Caribbean Tsunami and Earthquake Hazards

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Four million U.S. citizens live along the coastlines of Puerto Rico and the U.S. Virgin Islands, an earthquake- and tsunami-prone active tectonic plate boundary. A tsunami generated at the subduction zone boundary offshore Puerto Rico could also affect the U.S. Atlantic coast.

person standing next to large boulder

A brain coral boulder eight feet in diameter stands 750 feet inland in the British Virgin Islands. Geologists say that the coral was brought ashore, probably alive, by an unusual tsunami or storm between the years 1200 and 1480. Credit: Brian F. Atwater, USGS 

Following the devastating 2004 Indian Ocean tsunami, the CMHRP launched a Caribbean Tsunami and Earthquake Hazards study to focus on hazards in this region. CMHRP partners in the United States (NOAA, University of Puerto Rico-Mayaguez) and in Spain provided support to advance this effort.

To better understand Caribbean tsunami and earthquake hazards, the CMHRP investigated past earthquakes, tsunamis, and seafloor landslides; recorded active earthquake tremors to infer their cause; and used numerical modeling to locate faults and determine whether stress might be accumulating on them. The CMHRP mapped or compiled existing seafloor bathymetric data (i.e., ocean depth data) over a 200,000 square kilometer area, supplementing these data with seismic reflection profiles (which are like taking a CAT scans of the seafloor but use sound instead of X-rays), interpretations of seafloor structure and tectonics, and direct sampling of submarine landslide deposits to determine their age. Mapping of onshore tsunami deposits was used to further constrain the age and impact of tsunamis from both local and far-field sources. Modeling of the 1867 and 1918 tsunami allowed identification of the source locations for these events and provides insight about future hazards. Sensitive ocean bottom seismometers recorded contemporary tremors, while quantitative analyses have been applied to damage patterns from historical earthquakes to estimate the location and magnitude of these events.

In the future, a more regional approach that includes not only the Virgin Islands and Puerto Rico, but also Cuba, Haiti, and the Lesser Antilles, could facilitate substantial breakthroughs in assessing seismic and tsunami hazards in this tectonically active area.

Topography and bathymetry map of the Northeastern Caribbean.

Earthquake locations from historical analysis of earthquakes and modern epicenters of moderate and large earthquakes. Recurrence intervals for earthquakes in different tectonic regions are marked in red lines. Those parts of the subduction zone without red lines are not expected to generate large earthquakes. Credit: USGS