SEMINAR: GEOTOPICS: Dr. Shimon Wdowinski (9/13 3:15pm)

[Qiong Zhang <qzhang@rsmas.miami.edu>]

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 P  r  e  s  e  n  t  s  

3:15 PM, Monday,September 13th, 2010
SLAB Seminar Room, S/A 103

Refreshments 3:00 PM

Shimon Wdowinski

Research Associate Professor

RSMAS-MGG

swdowinski@rsmas.miami.edu

              "

Hurricanes and possibly deforestation as triggers the 2010 Haiti earthquake"

The January 12^th, 2010, M = 7.0 Haiti earthquake was one of the worst natural disasters of the past century. This devastating earthquake caused the death of more than 200,000 people, the injury of about 300,000 people, and left about two million people homeless. Just a year and a half prior to the earthquake, Haiti was subjected to another severe disaster, flooding induced by two hurricanes and two tropical storms (Fay, Gustav, Hanna and Ike). Both natural disasters results in death and destruction, but because their origins are very different, they are generally considered to be unrelated phenomena. We suggest a physical link between these two destructive events, in which the 2010 Haiti earthquake was triggered by rapid erosion induced by hurricane activity. The suggested denudation triggering mechanism is consistent with seismic and geodetic analysis on the earthquake rupture, indicating an initial oblique motion on a southward dipping fault followed by intense reverse faulting on a northward dipping fault (Hayes et al., 2010).

Our triggering analysis is based on interdisciplinary research using satellite imagery, bathymetric charts, detailed DEM, and 3-D mesh-free finite element modeling. Remote sensing analysis of the nearby Leogane Delta’s growth over the past 35 years indicates a rapid delta build up due to a mean erosion rate of 6 mm/yr. Theoretical calculations based on finite element modeling and Coulomb failure stress criterion suggest that denudation-induced stress changes at the hypocenter reached the earthquake’s triggering threshold (3 kPa) after 60-80 years at the present day erosion rate. Our results also suggest that the rapid sediment deposition in the delta kept clamping the northward dipping fault allowing a continuous stress build up on the fault, which explains the large amount of seismic energy released by this fault during the earthquake. Haiti’s massive deforestation most likely contributed to the rapid erosion in the past several decades and the heavy tropical rains contribute to efficient sediment transport. The heavy rain poured during the 2008 hurricane season flushed the drainage system in the epicenter area and removed the last significant sediment load that triggered the 2010 Haiti earthquake.

Qiong Zhang

Marine Geology and Geophysics
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami Fl 33149