Crustal structure and fault geometry of the 2010 Haiti earthquake from temporary seismometer deployments

TitleCrustal structure and fault geometry of the 2010 Haiti earthquake from temporary seismometer deployments
Publication TypeJournal Article
Year of Publication2013
AuthorsDouilly R., Haase JS, Ellsworth W.L, Bouin M.P, Calais E, Symithe S.J, Armbruster J.G, de Lepinay B.M, Deschamps A., Mildor S.L, Meremonte M.E, Hough S.E
JournalBulletin of the Seismological Society of America
Date Published2013/08
Type of ArticleArticle
ISBN Number0037-1106
Accession NumberWOS:000322569200013
Keywordsaftershock sequence; california; deformation; hayward fault; least-squares; loma-prieta earthquake; main shock; model; plate boundary; seismic hazard; velocity

Haiti has been the locus of a number of large and damaging historical earthquakes. The recent 12 January 2010 M-w 7.0 earthquake affected cities that were largely unprepared, which resulted in tremendous losses. It was initially assumed that the earthquake ruptured the Enriquillo Plantain Garden fault (EPGF), a major active structure in southern Haiti, known from geodetic measurements and its geomorphic expression to be capable of producing M 7 or larger earthquakes. Global Positioning Systems (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data, however, showed that the event ruptured a previously unmapped fault, the Leogane fault, a north-dipping oblique transpressional fault located immediately north of the EPGF. Following the earthquake, several groups installed temporary seismic stations to record aftershocks, including ocean-bottom seismometers on either side of the EPGF. We use data from the complete set of stations deployed after the event, on land and offshore, to relocate all aftershocks from 10 February to 24 June 2010, determine a 1D regional crustal velocity model, and calculate focal mechanisms. The aftershock locations from the combined dataset clearly delineate the Leogane fault, with a geometry close to that inferred from geodetic data. Its strike and dip closely agree with the global centroid moment tensor solution of the mainshock but with a steeper dip than inferred from previous finite fault inversions. The aftershocks also delineate a structure with shallower southward dip offshore and to the west of the rupture zone, which could indicate triggered seismicity on the offshore Trois Baies reverse fault. We use first-motion focal mechanisms to clarify the relationship of the fault geometry to the triggered aftershocks.

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