The January 12th,
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.
