Scientists doubt Haiti-Cayman earthquake link

Even though the magnitude-5.9 earthquake
felt in the Cayman Islands Tuesday occurred just a week after the magnitude-7.0
earthquake that devastated Haiti,
scientists do not believe the two events are related.

Dr. Lyndon Brown, research fellow
and head of the University of the West Indies Mona Earthquake Unit, said
Wednesday he didn’t believe the two earthquakes are related.

“We don’t think so because they
occurred on different faults,” he said. “We don’t see the unloading of stress
on one fault onto another fault, so we’re treating this as a separate event.”

However, Mr. Brown said it was
accepted that an earthquake that relieves stress from one end of a fault could
cause stress to accumulate on the other side of the same fault.  In the case of the earthquake in Haiti, which occurred along the
Enriquillo-Plantain Garden Fault, the other end of the fault is near Kingston, Jamaica.

Canadian geologist Murray Roed,
author of the book Islands from the Sea;
Geologic Stories of Cayman,
pointed out last week that not only was Grand
Cayman near a different fault – known as the Oriente Fracture Zone – but it was
not even on the same tectonic plate as Haiti and Jamaica.  The latter are part of the Caribbean plate
while the Cayman Islands are part of the North
American plate.

Mr. Roed said Wednesday that an
earthquake every year or so was common for Cayman.

“The Oriente fault is more or less
continually moving, but at a very slow rate,” he said. “It’s probably a good
thing that it’s continually moving at a slow rate.”

Last week, Mr. Roed said the fault
was moving about the same speed as fingernails grow. 

“The Caribbean
plate is quite active.  The activity
along the fault in Haiti
can be classed as very high.  The
activity near Cayman in comparison is low.”

Mr. Roed’s book points out the
there have been dozens of earthquakes near the Cayman
Islands between 1990 and 2004, and he didn’t think Tuesday’s
trembler was anything out of the ordinary.

“There’s no major reason for
concern, unless you get several of these in a row in a short period of time
like three or four weeks,” he said. “If that happened, then I think you should
be concerned that things are getting ready for a big move. 

“I frankly doubt that would happen.
The return for a major quake is very long in the Cayman area; something like
one in 700 years.”

Tuesday’s earthquake, which was
upgraded by the United States Geological Survey Wednesday from a 5.8-magnitude
to a 5.9-magnitude, was not even the strongest earthquake near Grand Cayman in recent times.   On 14 December 2004, a magnitude 6.8 quake
rattled nerves on the Island just three months
after Hurricane Ivan caused widespread damage. 
In February 2007, some residents felt a 6.2 magnitude earthquake that
occurred 75 miles northwest of Montego Bay, Jamaica, along the northern
boundary of the Caribbean plate.

In his book, Mr. Roed notes that
there is no historical record of any damaging earthquake events in the Cayman
Islands, but he noted minor effects on Grand Cayman from a quake in 1849 and
another one in East End in 1774.

Mr. Roed points out in his book
that sub-sea Cayman Ridge terrain and the Yucatan Basin
are considered to be part of the southern extremity of the North American
continent.

“This may be the reason that this
part of the Caribbean Sea floor appears to have been the most reasonably stable
portion of the Caribbean for perhaps 30 million years,” he wrote, adding
“…there appears to be a barrier that protects against large earthquakes
(greater than magnitude-7) that have affected other close-by areas.”

The same cannot be said for Jamaica, however, which is part of the more
volatile Caribbean plate.  Mr. Brown said another earthquake along the Enriquillo-Plantain Garden fault wasn’t a matter of if, but
when and where.

“We can only try to be as prepared
as we can,” he said.

Since last Tuesday’s disaster in Haiti, Mr. Brown said there has been a lot of
interest about earthquakes in Jamaica,
and not just from the scientific community.

“Everybody is interested,” he said.
“It makes everyone wonder if we’re going to be due one.”

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