The January 12, 2010, Mw 7.0 earthquake in Haiti: context and mechanism from an integrated geodetic study
On January 12, 2010, a Mw7.0 earthquake struck the Port-au-Prince region of Haiti, killing more than 200,000 people and causing an estimated \$8 billion in damages, $\sim$120\% of the country's GDP. Understanding this earthquake and its tectonic context is key to future hazard assessment and robust rebuilding in the region. The earthquake was originally thought to have ruptured the Enriquillo fault of the Southern Peninsula of Haiti, one of two main strike-slip faults accommodating the relative motion between the Caribbean and North American plates. Here we provide slip rates on major active faults from the first comprehensive Global Positioning System (GPS) velocity field for Hispaniola. These rates, together with the $\sim$250 years elapsed since a major event in southern Hispaniola, imply that the Southern Peninsula fault zone was indeed capable of a Mw7.1, consistent with previous estimates. We show that coseismic deformation from GPS and InSAR data is consistent with rupture on an unmapped north-dipping fault, which is subparallel to -- but different from -- the Enriquillo fault. The earthquake involved a combination of left-lateral strike-slip and reverse fault slip, consistent with the transpressional nature of regional interseismic strain accumulation. We will discuss the implications of these findings for the interpretation of the January 12 earthquake and future seismic hazard in the region.
The Role of Science and Engineering in Rebuilding a More Resilient Haiti (Invited)
Rebuilding a more disaster-resilient Haiti is the defining challenge in the wake of the devastating magnitude-7 earthquake that struck in January. The contrasting experience of Chile, which weathered a magnitude-8.8 earthquake in April with casualties in the hundreds, teaches us that building resilience is an achievable and desirable goal given suitable investments and governance. Scientists and engineers have much to contribute, but doing so requires effective mechanisms to enable them to inform the rebuilding process. The international donor community has been a key point of engagement since their funds provide the opportunity to build new schools, hospitals, critical infrastructure and housing that will not fail in the next disaster. In advance of a gathering of international donors at the end of March, the U.S. National Science and Technology Council’s interagency Subcommittee on Disaster Reduction convened a workshop that brought together over 100 scientists, engineers, planners, and policymakers, including a delegation of Haitian government officials and academics. Hosted by the University of Miami and organized by the Incorporated Research Institutions for Seismology, the workshop was co-sponsored by the U.S. Department of State, U.S. Agency for International Development (USAID), and United Nations International Strategy for Disaster Reduction with support from NASA, the National Science Foundation, and the U.S. Geological Survey (USGS). Key findings from the workshop covered the need to adopt and enforce international building codes, to use hazard assessments for earthquakes, inland flooding, and landslides in the planning process, and the central importance of long-term capacity building. As an example of one science agency’s contributions, the USGS informed the initial response by rapidly characterizing the earthquake and delivering estimates of population exposure to strong shaking that were used by humanitarian organizations, aid agencies, and the Haitians themselves. In the ensuing weeks, the USGS tracked aftershocks and issued statements with probabilities of future earthquakes. Early on, the U.S. Southern Command made it possible to put an advance team of engineers and a USGS seismologist on the ground in Haiti. That initial team was followed by the first major deployment of a USGS/USAID Earthquake Disaster Assistance Team, which evolved from the long-standing partnership between these two agencies. EDAT activities included field assessment of faulting, coastal uplift, and landslides; seismometer deployments for aftershock recording and characterization of ground shaking amplification; and development of a probabilistic seismic hazard map for Haiti and the whole island of Hispaniola. The team’s efforts benefited greatly from collaboration with Haitian colleagues with knowledge transfer occurring in both directions. The effort also benefited from significant remote sensing acquisitions, which helped to target field activities and constrain fault rupture patterns. Although the products have been put to use in Haiti, it still remains to turn hazard assessments into tools that can be used for effective planning, building code development and land-use decisions.
