Initial Seismic Hazard Maps for Haiti


Arthur Frankel, Stephen Harmsen, Charles Mueller, Eric Calais, and Jenifer Haase
USGS Open File Report 2010-1067

In response to the urgent need for earthquake hazard information after the tragic disaster caused by the M7.0 January 12, 2010 earthquake, we have constructed initial probabilistic seismic hazard maps for Haiti. These maps are based on the current information we have on fault slip rates and historical and instrumental seismicity. These initial maps will be revised and improved using more extensive logic trees and incorporating new information on fault parameters and previous large earthquakes as they become available.

The general methodology used here was developed for the 1996 U.S. national seismic hazard maps and also implemented in the 2002 and 2008 updates (Frankel et al., 2000; Petersen et al., 2008). This procedure uses fault slip rates derived from GPS measurements (Manaker et al., 2008), spatially-smoothed seismicity for shallow earthquakes and Benioff-zone earthquakes, assumptions on fault segmentation, and attenuation relations. For the later, we used the relations applied in the western portion of the 2008 version of the U.S. national seismic hazard maps (Petersen et al., 2008). The lack of information on Haiti faults requires many assumptions to be made. These assumptions will need to be revisited and re-evaluated as more data become available.

These seismic hazard maps are important for the management of the current crisis and the development of building codes and standards for the rebuilding effort. However, we stress that these new maps do not consider all the sources of earthquake hazard that affect the Hispaniola and should not be considered as complete hazard maps, in particular for eastern Hispaniola.



Crustal faults and subduction zones used in the hazard maps. Red lines are the portions of the Septentional and Enriquillo faults used to calculate Mchar and whose predicted earthquake rates are shown in Table 1. Green lines are the western portions of the Septentrional and Enriquillo faults that are treated separately. Blue are the traces of the uppermost portion of the subduction zones considered. Inferred segment boundaries used in the maps are also shown.

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Seismic hazard map with peak ground acceleration (PGA; in %g) with 10% probability of exceedance in 50 years, without aftershock hazard.

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Seismic hazard map with PGA (%g) with 2% probability of exceedance in 50 years (1 in 2500 annual probability of exceedance), without aftershock hazard.

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Seismic hazard maps using site amplification based on Vs30 values derived from topographic slope (David Wald, written comm., 2010). Maps show PGA with (top) 10% and (bottom) 2% probabilities of exceedance in 50 years (without aftershock hazard).

References:

Frankel, A., C. Mueller, T. Barnhard, E. Leyendecker, R. Wesson, S. Harmsen, F. Klein, D. Perkins, N. Dickman, S. Hanson, and M. Hopper, 2000, USGS national seismic hazard maps, Earthquake Spectra, v. 16, pp. 1-19.

Manaker, D.M., Calais, E., Freed, A.M., Ali, S.T., Przybylski, P., Mattioli, G., Jansma, P., Prepetit, C., and de Cahbalier, J.B., 2008, Interseismic plate coupling and strain partitioning in the northeastern Caribbean: Geophysical Journal International, v. 174, p. 889-903, doi:10.1111/j.1365-246X.2008.03819x.

Petersen, M., Frankel, A., Harmsen, S., Mueller, C., Haller, K., Wheeler, R., Wesson, R., Zeng, Y., Boyd, O., Perkins, D., Luco, N., Field, E., Wills, C., and Rukstales, K., 2008, Documentation for the 2008 Update of the United States National Seismic Hazard Maps: U.S. Geological Survey Open-File Report 2008-1128, 61 pp.