First it was Japan, and then came Ecuador - two major earthquakes in the past days have killed dozens and rendered thousands of others injured and homeless. Were the two linked?
DW: On Saturday evening, anearthquake in Ecuador
was registered at 7.8 on the moment magnitude scale, immediately following a7.3 quake
on the other side of the Pacific, in Japan. Was there a connection between the two?
Günter Asch: Yes, and no. The reason these earthquakes happened in these places is that they both lie on the Ring of Fire, a region in the Pacific Ocean, and in both cases we are talking about tectonic subduction.
What happens during this kind of earthquake?
The Pacific Plate in the first quake and the Nazca Plate in the Ecuador quake are diving underneath the continental plates, and this means that great tension is being created where this happens. We call this seismic coupling, and when the tension has reached its threshold, the plates move and the ensuing rupture is what we call an earthquake.
What does subduction have to do with the Ring of Fire?
It's not only earthquakes that result when oceanic plates dive under continental plates. These forces are also essential for the formation of mountains, e.g. the Andes or even the Rocky Mountains.
And another effect is that the movement of the ocean floor leads to a mineral transmutation that eventually leads to the melting and solidification of magma, i.e., the formation of volcanoes. And these volcanoes impact directly how mountains are formed. In the end, the Andes, just as one example, are nothing other than tectonic subduction.
The Ring of Fire is like a kind of horseshoe around the Pacific Ocean. To what extent are the people living here in danger?
Within a span of 100 years, it is quite probable that an earthquake as strong as the ones registered in Japan and Ecuador will take place in their area. We are talking about a constant source of seismic tension that is created when plates behave this way.
This process takes place in a continuous manner. Of course, earthquakes happen at different intervals. But when a rupture happens, the zone where it took place is completely relieved of the tension that was amassing. There is a sense of quiet here, but this doesn't mean that the subduction stops. The tension begins building anew - until the next earthquake.
Could we perhaps have predicted that something was coming in Ecuador after the Japan earthquake?
No, not at all. With regard to the distribution of tension, these quakes have nothing to do with one another.
In other words - what happened in Japan didn't cause theearthquake
in Ecuador. Their simultaneity is, well, chance.
Günter Asch is a seismologist with the German Research Center for Geosciences in Potsdam. His work focuses primarily on tectonics in South America.