Networks in disasters: Multidisciplinary communication and coordination in response and recovery to the 2010 Haiti Earthquake (Invited)
The 12 January 2010 earthquake in Haiti demonstrates the necessity of understanding information communication between disciplines during disasters. Armed with data from a variety of sources, from geophysics to construction, water and sanitation to education, decision makers can initiate well-informed policies to reduce the risk from future hazards. At the core of this disaster was a natural hazard that occurred in an environmentally compromised country. The earthquake itself was not solely responsible for the magnitude of the disaster- poor construction practices precipitated by extreme poverty, a two centuries of post-colonial environmental degradation and a history of dysfunctional government shoulder much of the responsibility. Future policies must take into account the geophysical reality that future hazards are inevitable and may occur within the very near future, and how various institutions will respond to the stressors. As the global community comes together in reconstruction efforts, it is necessary for the various actors to take into account what vulnerabilities were exposed by the earthquake, most vividly seen during the initial response to the disaster. Responders are forced to prioritize resources designated for building collapse and infrastructure damage, delivery of critical services such as emergency medical care, and delivery of food and water to those in need. Past disasters have shown that communication lapses between the response and recovery phases results in many of the exposed vulnerabilities not being adequately addressed, and the recovery hence fails to bolster compromised systems. The response reflects the basic characteristics of a Complex Adaptive System, where new agents emerge and priorities within existing organizations shift to deal with new information. To better understand how information is shared between actors during this critical transition, we are documenting how information is communicated between critical sectors during the response and recovery phases. Our team consists of experts in natural hazards, public health, shelter and infrastructure, education, and security. We are performing a network analysis based on the content of news and situation reports in media and from UN and aid agencies, field reports by academics and organizations like EERI, and discussions with agencies in Haiti. During three trips to Haiti, we have documented what information was being collected by key stakeholders including government, United Nations, non-governmental organizations, and both domestic and international educational institutions. Insights gained from this analysis of disaster response and recovery operations are invaluable in informing the next state of risk reduction, the transition to a sustainable recovery in a damaged region.
The Role of Science and Engineering in Response and Reconstruction Following the 2010 Haiti Earthquake (Invited)
The 12 January 2010 Haiti earthquake (M7) provoked a strong interest in assistance, from people worldwide. Scientists and engineers offered their assistance in many forms, including the inspection of buildings and infrastructure to determine their safety for occupancy, and the monitoring of aftershock activity to better locate the causal fault and improve hazard analysis. Disaster specialists usually refer to four phases of emergency management: mitigation; preparedness; response; and recovery (or reconstruction). Mitigation and preparedness had been given low priority, given other challenges in the country, and the tasks associated with those phases must now be part of the recovery or reconstruction phase. At the same time as the humanitarian response effort was underway, the scientific and engineering communities developed plans for two general tasks: (1) assisting the community in their immediate needs; and (2) studying the effects and properties of the earthquake and its aftershocks. Some of the scientists and engineers had personal connections within Haiti, and organized their self-funded efforts through them; others followed a more formal route through funding agencies and international governmental protocol. The funded scientific studies and formal engineering analyses form the basis of this discussion. The engineering efforts spawned an independent review of damaged buildings, labeling them as appropriate either for occupancy, for occupancy after repairs, or for demolition. The scientific efforts led to a number of new observations and concerns over the actual causative fault and possible implications for future hazard. Both the scientific and engineering efforts are providing valuable information that is, and will continue to be, useful in improving our understanding of risk mitigation in Haiti and other places facing similar hazards. As the response phase gradually evolved into the recovery or reconstruction phase, the scientific and engineering communities united with the policy community in the USA to try to influence the reconstruction of Haiti using sound scientific and engineering practices. A workshop was held in late March in Miami on the subject of “Rebuilding for Resilience: How Science and Engineering Can Inform Haiti’s Reconstruction”. Details, including the key findings and presentations from the workshop, are available at http://www.iris.edu/hq/haiti_workshop/ . The scientific and engineering communities are becoming more aware of the relationship of their work to the needs of stricken or vulnerable communities, and many scientists and engineers have become personally and professionally involved improving the interaction with the humanitarian community. This work is not easy, and will fail unless individual scientists and engineers assume personal responsibility for continuing to promote good practices while assisting the capacity-building within recovering countries and those at risk.
