The earth surface is made up of many huge pieces of rock, like a jigsaw puzzle, call tectonic plates. An Earthquake is a sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the earth's crust or volcanic action
For hundreds of millions of years, the forces of plate tectonics have shaped the earth, as the huge plates that form the earth's surface slowly move over, under and past each other. Sometimes, the movement is gradual. At other times, the plates are locked together, unable to release accumulated energy. When the accumulated energy grows strong enough, the plates break free. If the earthquake occurs in a populated area, it may cause many deaths and injuries and extensive property damage
Types of tectonic plate activity
Earthquake activity in St. Vincent and the Grenadines is a result of various types of movements taking place within boundary zones of the Caribbean Plate.
There are generally three kinds of plate movements which can cause an earthquake:
Spreading: when plates are spreading or separating from each other, we call the movement divergent
Colliding: when plates are colliding, or pushing each other, we call the movement convergent
Sliding: when plates are sliding past each other we call this movement lateral
Magnitude is related to the energy generated when a fault ruptures and produces an earthquake. There are different ways to determine magnitude. In one method, three characteristics of the fault zone are used in the calculation:
- The area that ruptures during the earthquake.
- The amount of displacement during the earthquake.
- The stifness of the rocks that break.
When we multiply these numbers, we obtain a number called the seismic moment. The seismic moment is then converted into another number called the moment magnitude (or simply magnitude). In our region, we use the duration of the earthquake recording, and the distance of the recording station from the hypocentre to find magnitude e.g. magnitude 5.8.Â For any given earthquake, the magnitude is a fixed number that does not vary regardless of which island you are located.
Intensity scales describe the severity of an earthquake by grading the effects on people, structures and geological formations. Each degree of intensity is described by a Roman numeral, (I, II, III etc.) and the effects of the earthquake roughly double in severity for each one-division increase in intensity. In the Western hemisphere, including the Eastern Caribbean, the most widely used scale is called the Modified Mercalli or MM scale. In the rest of the world an almost identical scale called the MSK scale is more common.Â
For any given earthquake, the Intensity may vary depending where you are in relation to the earthquake's epicenter.
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Earthquakes cannot be predicted so it is important to prepare yourself as soon as possible:
If you are inside when the shaking starts you should:
If you are outside when shaking starts you should:
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To learn more about earthquakes that have affected St. Vincent and the Grenadines please click below: