Haiti likely to suffer more aftershock tremors
DOI: 10.1063/PT.5.024024
ISNS : The latest risk assessment for aftershocks from last week’s Haitian earthquake is in. Based on aftershock patterns of historical quakes, experts are forecasting a high chance of moderate tremors over the next 30 days, while measurements of the geological toll from the original earthquake reveal new regions at risk of another “big one” over the coming decades.
The US Geological Survey estimates a 90% chance that Haitians will feel a number of moderate temblors similar in size to Wednesday’s magnitude 5.9 aftershock over the next 30 days. Seismologists expect a series of two or three aftershocks of magnitude 5.0 or greater, which according to the USGS statement “will be widely felt and has the potential to cause additional damage, particularly to vulnerable, already damaged structures.
“The USGS experts have placed the odds of a strong magnitude 6.0 or greater aftershock, which would have 30 times the energy of a 5.0, at about one in four."Anyone living in Haiti or involved in relief work there must maintain situational awareness with regard to their personal earthquake safety,” warned the USGS. “Entry into or reoccupation of obviously damaged structures should be avoided.”
Aftershocks are common in the wake of a large earthquake. The initial magnitude 7.0 quake in Haiti was caused by the rupture and release of 200 years of strain that built up as the edges of two tectonic plates stayed glued together despite moving in opposite directions along the Enriquillo-Plantain Garden Fault. The aftershocks that people on Haiti will continue to feel are part of the geological repair process as the crack in the Earth readjusts itself. They are most likely to occur within the small region of the 300-mile-long fault that ruptured last week.
The chance of another large quake similar in size to the original earthquake has also increased in areas to the east and west of Port-au-Prince, outside of the 25 to 40 miles that ruptured last week. The strain in these areas of the Enriquillo fault, which have remained quiet thus far, has increased and is capable of producing another magnitude 7.0 quake, according to computer models that just finished crunching the data from last week’s quake.
Jian Lin, a USGS seismologist who studies the Caribbean, compares the situation to a city—the impact of the collapse of a large building may make other buildings more likely to fall.
“The problem is that for the largest earthquakes we really cannot forecast when they will happen,” said Lin. “We don’t know if it would happen in the next few months, next few years, or up to a hundred years from now.”
Devin Powell Inside Science News Service
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