Meric Aziz Berge

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.

The investigation of faults in active tectonic regions is of great importance in geosciences, and geophysical methods play a key role in their detection. In particular, determining subsurface characteristics related to faults and identifying palaeoseismological trench locations using geophysical methods are topics of significant research interest to researchers. The very low frequency electromagnetic (VLF-EM) method is one of the geophysical techniques employed to investigate such problems. This study presents the results of simulation and field investigations using the VLF-EM method for fault detection. The well-established Fraser and Karous–Hjelt filters, which are widely used and effective for fault detection, were applied to the VLF-EM data. Moreover, the in-phase and quadrature components of both synthetic and field data sets were inverted to obtain the subsurface resistivity distribution. This enabled the interpretation of shallow subsurface resistivity distribution in relation to fault characteristics. A simulation was carried out to demonstrate the importance of selecting an appropriate initial value for the inversion algorithm. In addition, denoising of the VLF-EM data was investigated using the noise-assisted multivariate empirical mode decomposition technique, which yields more accurate inversion results by effectively eliminating noise. The intrinsic mode functions obtained from the decomposition process were used to identify both the noise and the trend within the VLF-EM data. The performance of the denoising procedure prior to inversion is presented for four field datasets acquired around the city of İzmir. The inversion results of the field datasets revealed that lateral resistivity variations can be traced in the two-dimensional sections and are associated with near-surface faults. The identified faults extend to the surface and provide crucial information on the presence of active faulting in the study areas. Thus, the efficiency of the VLF-EM method for fault investigation has been demonstrated.

In this paper, an integrated geophysical investigation of a sacred area in the archaeological site of Šapinuwa is presented. Šapinuwa was one of the important cities in the Hittite Empire. The archaeological site of Šapinuwa is located in the Çorum region of Central Anatolia, Turkey. The goal of the here presented integrative archaeological prospection investigation was to explore buried structures inside the so‐called sacred Taşdöşem area (Taşdöşem means “the stone pavement”) by employing a number of different near‐surface geophysical prospection methods. To this purpose, magnetic gradiometry, ground‐penetrating radar, electrical resistivity tomography, seismic refraction tomography, and multi‐channel analysis of surface wave tomography were applied in this specific area. Overall, the results of the individual geophysical investigations were superimposed in order to obtain more detailed and comprehensive integrative interpretations on the burials contained inside this sacred area. Electrical tomography depth slices revealed the presence of an important structure buried inside the Taşdöşem area. Surprisingly, the velocity variations observed in the depth slices of the multi‐channel analysis of surface wave tomography provided important information on the character of the burial structure. Additionally, seismic refraction tomography sections and depth slices confirmed the presence of the structures in the same locations. The result of the ground‐penetrating radar investigation did not present sufficient certainty regarding the possible deeper burials, whereas the magnetic gradiometry survey gave some insight into near‐surface structures. The combination of the employed geophysical prospection techniques was successfully able to characterize the structures that are assumed to have been buried within the Taşdöşem area. It is concluded that the integrated non‐invasive geophysical archaeological prospection study conducted at Šapinuwa provides a good example on how to approach the investigation and documentation of sites similar to the Taşdöşem.

To determine the data acquisition and inversion capabilities of electrical resistivity tomography (ERT), which is used in multilayered archaeological settlements, an ERT survey was carried out at the Old Smyrna Höyük site, in the city of İzmir, Turkey. This site dates from the third millennium bc and ERT applications were performed using five different arrays (Wenner–alpha, Wenner–Schlumberger, dipole–dipole, pole–pole and pole–dipole). The resistivity distribution of the subsurface was investigated by two‐dimensional and three‐dimensional inversion routines, which use data obtained along orthogonal lines. To test the inversion treatments, ‘semi‐fully three‐dimensional’ and ‘quasi‐three‐dimensional’ approaches were also investigated, and comparison indicated a clear distinction between them. The results show that the quasi‐three‐dimensional solution had insufficient resolution, whereas the semi‐fully three‐dimensional data sets provide interpretable images of the subsurface. In addition, the effects of electrode array type and line interval and orientation were tested to define suitable ERT survey strategies for multilayered archaeological settlements. The array investigations show that dipole–dipole, pole–pole and pole–dipole arrays presented better quality images than the others. The line orientation tests performed in two perpendicular directions (N–S and E–W oriented lines) show that the N–S oriented lines are more suitable in terms of defining the buried architectural plan of Old Smyrna Höyük according to depth‐slicing visualizations. However, the combination of the two perpendicular data sets could be useful if large between‐line intervals are used. Finally, this ERT study clearly revealed the layered stratigraphy of Old Smyrna Höyük. Copyright © 2011 John Wiley & Sons, Ltd.