RAPID: Collaborative Research: Off-shore coseismic effects of the Port au Prince earthquake, Haiti (University of Texas at Austin)
Scientists have discovered underwater evidence that Haiti's unusual 2010 earthquake may not have been the first of its kind in the region. They took core samples from the seafloor that reveal a 2000-year-old sequence of sediment layers closely resembling landslide deposits triggered by the 2010 quake, indicating an older event of similar violence and other characteristics.
The 2010 magnitude-7.0 earthquake was catastrophic for Haiti, causing about 230,000 casualties and devastating the capital and surroundings. Understanding the timing and behavior of major earthquakes like this one is crucial for protecting people and infrastructure around active fault zones.
The Enriquillo-Plantain-Garden fault zone (EPGF), where the 2010 earthquake occurred, is part of the boundary between the North American and Caribbean tectonic plates. This is a strike-slip fault, in which the two plates typically slide past one another horizontally. However, during the 2010 earthquake, the plates also appear to have been thrusting towards one another, causing uplift in some places and subsidence in others as the land surface compressed. The EPG fault zone continues offshore, so a multidisciplinary marine research team was rapidly organized after the quake. Researchers and students from the U.S. and Haiti sailed in the R/V Endeavor, using sound-based technology to search the seafloor for areas affected by the quake.
Cores collected in these areas led to the discovery of the older, analogous event. The ~2000-year gap between this older event and the 2010 quake indicates a form of tectonic activity atypical for the EPGF, where earthquakes generally occur about 250 years apart. This suggests that the unusual thrusting motion associated with the devastating 2010 earthquake may have also been at work 2000 years ago.
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