1Great earthquakes do not happen just anywhere. They primarily occur in regions of the Circum-Pacific belt, known as “subduction” zones, such as Japan, Chile, Indonesia and Vanuatu. The latter zone was studied by seismologists from Orstom in the 1970s, when they were confronted with a trivial problem: in that part of the world, there are not enough land masses on which to install their measuring instruments.

Immersion of a seismometer, Ecuador.

2They teamed up with researchers from the University of Texas, in Austin, who developed self-contained ocean-bottom seismometers. This was a substantial technical achievement as these instruments can record very large amounts of data. However, this data could not be transmitted through the water column and had to be stored on site until it was collected by the researchers… which required very high-performance batteries. In addition, as these instruments were installed at the bottom of the sea, they had to withstand pressure and had to be brought back to the surface to deliver their information. In many aspects, ocean-bottom seismometers were more similar to robots than their land-based equivalents.

3After testing US prototypes, researchers began to develop their own instruments, the latest of which is currently being tested off the coast of Nice. It is equipped with lithium batteries and has a life span of at least three years. By comparison, previous generations, currently used in research, have a life span of six months. IRD owns 40 of those. Deployed in a network configuration, they shed light on the actual geometry of the Vanuatu subduction zone. In Ecuador, they were used to monitor the aftershocks of the great 2016 earthquake and enhance the understanding of the transfer of tectonic stress, notably towards the Colombian border where future earthquake rupture could potentially occur.