This Rapid Response Research (RAPID)award provides funding to allow the investigators to augment previous, limited-scope DCPT and Vs investigations with additional and deeper investigations into the effects of the Haiti earthquake.
The magnitude 7.0 earthquake that struck Haiti on January 12, 2010 caused tremendous damage to the built and natural environment, destroying buildings, crippling the Port-au-Prince seaport, and causing large coastal, roadway, and slope failures. The PIs participated in a reconnaissance trip to Haiti as part of a Geo-engineering Extreme Event Reconnaissance team. The team published preliminary findings at: www.geerassociation.org/GEER_Post%20EQ%20Reports/Haiti_2010/Cover_Haiti10.html. The team brought back an extensive set of data from this initial reconnaissance, including shear wave velocity (Vs) and dynamic cone penetration test (DCPT) data at several sites.
However, after an initial damage assessment and an evaluation of preliminary findings, a number of critical details that require further investigation have been identified. Given the tremendous damage that resulted from this earthquake, it is imperative that the profession maximize what is learned from this event in order to minimize damage during future earthquakes in Haiti, in other developing coastal nations, and elsewhere around the world.
The intellectual merit of this activity is threefold. (1) The team will augment previous, limited-scope DCPT and Vs investigations with additional and deeper investigations, as well as soil sampling and lab testing to understand liquefaction in carbonate sands, as these sands are poorly represented in the worldwide liquefaction case history database despite their worldwide presence. This work will chiefly involve sampling and testing along the southern coast of Port au Prince Bay, primarily between Leogane and Petit Goave, and along the major rivers north of Port au Prince. Subsequent lab testing will include ring shear and cyclic triaxial testing. (2) The team will expand initial observations of potential topographic effects on damage patterns on the hillsides and slopes in communities surrounding Port-au-Prince, such as Petion-Ville. This effort will involve collecting slope strike and dip angles, proximity to ridge tops, and obtaining shallow Vs measurements in areas identified with noticeable damage patterns apparently influenced by topography. (3) The team will collect 15 to 20 near-surface Vs profiles in low-lying areas of Port-au-Prince where potential soft-soil amplification effects leading to noticeable damage patterns are observed. These measurements will be spatially-distributed in both areas that suffered heavy damage and areas that suffered minimal damage. These efforts will be enhanced using innovative 3D imaging software and calibrated digital cameras to develop 3D digital elevation models of damage at these sites.
The broader impacts of this project are focused on training students and improving the state-of-practice of engineering. Each team member will bring one graduate student to train them to perform reconnaissance and will encourage them deliver seminars about their experiences and the team will interact with personnel from Ministry of Mines and Natural Resources in Haiti. Additionally, the team will publish findings on liquefaction of carbonate sands, topographic effects, and site effects. Evaluating geophysical data and laboratory testing of samples recovered at select sites will also involve training graduate and undergraduate students.
This award is co-funded by the NSF Office of International Science and Engineering (OISE).
The magnitude 7.0 earthquake that struck Haiti on January 12, 2010 caused tremendous damage to the built and natural environment, destroying buildings, crippling the Port-au-Prince seaport, and causing large coastal, roadway, and slope failures. Our team brought back possibly the most extensive set of "hard" data ever collected on an initial reconnaissance, including shear wave velocity (Vs) and dynamic cone penetration test (DCPT) data at several sites. However, after seeing the damage first-hand and evaluating our preliminary findings, we have identified a number of key items that require further investigation to understand. Given the tremendous damage that resulted from this earthquake, it is imperative that the profession learn all that we can from this event in order to minimize damage during future earthquakes in Haiti, in other developing coastal nations, and elsewhere around the world. During a week-long reconnaissance to the Port-au-Prince region in April 2010, the project team performed coordinated geologic mapping; conducted borings, soil sampling, and DCPT investigations; and collected 36 deep Vs profiles. Using the geologic mapping, Vs profiles, and a Digital Elevation Map (DEM) produced by others, the project team developed a new near-surface geology map for greater Port-au-Prince (Image 1). This map was used as the basis for correlating geology, topography, subsurface Vs profiles, and damage patterns. Building damage states from UNOSAT and GEO-CAN inventories were reviewed and compared with field damage assessments performed by the project team for over 400 buildings. The UNOSAT inventory was over 75% accurate and assigned damage states to all buildings; therefore it was used by the project team. As illustrated in Image 2, the most severe damage (i.e., highest Damage Intensity) was observed in the Holocene alluvium (Qham), which underlies much of downtown Port-au-Prince. Softer soil conditions are found in the artificial fill (Af) unit, but the Damage Intensity within this unit was smaller due to the presence of predominantly shantytown construction with corrugated metal roofs. Damage was also less intense within older Pleistocene fan (Qpf) deposits due to its larger stiffness. Damage Intensities in the older Pliocene fan (Pf) and Mio-Pliocene fangolmerate (Mpb) often were significant due to combined topographic effects and soil amplification. Within these units, damage often was concentrated either at ridge tops or along steep valley slopes (Image 3). The project team used the Vs profiles to develop a seismic site classification microzonation map for greater Port-au-Prince (Image 4). These maps are used by regional planners and engineers to assess potential amplification of ground shaking during an earthquake, with higher amplification commonly occurring in softer soil deposits (indicated as higher site class letters, e.g., Site Class D). As illustrated in Image 4, the softer site classifications are generally confined to Holocene alluvial deposits and coastal artificial fills. Extensive liquefaction (i.e., loss of soil strength during earthquake shaking) and lateral spreading (i.e., shallow, rapid landslides that occur in liquefied soils during earthquakes) occurred in artificial fills in Port-au-Prince and in Holocene alluvial deposits and floodplain soils as the rivers approached the Gulf of Gonave. Images 5 and 6 illustrate a dramatic coastal lateral spread and liquefaction-induced bearing capacity failure of a three-story hotel building along the Gulf of Gonave coast near L’Acul. Documenting these lateral spreads, liquefaction-induced flow failures, and liquefaction-induced bearing capacity failures are crucial to better predicting (and thus preventing) similar failures during future earthquakes. The project team included four U.S. graduate students who learned how to perform geotechnical field reconnaissance following an earthquake. Since April 2010, all of the project team members have delivered numerous seminars describing our experiences. To name just a few, these seminars have been delivered to American Society of Civil Engineers, the Corps' of Engineers, National Society of Professional Engineers, the Geological Society of America, the Seismological Society of America, the Girl Scouts of America, and numerous public and private elementary schools and other public forums. These activities have greatly increased the public's knowledge of earthquakes, earthquake engineering, and the plight of Haitians following the devastating January 2010 earthquake. Lastly, the project team is remaining involved in the rebuilding and training efforts in Haiti by continuing to interact with Haitian officials involved in reconstruction. In particular, the geology and seismic site class microzonation maps developed by the project team have proven to be quite valuable to the reconstruction effort.
