A RAPID response
The US National Science Foundation funded an NSF-EAR RAPID proposal
(E. Calais, PI) for an integrated geodetic, geologic, and remote
sensing field response to the January 12, 2010, Mw 7.0 earthquake in
Haiti. The work is supported by the Geophysics Program (GEO/EAR) and
the Americas Program in the NSF Office of International Science and
Engineering (OISE). Technical support is provided by UNAVCO. Trimble,
Inc., donated 6 sets of GPS erquipment to the project. Voila provided
logistical support, safe locations and data communication for the
continuous GPS instruments. The Bureau of Mines and Energy (BME), the
National Center for Geospatial Information (CNIGS), the National
Observatory for the Environment and Vulnerability (ONEV), the State
University / School of Science (UEH/FDS), the Civil Protection AGency
(DPC) provided essential collaboration and support.
The field work included:
- Searching for, and possibly mapping, the surface rupture of the
01/12 event to help constrain a detailed slip distribution model. This
work is coordinated by Paul Mann (Univ. of Texas, Austin), with the
field assistance of Richard Koehler (Alaska Geological Survey) and
performed in collaboration with imagery analysis by Carol Prentice
(USGS Menlo Park). Preliminary results show that the earthquake rupture
did not reach the surface, consistent with a slip inversion from radar
interferometry data. Observations along the coastlines show subsidence
in the area of Petit and Grand Goave (from sunken beaches) and uplift
in the area of Legogane (from emerged coral heads), consistent with
radar interferometry data. These observations corroborate those made by
R. Bilham (Univ. Colorado) and W. Mooney (USGS). Historical accounts of
the 1751 earthquake show a remarkable similarity in the areas of
coastline subsidence along the Leogane to Petit Goave
- Surveying with GPS 30 geodetic benchmarks previously occupied in
Haiti between 2003-2009 (E. Calais, A. Freed, G. Mattioli). These sites
were the basis for a tectonic block model that showed ~7 mm/yr of
interseismic strain accumulation on the EPGFZ. A new survey will
provide 3D coseismic displacements that, together with geological
mapping and radar interferometry will help determine the earthquake
slip distribution. A total of 35 sites have been surveyed for 2 to 4
days each. All the sites located in the epicentral area have been
recovered; only one site has been destroyed (Montrouis).
- Installing 6 continuously operating GPS stations to measure
postseismic deformation processes, study interseismic strain
accumulation, and possibly capture coseismic deformations from
earthquakes to come. All stations are installed and operating.
Locations are: Canape Vert (Port au Prince), Roussette (St Marc),
Leogane, Petit Goave, Les Cayes, Jacmel. Data is open and made
available via UNAVCO (www.unavco.org).
- Complementing the field effort by computing coseismic
interferograms from radar data. This work is coordinated by Falk
Amelung (Univ. Miami). Preliminary results from ALOS data (Japanese
Space Agency) shows that coseismic deformation is concentrated between
Carrefour and Petit Goave. First calculations indicate that the range
change data is consistent with a combination of left-lateral strike
slip and thrust motion on at least one north-dipping fault. The source
appears quite compact, with up to 4 m of slip right under the eastern
edge of the Leogane alluvial fan. This main be a zone of
transpressional parallel to the main trace of the EPGFZ as recognized
in a PhD dissertation by R. de Momplaisir in 1985.
In addition to the items described above, several other scientific
efforts have taken place since the earthquake:
- LIDAR acquisition of a segment of the Enriquillo fault and of the
Port au Prince area. PI Jan van Aardt, Rochester Inst of Technology.
- Structural engineering evaluation. EERI/USGS team led by
Marc Eberhard, Univ of Washington.
- Engineering geology and liquefaction effects, NSF/GEER team
led by Ellen Rathje, Dept of Engineering, Univ of Texas at Austin.
- Earthquake Engineering Research Institute (EERI) Reconnaissance Trip,
team leader Reginald DesRoches, Georgia Institute of Technology.
- Deployment of 20 Ocean Bottom Seismometers, French R/V Atalante,
Chief Scientist Bernard Mercier de Lepinay, CNRS Sophia Antipolis.
- Installation of 5 on-land seismic stations, led by Yves Mazabraud
- Installation of seismic stations and accelerometers, U.S. Geological
Survey team led by Sue Hough.
- R/V Endeavor offshore survey, chief scientist Cecelia McHugh,
LDEO and CUNY.