What is an earthquake?
Earthquakes are caused by the movement of plates (huge slabs of rock) making up the surface of the Earth. The region where two or more plates meet is called a plate boundary. The plates are constantly moving but this plate movement is neither smooth nor continuous, rather the plates often lock together at plate boundaries causing a build-up of energy. When the plates eventually move out of this locked position the energy that is released may be felt as an earthquake.
Where do most earthquakes occur?
Much of the world’s earthquake and volcanic activity takes place along plate boundaries, the area where plates meet. Countries located along plate boundaries, such as the Eastern Caribbean islands, Japan, Chile and the USA (California) are likely to experience earthquakes. At these plate boundaries the plates interact with each other in different ways; some of them slide past each other, others spread apart and others move toward each other with crumpling or with one dipping beneath the other. This last type of plate boundary is called a subduction zone which is the main type of plate interaction occurring in the Eastern Caribbean.
What is a fault?
A fault is a plane along which rocks are displaced. Faults can vary in size from the smallest that can be recognized at about 2 cm to large plate boundaries hundreds of kilometers long.
What is meant by an ‘earthquake sequence’?
A significant magnitude earthquake with which is associated, in time and space, smaller magnitude earthquakes (the lower the magnitudes, the higher the numbers of events), possibly preceding, but certainly following, is described as an earthquake sequence.
Why is it that earthquakes in some parts of the world like India, China, or Turkey seem to be more devastating than earthquakes in the Caribbean?
The rate at which faults accumulate strain energy and release it in earthquakes is directly proportional to how fast plates move. The convergence rate of the plates in the Eastern Caribbean is about 2 cm/year, while the rate in Asia is much higher. As a result, their largest earthquakes occur more often than those in the Eastern Caribbean. This means that one day an earthquake as large as those seen in Asia will occur in the Eastern Caribbean.
What is the difference between volcanic earthquakes and tectonic earthquakes?
As magma makes its way through the crust to the surface of the earth, it breaks apart surrounding rock thereby generating volcanic earthquakes. Volcanic earthquakes are one of the main signs that a volcano is restless.
Tectonic earthquakes are caused by the movement of plates when energy accumulated within plate boundary zones is released. Tectonic earthquakes are usually larger than volcanic earthquakes.
What is a foreshock/aftershock?
The terms foreshock and aftershock have no strict scientific definition. They are used to describe the events within an earthquake sequence to distinguish those events that preceded the mainshock from those that followed it.
Can an aftershock have a larger magnitude than the main earthquake?
The term mainshock refers to the largest event in a sequence. However, as energy release within a seismogenic system proceeds, it may be found that an event that was thought to be the largest was not the mainshock and a larger event occurs. The category into which events within a sequence would fall can only be definitely set after the high level activity of the sequence is complete. Research is ongoing to try to distinguish between large magnitude precursory events and mainshocks as the events are occurring (i.e. in real time).
Can climate change or hot weather cause earthquakes?
No, climate change or hot weather does not cause earthquakes. Earthquakes are caused by processes deep within the Earth while hot weather and climate change are related to the atmosphere
Can earthquakes be predicted?
Scientists are unable to predict the location, time and date of when an earthquake will occur, however, forecasts can be made based on past patterns of activity in a region. The Eastern Caribbean is a seismically active area, which has generated very large earthquakes in the past. Therefore, we will continue to have earthquakes of varying magnitudes.
Are there earthquakes on planets other than Earth?
The easy answer is “no”. They would not be called “earthquakes” if they don’t occur on Earth. The real answer is that we would expect earthquakes to occur on any rocky planet which has Plate Tectonics. In our Solar System, only the Earth has active Plate Tectonics. But other solar systems will have formed in the same way as ours and it would be very surprising if there were no planets with Plate Tectonics.
We detect earthquakes on Earth using sensitive instruments called seismometers. Four of the Apollo missions to the Moon deployed seismometers. You can find a photo and some more information on NASA’s web site. There is no evidence of Plate Tectonics on the Moon and so scientists were a bit surprised at the number of Moonquakes they recorded. Most of these are generated by the strong gravitational force of the Earth. NASA are now planning to return to the moon and might have to plan for moonquakes.
One of the early unmanned missions to Mars (Viking 2) included a seismometer. In the short time it was operating, it recorded no conclusive evidence of Marsquakes. None of the recent Mars missions included seismometers.
Amazingly, there is some evidence for earthquakes on the Sun, or Sunquakes. These Sunquakes are very different from Earthquakes and Moonquakes and maybe should be called something else.
Can an earthquake trigger a volcanic eruption?
Yes. Research suggests that large earthquakes can both trigger a volcano to begin erupting or shut down a volcano that is already erupting.
Does drilling for oil cause earthquakes?
In some parts of the World, earthquakes have been found to be associated with oil exploration.