Severe earthquake and tsunami will devastate Andalusia in Spain, scientists warn

A new study led by the Institute of Marine Sciences (ICM) has shown that thrust faults have more potential to generate tsunamis in the coastal zone than previously thought.

New data from the offshore Averroes Fault in the Alboran Sea show that a major earthquake (M7.0) is brewing in this seismic zone, which in turn will generate a tsunami 6 meters high that could partially destroy and inundate the Andalusian coast.

“These giant waves could pose a threat to coastal populations, damage marine and land infrastructure, and cause an economic and environmental crisis. These results will be important to improve planning measures to mitigate the effects of a possible tsunami,” explains ICM geologist Ferran Estrada.

Tsunamis are caused by sudden shifts in the seafloor and are usually triggered by seismic activity on normal and reverse faults. However, strike-slip faults, which separate laterally moving blocks, are usually excluded as tsunami triggers.

“The Averroes Fault has a vertical surge of up to 5.4 meters at its northwest end that could trigger a strong magnitude 7 earthquake. We have studied the activity of the fault over the past 124,000 years, and historical records show that the last earthquake caused by the fault occurred in 365 AD,” Estrada adds.

Thanks to a mathematical model of seafloor deformation, the research team was able to calculate the behavior of water masses in the Alboran Sea in the event of a new seismic episode on the fault.

According to this modeling of possible scenarios, tsunami waves would have spread along two main branches and would have reached and flooded densely populated sectors of the southern coast of Spain and northern Morocco.

These waves could have been as high as six meters and would have taken 21 to 35 minutes to reach the coast.

“These are too fast episodes for existing early warning systems to be successful. These results show that the potential of tsunami-generating strike-slip faults should be considered when reevaluating tsunami early warning systems,” concludes the ICM researcher.

Here’s an abstract of the article in the journal Nature:

“Tsunamis are caused by sudden shifts in the seafloor and usually result from seismic activity on faults. However, strike-slip faults are not usually considered to be major triggers because they are thought to be capable of generating only moderate seafloor deformation; accordingly, the tsunamigenic potential for vertical discharge at the tops of strike-slip faults is not considered significant.

“We found that the active northwest-southeast dextral Averroes fault in the central Alboran Sea (westernmost Mediterranean) has a historical vertical setback of up to 5.4 m at the northwestern tip, consistent with a Mw 7.0 earthquake.

“We modeled the tsunamigenic potential of this seafloor deformation using the Tsunami-HySEA program using the Coulomb 3.3 code. The waves propagating along the two main branches reached densely populated sectors of the Iberian coast with a maximum arrival height of 6 m within 21 and 35 minutes, too fast for existing early warning systems to be successful.

“These results suggest that the tsunamigenic potential of strike-slip faults is more important than previously thought and should be considered when re-evaluating tsunami early warning systems.”

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