Influence of Anthropogenic Groundwater Unloading in Haouz Plain on the 8 September 2023 Mw 6.8 Al Haouz, Morocco Earthquake

ABSTRACT We explore the possible relationship between anthropogenic crustal unloading, induced by groundwater extraction in the Haouz plain surrounding region, and the occurrence of the 8 September 2023 Mw 6.8 earthquake in the High Atlas Mountains (Morocco). Groundwater extraction from unconfined shallow aquifers surrounding Marrakesh in the Haouz plain surpasses aquifer replenishment, resulting in a noticeable reduction in mass. This anthropogenic crustal unloading potentially induces prolonged fault slip or influences seismic potential in the neighboring slowly deforming High-Atlas Mountain region, and associated critically stressed fault system. Our comprehensive study, integrating geodetic data, Interferometric Synthetic Aperture Radar observations and modeling, hydrological proxies, and coupled poromechanical model suggests a probable connection between anthropogenic groundwater unloading in the Haouz plain and the occurrence of the deadliest 2023 Mw 6.8, Al Haouz, Morocco earthquake. The unregulated extraction of groundwater in the Haouz plain introduces a significant increase in up-dip shear stress at the seismogenic depth, explicitly on a slowly deforming High-Atlas Mountains in western Morocco. The increased stress contributes to the ongoing interseismic tectonic loading on the steeply dipping Tizi n’Test fault and might have led to a significant clock advance for the 2023 Mw 6.8 2023 Al Haouz, Morocco earthquake. Therefore, an unforeseen change in the natural underground stress conditions caused by human activity on a dynamic earthquake-producing fault offers new understanding of the risk of human-triggered earthquakes in western Morocco.