The Enriquillo-Plantain Garden Fault in Haiti: Holocene Offsets and Seismic Hazard
The catastrophic M 7.0 Léogâne earthquake of 12 January 2010 in Haiti highlighted the hazard associated with the Caribbean-North American plate boundary in Hispaniola. Although the location of the epicenter and preliminary seismologic data suggested the earthquake was likely due to slip on the Enriquillo-Plantain Garden Fault zone (EPGFZ), more detailed analysis and modeling of data show that most, and possibly all, of the moment release occurred on a previously unidentified, blind thrust fault north of the EPGFZ (Hayes et al., in press; Calais et al., in press). This result implies that only a part of the accumulated plate-boundary strain was released by this earthquake, and that significant hazard still remains associated with the EPGFZ, the primary, plate-boundary strike-slip fault adjacent to Port-au-Prince in southern Haiti. Prior to the 2010 earthquake, this fault zone was known to be a significant plate-boundary fault, but no detailed Quaternary studies of the fault had been done. Geodetic models suggested that it accommodates 7±2 mm/yr of left-lateral slip, and historical accounts suggest it may be the source of at least three major historical earthquakes. Following the earthquake, we mapped Quaternary fault traces using satellite imagery, aerial photography, and LIDAR data. We also conducted a detailed ground-based assessment of the fault in the epicentral area and an aerial reconnaissance of the entire fault in Haiti. The geomorphic expression of the EPGFZ is especially prominent east of the 2010 epicenter where the Rivière Momance and Rivière Froide flow along strike valleys about 10 km south of Port-au-Prince (PAP). Here, the EPGFZ has an average strike of 085 degrees and a near-surface dip of 60-80 degrees south, which contrasts with the 50 degree north-dipping modeled fault for the 12 January earthquake. Along the EPGFZ, we found left-lateral stream offsets that range up to 160 m, indicating repeated left-lateral surface rupture in the Quaternary. We also found a set of nine small left-lateral offsets that range from 1.3-3.3 m along a 12-km-long section of the fault near Port-au-Prince, which are not visible on high-resolution imagery including LiDAR. We associate these small offsets with the most recent surface-rupturing earthquake, which is likely one of two historical earthquakes, in 1770 or 1751. The size range of the offsets implies that the earthquake was larger than M7.0. The lack of surface rupture in 2010 coupled with other seismologic, geologic, and geodetic observations suggest that the 2010 earthquake occurred on a previously unrecognized structure, now referred to as the Léogâne fault, and that the EPGFZ east of the 12 January epicenter remains a significant seismic hazard. Because the main EPGFZ closest to Port-au-Prince did not rupture in 2010, considerable strain remains to be released in an earthquake that poses a major hazard to densely populated parts of Haiti, including Port-au-Prince.
The 2010 Haiti earthquake sequence: new insight of the tectonic pattern from aftershocks and marine geophysical data : Haiti-OBS cruise
The devastating 2010 Haiti earthquake ruptured only a relatively short segment (~50km) of the Enriquillo-Plantain Garden fault (EPGF) a 600km long strike-slip fault running onland and offshore from Jamaica to Dominican Republic, with apparently no major surface rupture in the epicentral area. Considering the general behavior of such strike-slip fault (i.e. North Anatolian fault, San Andreas fault), we can expect that, following the 2010 earthquake, other large earthquakes will occur in the near future on adjacent segments. To contribute to the multinational scientific effort for a better understanding of the rupture process and the stress relaxation of this earthquake, we organized the Haiti-OBS cruise of the R/V L'Atalante few weeks after the catastrophe (Feb.5 to Feb.15, 2010, from and to Pointe-a-Pitre, Guadeloupe). Our goal was 1) to deploy a temporary network of seismologic stations -21 OBS, Ocean Bottom Seismometer, and 4 onland stations- and 2) to survey the detailed sea-floor features in relation with the deformation pattern of the area (multibeam bathymetry and mud-penetrator). We show that the distribution pattern of the aftershocks as well as the compressive surface structures observed in the geology and onshore/offshore morphology of the area are consistent with a deformation model implying a major left-lateral component along the EPGF, and a strong reverse component. The January 12, 2010 mainshock has been shown as very complex. However, in the first order, the mainshock and the distribution of the aftershocks, better localized by our temporary network, can be explained by the interaction between the strike-slip EPGF system and a blind folds-and-thrusts system. Thus, the general geological setting shows a southern extension until the southern part of the Canal du Sud area of the well-known fold and thrust system of the Hispaniola main block.
