For the first time, scientists have observed live the movement of a slow earthquake to the bottom of the ocean. These events, imperceptible on a human scale, could play a key role in the prevention of tremors of terre destructive.
This major discovery was made along the Nankai fault, off Japan, an area known for its violent earthquakes. The researchers used ultra -sensitive sensors to follow these slow tectonic movements, which are spread over several weeks.
– Magnitude earthquakes ≥ 7.0 (depth 0–69 km).
– Active volcanoes.
Image USGS
How do slow earthquakes work?
Slow earthquakes gradually release the energy accumulated between two tectonic plates. Unlike conventional earthquakes, they do not cause brutal jerks but reduce tensions in depth. These events propagate at a speed of one to two kilometers per jour. The sensors have detected tiny movements, just a few millimeters along the flaw.
Scientists have also found that these earthquakes occur in areas where the pressure of underground fluids is abnormally high. This observation confirms the influence of fluids in the triggering of slow shifts.
A step forward for the seismic forecast
The Nankai flaw generated in 1946 an earthquake of magnitude 8, killing more than 1,300 people. The new data suggests that slow earthquakes could alleviate the risk by dissipating part of the accumulated energy.
This discovery could improve tsunamis forecasting models. By better understanding these mechanisms, the researchers hope to identify other areas at risk, such as the Cascadia flaw, near the American coast.
The sensors used, of unprecedented precision, open the way to finer monitoring of underwater flaws. These tools could improve our understanding of silent tectonic movements.
