April - May 2008


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Shake, Rattle & Roll

What has history taught us about earthquakes?

“Many were killed. I lost five family members in the quake. But we have no time to weep. We have to work for the living right now.” Dawuti Aximu, a young Uighur man, told the Associated Press news agency in 2004, after an earthquake shook his village in the Chinese province of Xinjiang.

Almost 10,000 homes and 900 classrooms at 30 schools were levelled by the quake. At least 260 people died and more than 4,000 were injured. The quake had a severe effect on the local economy, which is heavily dependent on farming. One man who sells traditional rice and roasted mutton in the town said he had re-opened “because we all have nothing to eat. Everyone has to eat”.

“My house is gone. Three relatives are gone. But life goes on.”

Very few communities in the world have not been touched by natural disasters. In the Caribbean we’ve seen our share of tragedy. One catastrophic event that will forever be highlighted in our history books - the eruptions of Mt. Pelée in Martinique and St. Vincent’s Soufrière in 1902, where over 30,000 people died.

Today we have that fascinating, ominous fire breather in Montserrat, which has been erupting since 1995. The eruption of the Soufrière Hills volcano has made two-thirds of the island unsafe for human occupation, causing a mass migration of almost half of the population. The danger from an active volcano should not be taken lightly: ash can affect the operation of jet engines, and cause them to stall while breathing ash-laden air aggravates respiratory conditions, and prolonged exposure can cause damage to healthy lungs. Nature’s ingenious system of land reformation can be both beautiful and dangerous.

The Seismic Research Unit at The University of the West Indies has been actively monitoring earthquakes, volcanoes and tsunamis in the Eastern Caribbean and sharing this information with the general public since it was established in 1952. Experts have explained that , “In the global setting, the Caribbean is a relatively small plate. However, the processes involved in plate motion make the islands and countries lying on the plate boundary vulnerable to geological hazards sufficiently serious that they should be catered for in all long-term development plans.”

The earthquake and volcanic activity in the Eastern Caribbean result from the movement and sinking of the North American and South American Plates beneath the Caribbean Plate, a process described as subduction. On average, the Eastern Caribbean generates an earthquake of magnitude greater than 7.0 approximately every 20 years and one of magnitude 8.0 and above every one hundred years. The most recent strong earthquake was on 29th November, 2007 and occurred east of Martinique. However, there was no great earthquake, magnitude 8.0 and above, in the Eastern Caribbean during the 20th Century.

Throughout the region stakeholders including governments and architects, are becoming more aware of the need for urban planning with insight into natural disasters. History has taught us many lessons. Experts from the Seismic Research Unit explained that in the 19th Century when the colonial powers settled the islands of the Caribbean, and constructed buildings of stone, they did so ignorant of the earthquake hazard. Unfortunately the effects were disastrous- the great earthquake of 8th February 1843, east of the Lesser Antilles, between Guadeloupe and Antigua, was felt as far south as British Guiana. The high damage area had a radius of about 250 km, and extended from Saint Lucia to St. Martin. Close to the epicentral area, the city of Pointe-à-Pitre, in Guadeloupe, was destroyed and over 4,000 people lost their lives.

The Seismic Research Unit’s experts have explained that in the closing decades of the 20th Century, so-called natural disasters appear to have been on the increase. Research suggests that human activity has contributed in large measure to the phenomena of global warming with its associated consequences, the hole in the ozone layer, forest fires, flooding, to list just a few. Although the geological hazards do not appear to be susceptible to human activity in the same way, how and where we choose to live can and do affect the scale of the effects from earthquakes and their associated hazards. For example, for the death toll of 200,000, to be as high as it was for the 2004 Sumatran earthquake, and the associated tsunami, that number of people had to be in the affected areas at the time, absence of warning not withstanding. The SRU also suggests that “Choosing to introduce high-density population centres in coastal areas, going so far as to reclaim land to do so, in a region known to have significant seismic act ivity is imprudent, to say the least”.

A strong earthquake, magnitude 6.1 and over, occurs somewhere in the world, on average, every two to three days, and a great earthquake, magnitude 8 and above, approximately every year. But an earthquake does not have to be one of the biggest to produce catastrophic results. And so constant monitoring today, coupled with a greater understanding of the past, can only help us to better prepare for the future.

The Eastern Caribbean generates an earthquake of magnitude greater than 7.0 approximately every 20 years and one of magnitude 8.0 and above every one hundred years.

What is the Seismic Research Unit?
Based at The University of the West Indies’ St. Augustine campus, the SRU monitors earthquakes, volcanoes and tsunamis for the English-speaking islands of the Eastern Caribbean. When an earthquake occurs the Unit provides disaster management agencies with information on the size and location of the earthquake.

What is an earthquake?
Earthquakes are caused by the movement of plates (huge slabs of rock) making up the surface of the Earth. In volcanic islands, earthquakes may also be caused by the movement of magma beneath a volcano.

How are earthquakes measured?
Magnitude is the most common measure of an earthquake’s size and it is related to the amount of energy generated by the earthquake e.g. Magnitude 5.8. Intensity is a measure of the shaking and damage caused by the earthquake e.g. Intensity V.

The next time you feel an earthquake be sure to log on to our website at www.uwiseismic.com and tell us about your experience. This information helps scientists to determine the intensity of the earthquake.

Earthquake Effects
Some of the earthquake effects that can be harmful to people are:
  • Collapsing walls, buildings, and bridges.
  • Falling furniture, shattering glass windows and mirrors.
  • Falling electricity lines.
  • Broken gas lines.
  • Floods caused by the collapse of dam walls.
  • Rock slides or landslides.
  • Tsunamis - these are sea waves which can be generated by very large earthquakes.
  • Liquefaction - when solid ground behaves like a liquid and can no longer support buildings. This is common on reclaimed land.

Before an earthquake

  • Build your home in accordance with the recommended building codes. See your local disaster management office for details.
  • Bolt heavy furniture, water tanks, water heaters, gas cylinders and storage units to a wall or floor.
  • Place largest and heaviest items on lower shelves.
  • Emergency items such as canned foods, medication, flashlights, battery-operated radios, fire extinguishers and a First Aid kit should be readily available and working properly.
  • All family members should know how to use this emergency equipment and should know how to turn off electricity, gas and water using safety valves and main switches.
  • All family members should know what to do during an earthquake and should practice these safety tips through regular drills.

During an earthquake

  • STAY CALM. DO NOT PANIC. BE ALERT.
  • If inside stay inside, do not run out of the building.
  • If inside, stand in a strong doorway or get under a sturdy desk, table or bed and hold on.