While earthquakes happen all the time, some parts of the world are more susceptible than others - particularly in the Ring of Fire, a band of volcanoes and fault lines circling the edges of the Pacific Ocean.
Powerful earthquakes have recently hit Japan and Ecuador causing widespread damage and injuries
Japan was hit by two shallow quakes close to the city of Kumamoto over the past week, while a 7.8 magnitude quake struck Ecuador over the weekend.
Earthquake expert and chair of Geology at the University of Melbourne Professor Mike Sandiford spoke to SBS News about the quakes.
We saw Earthquakes of magnitudes exceeding 7.0 strike Japan and within hours also Ecuador is there any connection between the two?
The conventional wisdom is no. The earthquakes on either side of the Pacific are on different tectonic plates so far removed from each other that we don't have any physical mechanism that we would think would explain that they are connected. Having said over the last decade we have had a number of similar occurrences where large earthquakes have occurred very close in time, so I think the weekend's earthquakes will cause us to do a bit of rethinking. But my gut feeling is that these occurrences are coincidences.
What about the Ring of Fire which lies in the Pacific basin where both Ecuador and Japan lie. Can you explain what this is and how it relates to quakes we have seen recently?
The Pacific Basin is surrounded by tectonic plates which are moving towards each other. One of the plates comprising the oceanic crust subducts underneath the other plate and descends hundreds of kilometres into the earth's interior. The earthquakes occur along the plate interface and the volcanoes which create the Ring of Fire [occur] because of the subducted crust carrying water down deep inside the earth where it interacts with hot material and causes it to melt. Those melts rise to form the magma which is extruded from the volcanoes.
What about the recent earthquake in Tonga. Any connection with the others?
Again we would think that they're coincidences, because they are too distant from each other. We don't really have a mechanism to think about how the event in one place like Japan can be communicated tens of thousands of kilometres away in other locations.
You say there has been an increase in earthquake activity in the last few years. Why do you think that is?
We had a spate of very large earthquakes in the 1950s and 1960s of last century. Between about 1964 and 2004 we had no earthquakes greater than magnitude 8.3. Since the Boxing Day earthquake we've had a spate of very large earthquakes including the magnitude 9.2 to 9.3 Banda Aceh earthquake itself. There do appear to be changes in the amount of seismic energy released by the earth. Our seismological recording period only stretches back 100 years. It's still in its infancy given the natural time scales of earthquakes which repeat on timescales of thousands to tens of thousands of years.