpret their origin. We then quantified the change of fault scarp height along the strike of the faults. Results show that the Isla de Mona Fault is a fault zone that in the south, a segment strikes NW-SE and connects to a N-S striking segment in the north. In the area of intersection, the fault forms a basin where the underlying dolomite is exposed. The southern segment has the highest scarp height of 17 m that decreases to ~ 2 m at the tips. The northern segment has a maximum scarp height of 4 m that decreases to the north. The fault tip of the southern segment consists of a distributed fault splay. Observations of the karst topography indicate that sinkholes preferentially form along fractured areas and that alignment of these suggest a regional joint pattern striking NE-SW in the NE of the island. We conclude that the Isla de Mona Fault is an expression of a growing fault formed by segments that reflect the strain partitioning of oblique rifting accommodated in the Mona Passage. The linkage to a submarine fault mapped in the bathymetry suggests that the fault represents the propagation of a 12 km-long potentially seismogenic fault.

Session

Neotectonics
earthquake geology