ARLINGTON - A new study co-authored by UT Arlington College of Science Dean Pamela Jansma,
earth and environmental sciences professor Glen Mattioli and researchers at
several other universities presents strong evidence that the Jan. 12 Haitian
earthquake was caused by a previously unmapped fault and not one experts first suspected.
researchers say “a significant seismic threat for Haiti and for Port-au-Prince
in particular” remains because the earthquake didn’t release significant
accumulated strain from the Enriquillo-Plantain Garden fault, as first believed.
Their paper, “Transpressional rupture of an unmapped fault during the 2010
Haiti earthquake,” will be published in the November issue of the journal
Nature Geoscience and is already available online.
researchers concluded that a previously unmapped fault called the Léogâne fault
caused the quake.
Calais, a Purdue University professor of earth and atmospheric sciences, led
the research team, which also included experts from University of Miami and
institutions in Saudi Arabia and Haiti. Calais, Jansma and Mattioli have worked
together since the mid-1990s and data for the current study was obtained, in
part, from their 2004 National Science Foundation funded study of surface
deformation and seismic activity on the island of Hispaniola, which includes
Haiti and Dominican Republic.
who traveled to Haiti on Jan. 29 to gather data with Calais, said the latest
results add new dimension to scientists’ understanding of the area where the
Caribbean and North American tectonic plates meet.
because there was a magnitude seven quake that happened on this Léogâne fault
doesn’t necessarily mean the risk is diminished on the Enriquillo-Plantain
Garden fault, especially to the east and the west of the rupture zone,” said
Mattioli. “Ultimately, there’s going to be more earthquakes in this region of
the world, and the fact is we don’t have a lot of good information about how
frequently these faults rupture.”
than 200,000 people died in the Jan. 12 quake. Damage has been estimated at
more than $8 billion. Originally, researchers thought the quake was due to a
rupture on the Enriquillo-Plantain Garden fault, which extends from western
Dominican Republic to beyond the western tip of the Tiburon-peninsula of Haiti,
passing near major population centers of Port-au-Prince and Léogâne. To explore that idea, Calais’ team used
global positioning system observations and radar interferometry measurements of
scientists found that instead of moving the ground east to west, as they
believed a quake from the Enriquillo-Plantain Garden fault would, the quake had
actually moved the ground toward the fault and upward, causing shortening of
the ground surface in the region near the earthquake, Mattioli said. Those
measurements, along with data about the location of the quake, led them to
believe a rupture of the Enriquillo-Plantain Garden fault had not occurred.
Calais and his team inferred that the Jan. 12 quake actually resulted from a
rupture on an unmapped north-dipping fault they called the Léogâne fault. That
fault is subparallel to the Enriquillo-Plantain Garden fault, researchers
Léogâne fault is what is known as a “blind thrust” because the fault does not
reach to the surface and can’t therefore be seen, said Jansma, who is an expert
in tectonics of the northern and eastern Caribbean.
thrust is the type of fault on which the Northridge earthquake in southern California
occurred in 1994. These faults are known to exist, but difficult to
detect,” Jansma said. “This is particularly the case in places like Haiti
where the detailed mapping and subsurface investigation haven’t been done to
the same extent as other places, such as southern California.”
a story from the Purdue University news service earlier this week, Calais said
the new paper highlights the need for more exploration of the fault system in Hispaniola.
fault system is more complex than we originally thought, and we don't yet know
how the January earthquake impacted the other faults,” Calais said.
“Preliminary measurements indicate that the Enriquillo fault did not release
any accumulated seismic energy and, therefore, remains a significant threat for
Haiti, and Port-au-Prince in particular."
added that the “inexorable” earthquake risk in Haiti should be motivation for a
focus on proactive measures to adapt to earthquake hazards and save lives.
latest research was supported by grants from the National Science Foundation
and the National Disaster Risk Management System Development Program – UNDP
Jansma’s work is representative of the research under way at The University of Texas at Arlington, a comprehensive undergraduate
and graduate institution of nearly 33,000 students in the heart of North Texas.
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