Haitian Earthquake

Marco Allain
ES 767 Global Tectonics, Emporia State University
Spring 2012

Magnitude
Geology
Predictions
Recovery
Conclusions
References


Magnitude

On January 12, 2010, the island of Hispaniola experienced a large earthquake. Hispaniola is divided into two countries, Haiti to the west and the Dominican Republic to the east. The epicenter of the earthquake was only 25 km west of Port-Au-Prince and 130 km east of Les Cayes, Haiti. The depth of the earthquake was 13 km, implying that it was a shallow event. This is significant because, as senior research scientist at the University of Texas Paul Mann explains, the vast majority of severe earthquakes are shallow rather than deep events (Romero 2010). The earthquake had a magnitude of 7.0 on the Richter magnitude scale with any earthquake of 7.0 or higher being listed as “Major.” Port-Au-Prince is the Haitian capital and it was merely 15 miles away from the epicenter. This caused significant shaking and destruction to the most densely populated area in Haiti.

View of all major cities in the region. Clearly the largest cities are all located on the island of Hispaniola. USGS, 2012.

Zoomed in view of all major cities and the imapact felt there The most severe effects were felt in the capitol, leading to high civilian casualties. USGS, 2012.
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Geology

Rodriguez (2007) states that Hispaniola sits on the Enriquillo fault, the boundary between the Caribbean and North American tectonic plates. The Enriquillo is a slip-strike fault, where two portions of the Earth's crust are sliding past each other. Geologists believed that the plate boundary was located in the northern part of the island, but significant fault activity was discovered in the south as well. The geologic community was aware that there was a potential problem but little was done by Haiti to prepare for seismic events. The Caribbean plate is moving east and the two parts of the island are moving apart at a fairly quick rate by geologic standards. The fault is shallow so it is near the surface causing severe shaking and rolling surface waves.

Given a one centimeter a year movement for centuries, the 7.0 quake represented a tremendous release of energy. This is not unprecedented. There are records of big earthquakes on the southern coast going back to the mid-1600s. The last substantial earthquake in the area, an 8.0 temblor, was in 1946 in the Dominican Republic. Most people in Haiti don't remember that earthquake. There is a political boundary and a language barrier between Haiti and the Dominican Republic, so few lessons were learned from the 1946 earthquake. Therefore the Haitian infrastructure and city planning was inadequate to withstand the 7.0 magnitude earthquake the island experienced in 2010.

Map of seismic shaking by the USGS

Earthquakes at strike-slip faults are common. For instance, the San Andreas Fault is a strike-slip fault formed where two plates of the earth’s crust slide past each other.

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Predictions

Geologists estimate earthquake probabilities in two ways: by studying the history of large earthquakes in a specific area and the rate at which stress accumulates in the rock. Geologists study the past frequency of large earthquakes in order to determine the future likelihood of similar large shocks with a certain level of statistical probability. Another way to estimate the likelihood of future earthquakes is to study how fast stress accumulates. When plate movements build the stress in rocks to a critical level the rocks will suddenly break and slip to a new position. Geologists measure how much stress accumulates along a fault segment each year, how much time has passed since the last earthquake along the segment, and how much stress was released in the last earthquake. Both of these methods, and a wide array of monitoring techniques, are being tested along the strike-slip boundary of the Enriquillo fault.

Graph of Fatality risk issued before the earthquake. Graph provided by the PAGER system.

The PAGER system provides an early summary of the basic parameters, including origin time, local time and magnitude every 30 minutes about possible earthquakes and is dispensed by the USGS. These warnings were issued before the Haitian earthquake. These figures display the Red Alert system. The Red Alert system assesses shaking-related fatalities and economic losses. When the graph has a high percentage in the red areas, high casualties and extensive damage are probable and the disaster is likely widespread. Past red alerts have required a national or international response. Estimated economic losses prior to the earthquake were 20-100% GDP of Haiti.

Graph of Economic damage potential issued before the earthquake. Graph provided by the PAGER system.

As of today, scientists are not able to predict earthquakes. Thousands of earthquakes occur each day, although most are too small to be detected. The problem is in pinpointing the area where a strong shock will occur. Aftershocks and even some large tsunamis related to earthquakes can be predicted but only with great difficulty and little certainty. The need to make seismologic advancements is obvious. Even recently the region reminded the world that Haiti’s strike-slip fault is indeed active. On March 25, 2012 there was a magnitude 3.6 intensity earthquake 28 km from Port-Au-Prince. Earthquake prediction may one day become a reality, but only after much more is learned about the earthquake mechanism and the convective core below.
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Recovery

Below is a graph depicting the 1 in 15 death ratio of Haitians affected by the earthquake. This rate is compared to recent death-to-life ratios of earthquakes magnitude 6.0 or higher in China and Italy. Rodgers (2010) accentuated the differences between these three earthquakes. The disparity is attributed to city planning and poor disaster response by the Haitian government and international community.

before

Rescue efforts are a large portion of disaster response. Keeper (2011) explains that Haiti is an impoverished country with inadequate search and rescue systems. This fact is accentuated when Haiti’s rescue efforts are compared to those of Italy and China. This disparity helps explain the 1 in 15 death rate displayed in the previous figure.

before

Governments can significantly reduce earthquake mortality by enforcing quake-proof construction regulation. Many countries still do not prioritize such construction projects. Mortality is lower in countries with higher earthquake propensity and mortality is higher in countries like Haiti with low earthquake propensity. Bilham (2010) stated that the devastation in Haiti is due in part to the weak infrastructure. Haiti is a poor country with many poorly built houses and buildings. Most structures in Port-Au-Prince were destroyed during the earthquake. Civilians trapped in such structures were generally killed. Haiti is now learning from this and sturdier earthquake resisting structures are replacing those that were lost.

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Conclusions

In the 2010 earthquake 316,000 people were killed. Yates (2011) reports that 1.5 million Haitians were left homeless. 32 aftershocks of magnitude 4.2 or greater were recorded merely nine hours after the initial shaking. Only 50% of all debris has been removed two years after the earthquake. This is by far the most destructive earthquake of this century. So clearly, scientific understanding of the Haitian earthquake is of vital importance. As the population increases, expanding urban development and construction works encroach upon areas susceptible to earthquakes like fault boundaries or geologic hot spots. Haiti was ill-prepared for the earthquake it experienced in 2010. Restoration efforts intend to improve building guidelines and disaster preparedness to prevent such destruction from any future earthquakes. With a greater understanding of the causes and effects of Caribbean earthquakes, we may be able to reduce damage and loss of life from future seismic events.

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References

Website created by Marco Allain on March 28, 2010

ESU Earth Science Department homepage

For more information on the Haitian earthquake, visit the USGS
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