The Induced Seismicity Effect in Morocco Caused by a Reduced Aquifers Volume according to Stacking-InSAR Method and Gravimetric Data

Abstract

The geodynamics at the epicenter of the destructive Mw = 6.8 earthquake that occurred in Morocco on September 8, 2023, was studied by the Stacking-InSAR method applied to 801 interferograms based on the Sentinel-1 synthetic aperure radar (SAR) data. Over the period from January 2019 to September 2023, local subsidence of the surface with an average velocity of 1.5 cm/yr was discovered. The maximum velocity obtained in 2023 reached 24 cm/yr in the areas with a developed melioration system located above aquifers. Based on the integrated analysis of variations in the water equivalent thickness measured from the 2000–2023 satellite gravimetric data and the amount of precipitation, the surface subsidence was found to be due to a significant withdrawal of water from aquifers. Assuming similar shapes of isoseists of earthquakes with close epicenters, the isoseists of the earthquakes that occurred in 2014 and 2023 were compared. The data obtained made it possible to identify the expansion of isoseist contours toward the descending surface areas of the 2023 earthquake. This process, along with the tectonic movements of the Eurasian and Nubian plates, is believed to have increased the stress–strain state between two aquifers and finally caused the Mw = 6.8 earthquake in Morocco on September 8, 2023.