Coseismic slip distribution of the 2010 m7.0 Haiti earthquake and resulting stress changes on regional faults
Abstract
The Mw 7.0 January 12, 2010, Haiti earthquake ruptured the previously unmapped Léogâne Fault, a secondary transpressional fault located close to the Enriquillo Plantain Garden Fault (EPGF), the major fault system assumed to be the primary source of seismic hazard for southern Haiti. In the absence of a precise aftershock catalog, previous estimations of coseismic slip had to infer the rupture geometry from geodetic and/or seismological data. Here we use a catalog of precisely relocated aftershocks covering the 6 months following the event to constrain the rupture geometry, estimate a slip distribution from an inversion of GPS, InSAR and coastal uplift data, and calculate the resulting changes of Coulomb failure stress on neighboring faults. The relocated aftershocks confirm a north dipping structure consistent with the Léogâne fault, as inferred from previous slip inversions. Our updated source model involves two subfaults, each corresponding to a major slip patch. The eastern one combines strike-slip and dip-slip, while the western one is mostly strike-slip. Overall, the event released 68 % of left-lateral strike-slip and 32 % of dip-slip reverse seismic moment, consistent with secular strain accumulation in southern Haiti from regional GPS studies. Coulomb failure stress changes caused by the coseismic rupture show that the cluster of reverse faulting earthquakes, one as large as M 5.9, that were observed to the west of the coseismic rupture coincident with the offshore Trois Baies fault were likely triggered by the main shock. We find increased stresses on the Enriquillo fault to the west of the January 12, 2010 rupture (Miragoâne area, ∼3 bars) and to the east near Port-au-Prince (0.3 to ∼1 bar). Other regional faults do not show significant increase of static stresses at seismogenic depth. Increased coseismic stress changes on the Trois Baies fault and portions of the Enriquillo fault to the west and east of the Léogâne rupture are a concern as this could advance the timing of future events on those faults, which are all capable of magnitude 7 or greater events.
Degree
M.S.
Advisors
Calais, Purdue University.
Subject Area
Geophysics
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