Has the Earth's Stress Been Released?
The following is a list of questions and answers compiled by the UWI Seismic Research Centre (Website: www.uwiseismic.com) following the Haiti Earthquake on January 12th, 2010. The Haiti Earthquake was of magnitude 7.0, caused major structural damage and resulted in thousands of deaths.
What type of plate movement caused this earthquake?
The northern boundary of the Caribbean plate exhibits left‐lateral strike‐slip motion and the fault plane solution of this earthquake is consistent with that regime. The Enriquillo‐Plaintain Garden fault system in southern Haiti appears to have hosted this earthquake. (Source: USGS).
Is it normal to have an earthquake of this size in the Caribbean?
Yes, it is normal to have an earthquake of this size and larger in the Caribbean. In the last three years at least three earthquakes greater than 7.0 magnitude have occurred in the Caribbean.
What is meant by a shallow earthquake?
Earthquakes that occur within the crust, which in the Caribbean is about 0‐35 km thick, are described as shallow earthquakes. Shallow earthquakes are generally felt more strongly than deep earthquakes since they are closer to the surface of the earth. The Haiti Earthquake was 13km deep which is a shallow earthquake.
What does this earthquake mean for neighbouring countries like Jamaica or Puerto Rico?
Countries in the near vicinity may have felt the earthquake. For example, the quake was reportedly felt along the Eastern corridor, particularly the North East and South East coasts of Jamaica. Assessments are being conducted to determine if there has been any structural damage to buildings and infrastructure. As strain adjusts in the area following the occurrence of an earthquake of this size, seismic activity in the area is expected to be somewhat elevated for some time to come.
If the earthquake occurred near Haiti how come it was felt in Caracas, Venezuela and not in any other islands in the Eastern Caribbean?
When an earthquake occurs, the energy is released in waves of different frequencies. The effect of the high frequency waves is reduced rapidly as they travel through the crust. The shaking generated by such waves mostly affects buildings with few stories. Therefore those closer to the earthquake in low‐rise buildings would be affected by these waves. Low frequency waves, on the other hand, can travel for greater distances and tall buildings respond to such waves. The report from Caracas came from someone on the 14th floor of a building. It may also be that features exist on the eastern side of the Caribbean plate that serve to lessen the energy of the waves coming from that direction reducing their effect as they pass through the region.
Are the Eastern Caribbean islands in any danger as a result of the Haiti Earthquake?
Large earthquakes can, in some cases, advance or delay the occurrence of some future earthquakes. That said the Eastern Caribbean is known to have a history of major earthquakes and the reality is that, with or without the occurrence of the Haiti earthquake, big damaging earthquakes can and will occur in the Eastern Caribbean.
Does the occurrence of this earthquake mean that stress has been released and so we probably won't have any big earthquakes in the region for a while?
No. In a zone that generates earthquakes, there is a system of faults of varying sizes. The distribution of faults in a seismically active area may be pictured as a pyramid with there being many small faults at the bottom of the pyramid and the number of faults scaling such that the bigger the fault the smaller the number. In the Haiti area there are fault segments that can generate earthquakes larger than magnitude 7.0 and these faults will continue to accumulate strain energy until they can absorb no more, at which time they will rupture. It is unknown, at this time, how close such faults are to their limit.
Where can I get more information on this earthquake?
The earthquake and subsequent aftershocks which occurred near Haiti on January 12th, 2010 are located in a region outside of the responsibility of the UWI Seismic Research Centre. The SRC monitors earthquakes, tsunamis and volcanoes for the English‐speaking Eastern Caribbean countries and as such it is inappropriate for the Centre to provide scientific advisories and updates on this event. Updates are available from the National Earthquake Information Center. http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/us2010rja6.php
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