USGS invests in geologic mapping, landslide hazard research throughout Peurto Rico
The $1.1 million project is funded through the 2023 Disaster Relief Supplemental Appropriations Act. Aerial surveys will map the geologic landscape with the goal of better understanding natural hazards and identifying surface materials that could be used to build and enhance hazard-resilient infrastructure.
The research was conducted through a combination of lower altitude (approximately 11,000 feet) flights that collected data from reflected sunlight at a very fine resolution over three regions: western Puerto Rico in the vicinity of the city of Mayaguez, southern Puerto Rico in the vicinity of Ponce, and the Central mountains near Jayuya.
The sensors aboard the aircraft recorded both reflected solar radiation from the visible to near-infrared and shortwave infrared wavelengths and thermal emissions at longer infrared wavelengths. Combined, these sensors are termed hyperspectral because they span the electromagnetic spectrum. This allows researchers to distinguish among various surface materials, including different rock, soil, and vegetation types due their unique reflectance characteristics or “spectral signatures.”
“Looking for these patterns, or spectral signatures, can help identify locations with high potential for mineral resources and allow us to map landslide source areas and study vegetation recovery in these areas,” said Bernard Hubbard, a USGS research geologist with the Geology, Energy and Minerals (GEM) Science Center in Reston, Virginia.
Particular areas of interest for the surveys included regions affected by landslides following hurricanes Maria and Fiona; the island’s only exposed limestone quarries; several cement-producing plants for industrial minerals and building materials such as quartz sand and gravel; and other critical minerals that are necessary for post-hurricane reconstruction and building of homes and businesses, as well as future storm resiliency.
The USGS also collaborated with the University of Puerto Rico. At the Rio Piedras campus, Dr. Carla Restrepo, a professor of Biology at the University’s College of Natural Resources, will use these data to examine ways in which organisms influence landslide formation.
“Specifically, the hyperspectral data may help identifying vegetation covers that better protect slopes from failure,” said Restrepo. “These data may aid characterizing conditions that favor microbial weathering, that is the process by which microorganisms contribute to the decomposition of rocks.
Originally developed by NASA, hyperspectral imaging has a long history of use in mineral, natural hazard and ecological research. The USGS and NASA have previously collaborated on collecting and analyzing hyperspectral data, including the 17-year Earth Observing-1 mission.
These data points are also useful for understanding a variety of other earth-science and biological issues including acid mine drainage, debris flows, agriculture, wildfires and biodiversity. The USGS has since used these methods to collect data and produce geologic maps throughout the country including Alaska and the Greater Antilles.