Impact of 2019 Earthquakes on Shallow Aquifers in Northern sub-Himalayan Pakistan: A Detailed Analysis of Mirpur and Surrounding Areas

In 2019, a series of earthquakes struck the northern sub-Himalayan region of Pakistan, with the Mirpur earthquake triggering extensive coseismic liquefaction-induced surface deformations, such as sand blows, ground failure, and lateral spreading along the upper Jhelum Canal (UJC). A total of thirty-two vertical electrical sounding (VES) sites were acquired to investigate the deeper aquifer system in the region. An electrical resistivity tomography (ERT) survey was conducted along the canal to comprehensively delineate the subsurface conditions associated with the coseismic liquefaction phenomenon in the epicentral region. To address the water quality after the earthquakes, physiochemical analysis was also performed on twenty-four water samples collected from the tube wells and shallow water wells across the study area. The VES data reveals that the lithological units consist of thick layers of sandy clay, sand, and sand with gravel. The iso-resistivity map and hydrochemical analysis reflects fresh groundwater potential at a depth of about 100m. The ERT profiles identified a low resistivity (<10Ωm) saturated layer of clay that is about 20m thick. This saturated layer records the rise in groundwater level and contributes to liquefaction and land subsidence during an earthquake. The higher values of turbidity in shallow water samples document deterioration of water quality due to multiple earthquake tremors. The sandy aquifer units present at deeper levels are highly recommended for drinking purposes and domestic usage.