Spain’s deep earthquakes linked to Mediterranean’s upside-down crust: study

A recent study has revealed that Spain is at risk of experiencing uncommon and profound earthquakes due to a tectonic plate that has flipped upside down beneath the Earth’s crust. This geological phenomenon occurred as the African and Eurasian plates slowly converged, causing a section of the Earth’s surface to invert and plunge deep below the Mediterranean Sea.

Geologists Daoyuan Sun from the University of Science and Technology of China and Meghan Miller from the Australian National University highlighted the occurrence of five significant deep-focus earthquakes near Granada, Spain, since 1954. These earthquakes originated at depths exceeding 600 kilometers.

An analysis of the 2010 earthquake in Spain provided further insights into this unique seismic activity. Unlike typical deep earthquakes, which often lead to significant aftershocks, the 2010 event in Spain did not produce any. This anomaly is linked to the behavior of tectonic plates during subduction, where one plate is forced under another. This process can either destroy the subducting plate, leading to the formation of mountains and the locking of plates together, or result in the plates remaining distinct yet stacked, with one plate gradually descending into the Earth’s mantle.

The specific dynamics of the African and Eurasian plate boundary, where the Mediterranean seabed is being subducted beneath Europe, were observed during the 2010 Granada earthquake. The seismic waves from this earthquake exhibited an extended duration and an additional phase of activity due to their slower movement at the bottom of the Alboran slab, rather than at the top.

Geologists Sun and Miller noted that the seismic activity suggested a significant transfer of water to the mantle transition zone, indicative of a relatively cold slab. The cool temperature of the slab, despite the western Mediterranean’s relatively young seafloor age, implies a rapid subduction pace, estimated at around 70 millimeters per year. This study sheds light on the complex interactions between tectonic plates and their impact on seismic activity in regions like Spain.