Archaeogeophysical exploration in Neuss‐Norf, Germany using electrical resistivity tomography and magnetic data

Abstract

A combination of electrical resistivity tomography (ERT) and magnetic gradiometry was selected to examine a hypothesis concerning the presence of remains of one of the oldest archaeological churches in the Rhineland, located in Neuss‐Norf, Germany. The gradiometer survey was carried out to measure the vertical gradient of the magnetic field using a proton precession magnetometer along several profiles. The magnetic data were reduced to the magnetic pole; then analytic signal and power spectrum techniques were applied. The ERT survey was based on the magnetic results, and both Wenner and dipole–dipole configurations were employed to collect the apparent resistivity data along 12 ERT profiles. The field ERT data from these two arrays were merged into one dataset to form a non‐conventional mixed array. The robust (blocky) inversion technique was applied to the resistivity data in order to derive the two‐dimensional resistivity distribution of the subsurface. Despite the noisy surroundings, the magnetic survey was able to give an indication of potential walls of the ancient church in addition to several subsurface magnetic sources. Moreover, highly resistivity anomalies were observed within the first 1–2 m of the subsurface soil and were interpreted as possible remains of man‐made structures. This depth range was also confirmed by the spectral analysis of the magnetic data. A strong consistency between the two methods was observed in some locations of the site. In addition, the ERT measurements confirm and complement most of the magnetic results. We successfully detected anomalous zones that could be associated with the walls of at least one ancient church building in addition to several possible archaeological structures in the survey area.

Research on the Monitoring of Overlying Aquifer Water Richness in Coal Mining by the Time-Lapse Electrical Method

“…It analyzes the change rule of the electrical properties of the coal strata caused by coal seam mining by comparing the differences in the electrical resistivity of the data from multiple detections. At the same time, in this study, referring to the past research experience and the application experience in the actual experiment, this paper adopts the Quasi-Newton method inversion [25]. Because the Quasi-Newton method only needs the gradient information of the objective function and does not need to calculate the sensitivity matrix explicitly, the number of forward simulations required in each inversion iteration is less.…”