Source of devastating Morocco earthquake in 2023 discovered

A new study has revealed the likely source of the devastating earthquake that struck the High Atlas Mountains in western Morocco in September 2023.

The earthquake caused damage and destruction that claimed the lives of thousands in rural communities in the High Atlas Mountains region.

Prior to the 2023 event, the last major earthquake to affect Morocco occurred in 1960, and this long seismic silence of 63 years may have contributed to the region and its infrastructure being unprepared to deal with major tremors and the damage associated with them.

Most of Morocco’s seismic activity occurs near the Rif Mountains north of the 2023 quake’s epicenter, which are formed by the convergence of the African and Eurasian plates. But near the High Atlas Mountains, the highest in North Africa, with peaks rising more than 4,000 meters, the plates are converging at a rate of only about one millimeter per year.

According to the new study, published in the journal Geophysical Research Letters, scientists believe that rising seafloor waters beneath the High Atlas are the main reason these peaks have reached this height, rather than slow convergence.

By examining geodetic (the science of measuring and understanding the basic properties of the Earth's surface) and seismic data, an international team of scientists led by Kai Huang of the Southern University of Science and Technology in Shenzhen, China, and colleagues found that the 2023 Morocco earthquake originated in the Tizi N'Teste fault system at a fault level centered about 26 kilometers below the surface, and that the strongest rupture effects occurred at depths of 12–36 kilometers.

This event caused the displacement of the Moho, the boundary about 32 kilometers below the surface where the crust meets the mantle. 

Because the earthquake originated at such an unusual depth and occurred far from plate boundaries, scientists suggest the quake may have been caused by rising groundwater in the mantle, a process that helps lift the High Atlas Mountains, rather than by fault activity near the surface.

Rising bottom water in the mantle can inject fluids or magma along pre-existing faults, lowering the fault failure threshold and leading to seismic activity in the lower crust.

The results suggest that seismic hazard models should include more data on deeper dynamics in intraplate regions, which are often ignored in favor of plate boundary dynamics.

It also highlights the importance of seismic monitoring of areas, such as this one, where slow deformation rates and complex fault structures cause rare but devastating disasters.