Near-surface resistivity structure near avcilar landslide in İstanbul, Turkey by 2D inversion of VLF data

Abstract

In this study, VLF data collection and 2D modeling is carried out in order to gather information about the Avcılar landslide and to detect possible faults, may be residing in the study area, located at the southwestern slopes of the Küçükçekmece Lake in Avcılar, İstanbul, Turkey.Data collection is realized on 12 traverses in TE mode between 2015 and 2017 and mostly consists of in-phase and quadrature components of the tipper data. On a single profile, apparent resistivity and phase data is also collected. The study area is placed near an urban area and relatively higher noise levels are observed at several profiles. However, data in adjacent and overlapping profiles shows consistency and repeatability. Thus, instead of omitting these profiles, the data with higher noise is treated with Empirical Mode Decomposition (EMD) filtering.Karous-Hjelt filtered in-phase component data is calculated for basic interpretation, and 2D inversions are performed in order to obtain more information about the shallow geo-electrical structure. The approximate resistivities of the near-surface geological formations are differentiated from the recovered models. Accordingly, 2D inversion results suggest resistivity values significantly different from the values previously obtained using 1D methods. Inversion results also revealed the structure and the base of the Avcılar landslide successfully. In the northern part of the study area, the top of the Gürpınar formation, forming the base of the Avcılar landslide, is detected with varying depths up to 25 m. In the resistivity images any structure that may represent a fault is not detected.