No abstract

A seismic site classification microzonation for the city of Port-au-Prince is presented herein. The microzonation is based on 35 shear wave velocity ( VS) profiles collected throughout the city and a new geologic map of the region. The VS profiles were obtained using the multichannel analysis of surface waves (MASW) method, while the geologic map was developed from a combination of field mapping and geomorphic interpretation of a digital elevation model (DEM). Relationships between mean shear wave velocity over the upper 30 m of the subsurface ( VS30) and surficial geologic unit have been developed, permitting code-based seismic site classification throughout the city. A site classification map for the National Earthquake Hazards Reduction Program/International Building Code (NEHRP/IBC) classification scheme is provided herein. Much of the city is founded on deposits that classify as either NEHRP Site Class C or D, based on VS30. Areas of the city requiring additional subsurface information for accurate site classification are noted.

Presented herein are the results of geotechnical investigations and subsequent laboratory and data analyses of the Port-au-Prince seaport following the Mw7.0 2010 Haiti earthquake. The earthquake caused catastrophic ground failures in calcareous-sand artificial fills at the seaport, including liquefaction, lateral spreads, differential settlements, and collapse of the pile-supported wharf and pier. The site characterization entailed geotechnical borings, hand-auger borings, standard penetration tests, and dynamic cone penetration tests. The laboratory tests included grain size and carbonate content tests. The observations and results presented herein add valuable field performance data for calcareous sands, which are relatively lacking in liquefaction case history databases, and the overall response of the artificial fills are consistent with predictions made using semi-empirical relations developed primarily from field data of silica sands.

The 2010 Haiti earthquake represents one of the most devastating earthquakes in history. Damage to structures was widespread across the city of Port-au-Prince, but its intensity varied considerably from neighborhood to neighborhood. This paper integrates damage statistics with geologic data, shear wave velocity measurements, and topographic information to investigate the influence of these conditions on the damage patterns in the city. The results indicate that the most heavily damaged areas in downtown Port-au-Prince are underlain by Holocene alluvium with shear wave velocities that average about 350 m/s over the top 30 m. The remainder of Port-au-Prince is underlain mostly by older geologic units with higher shear wave velocities. Damage was also concentrated on hillsides around Port-au-Prince. These pockets of damage appear to have been caused by a combination of factors, including topographic amplification, soil amplification, and failure of weakly cemented, steep hillsides.

The 12 January 2010 Haiti earthquake (Mw 7.0) caused extensive damage to the Port-au-Prince region, including severe liquefaction failures along the Gulf of Gonâve coastline, along rivers north of Port-au-Prince draining into the Gulf, and a liquefaction-induced structural/bearing capacity failure of a three-story concrete hotel along the southern coast of the Gulf. During two reconnaissance missions, the authors documented ground conditions and performance at eight sites that liquefied and two sites that did not liquefy. Geotechnical characterization included surface mapping, dynamic cone penetration tests, hand auger borings, and laboratory index tests. The authors estimated median peak ground accelerations (PGAs) of approximately 0.17g to 0.48g at these sites using the Next Generation Attenuation (NGA) relations summarized by Power et. al. (2008) . These case histories are documented here so that they can be used to augment databases of level-ground/near level-ground liquefaction, lateral spreading, liquefaction flow failure, and liquefaction-induced bearing capacity failure.