Sat | Oct 1, 2016

Shaking Jamaica

Published:Friday | January 22, 2010 | 12:00 AM

Jamaica is riddled with earthquake fault lines, and we have about four earthquakes each week of the year, most of which are too slight to be felt. The website of the Earthquake Unit at the University of the West Indies, Mona (http://www.mona.uwi.edu/earthquake/jaequake.php) says: "About 200 earthquakes are located in and around Jamaica per year, most of which are minor, having magnitudes less than 4.0". As the tectonic plates push against each other, pressure builds up. Thank God for the 200 earthquakes per year; little quakes relieve stress; possibly it is these little quakes which have prevented us in recent times from getting a really big one.

The recent earthquake in Haiti was caused by motion along the Enriquillo-Plantain Garden fault zone (EPGFZ), which runs from Lake Enriquillo in the Dominican Republic, and extends across the southern portion of Haiti through the Caribbean Sea to the region of the Plantain Garden River in the parish of St Thomas, Jamaica.

The fault produces about 20.6 plus or minus 1.66 millimeters of lateral motion per year. Before the magnitude 7.0 earthquake near Leogane, Haiti on January 12, the largest event associated with the EPGFZ was the January 14, 1907 earthquake which destroyed Kingston.

There is as yet no science to forecast the occurrence of earthquakes, but history tells us that several other quakes have occurred in the region of the EPGFZ: Jamaica (Port Royal and Western Jamaica) in 1957, Jamaica (Kingston) in 1933, Jamaica (Kingston) in 1907, Haiti in 1860, Jamaica (Port Royal) in 1813, Jamaica in 1784, Jamaica (Savanna-la-Mar) in 1780, Haiti in 1770, Haiti in 1761, Hispaniola in 1751, Jamaica (Savanna-la-Mar) in 1744, Jamaica (Port Royal) in 1692, Haiti in 1684, Haiti in 1673, Haiti in 1618.What appears to be happening is that as the stress is relieved at one part of the Enriquillo-Plantain Garden fault zone, more stress is placed upon another part down the line; and so the epicentre shifts along the fault. During this time the epicentre appears to be moving westwards, towards Jamaica and the Cayman Islands.

Part of jamaica's history

Earthquakes have played an important part in shaping Jamaica's history. The 1692 earthquake which destroyed Port Royal led to the creation of a new city across the harbour, which came to be called Kingston. John Taylor, writing in 1688, said that in Port Royal there were 600 brick houses and 600 wooden houses, mostly four storeys high, with cellars, tiled roofs and sash windows. These tall brick houses, built English-style, would have been founded on sand, and were ripe for collapse once the sands started shaking. Port Royal was rebuilt after 1692, but not brick buildings four storeys high. That earthquake resulted in changes in building construction.

The 1907 earthquake was devastating to the city of Kingston, which was largely built of brick. Accounts of this catastrophe by Sir Frederick Treves and W. Ralph Hall Caine, both published in 1908, report solid brick walls bulging and collapsing, carriages being lifted and flung through the air, telegraph poles swaying like leaves in the wind, and great structures, whether made of iron, wood or stone, crumbling.

People were simply picked up and tossed, while struggling to maintain their balance. More often than not, they ended up resembling flailing pawns in an overturned chess game.

The authorities immediately prepared a new building code to govern building construction in Jamaica. It prescribes best practices to minimise earthquake damage. Would you believe that, more than 100 years later, that building code has not yet been made into law? At the moment, it still has the official status of being 'recommendations'. Why the long-standing reluctance in Jamaica to pass laws to constrain persons with means? Today, Jamaica's environmental laws fall into the same category.

Jamaica's location along the Enriquillo-Plantain Garden fault zone means that we are high-risk for earthquakes, and our building code must be legal and enforceable and of a pretty high standard. I consider this the greatest sort of dereliction of duty.

Some geologists, including Eric Calais of Purdue University and Paul Mann of the University of Texas, had warned as recently as 2008 that when the EPGFZ gave way, the result could be a quake of up to 7.2 magnitude. "Such studies should be considered high priority in Jamaica, Haiti and the Dominican Republic, given the seismic hazards posed by the fault," they wrote at the time.

The big one will come; it is just a question of when. Will our infrastructure be up to it?

Peter Espeut is an environmentalist. Feedback may be sent to columns@gleanerjm.com.