Seismic Monitoring and Post-Seismic Investigations following the 12 January 2010 Mw 7.0 Haiti Earthquake (Invited)
We report on ongoing efforts to establish seismic monitoring in Haiti. Following the devastating M7.0 Haiti earthquake of 12 January 2010, the Bureau des Mines et de l’Energie worked with the U.S. Geological Survey and other scientific institutions to investigate the earthquake and to better assess hazard from future earthquakes. We deployed several types of portable instruments to record aftershocks: strong-motion instruments within Port-au-Prince to investigate the variability of shaking due to local geological conditions, and a combination of weak-motion, strong-motion, and broadband instruments around the Enriquillo-Plaintain Garden fault (EPGF), primarily to improve aftershock locations and to lower the magnitude threshold of aftershock recording. A total of twenty instruments were deployed, including eight RefTek instruments and nine strong-motion (K2) accelerometers deployed in Port-au-Prince in collaboration with the USGS, and three additional broadband stations deployed in the epicentral region in collaboration with the University of Nice. Five K2s have remained in operation in Port-au-Prince since late June; in late June two instruments were installed in Cap-Haitien and Port de Paix in northern Haiti to provide monitoring of the Septentrional fault. A permanent strong-motion (NetQuakes) instrument was deployed in late June at the US Embassy. Five additional NetQuakes instruments will be deployed by the BME in late 2010/early 2011. Addionally, the BME has collaborated with other scientific institutions, including Columbia University, the Institut Géophysique du Globe, University of Nice, the University of Texas at Austin, and Purdue University, to conduct other types of investigations. These studies include, for example, sampling of uplifted corals to establish a chronology of prior events in the region of the Enriquillo-Plantain Garden fault, surveys of geotechnical properties to develop microzonation maps of metropolitan Port-au-Prince, surveys of damage to public buildings, and a continuation of GPS surveys to measure co- and post-seismic displacements in collaboration with researchers from Purdue University. Preliminary analysis of aftershock recordings and damage surveys reveals that local site effects contributed significantly to the damage in some neighborhoods of Port-au-Prince. However, in general, bad construction practices and high population density were the primary causes of the extent of the damage and the high number of fatalities.
Triggering of the 2010 Haiti earthquake by hurricanes and possibly deforestation
The January 12th, 2010, M = 7.0 Haiti earthquake was one of the worst natural disasters of the past century. This devastating earthquake caused the death of more than 200,000 people, the injury of about 300,000 people, and left about two million people homeless. Just a year and a half prior to the earthquake, Haiti was subjected to another severe disaster, flooding induced by two hurricanes and two tropical storms (Fay, Gustav, Hanna and Ike). Both natural disasters results in death and destruction, but because their origins are very different, they are generally considered to be unrelated phenomena. We suggest a physical link between these two destructive events, in which the 2010 Haiti earthquake was triggered by rapid erosion induced by hurricane activity. The suggested denudation triggering mechanism is consistent with seismic and geodetic analysis on the earthquake rupture, indicating an initial oblique motion on a southward dipping fault followed by intense reverse faulting on a northward dipping fault (Hayes et al., 2010). Our triggering analysis is based on interdisciplinary research using satellite imagery, bathymetric charts, detailed DEM, and 3-D mesh-free finite element modeling. Remote sensing analysis of the nearby Leogane Delta’s growth over the past 35 years indicates a rapid delta build up due to a mean erosion rate of 6 mm/yr. Theoretical calculations based on finite element modeling and Coulomb failure stress criterion suggest that denudation-induced stress changes at the hypocenter reached the earthquake’s triggering threshold (3 kPa) after 60-80 years at the present day erosion rate. Our results also suggest that the rapid sediment deposition in the delta kept clamping the northward dipping fault allowing a continuous stress build up on the fault, which explains the large amount of seismic energy released by this fault during the earthquake. Haiti’s massive deforestation most likely contributed to the rapid erosion in the past several decades and the heavy tropical rains contribute to efficient sediment transport. The heavy rain poured during the 2008 hurricane season flushed the drainage system in the epicenter area and removed the last significant sediment load that triggered the 2010 Haiti earthquake.