Interpretation of integrated geophysical data for catchment identification in Western Türkiye (Soma, Manisa)

Abstract Groundwater exploration plays a crucial role in securing sustainable water resources, a fact that is particularly evident in the context of aquifers and catchments. It is imperative to comprehend the subsurface hydrological situation in order to identify the geological structures that control the occurrence and flow of groundwater. Hydrogeophysics is a comprehensive field that utilises geophysical methods to enlighten groundwater-related geological structures. This study presents the findings of an integrated geophysical investigation conducted in a catchment located within Kırkağaç Graben, western Türkiye. To image spatial distributions of subsurface electrical and seismic properties in both two and three dimensions, four complementary geophysical methods were employed: electrical resistivity tomography (ERT), direct current induced polarization (DCIP), self-potential (SP) and seismic refraction tomography (SRT). The catchment was therefore determined, and the interaction between fault and water discharge points was revealed by joint interpretation of the geophysical results. The ERT method yielded information about lithology-derived resistivity variations, while the DCIP method gave a strong response to clay content of geological units. Groundwater flow was predicted based on SP anomalies. Finally, the SRT data demonstrated the P-wave velocities indicating variable water saturation conditions in shallow geological layers. Notably, groundwater rising along the fault zone, which acts as a barrier, was delineated. Furthermore, the buried fault identified beneath the recent sedimentary deposits was interpreted as the youngest structural element of the graben. The findings underscore that the near-surface catchment is vulnerable to anthropogenic influences such as urbanisation and should therefore be subject to protection and sustainable management.