Magnetic anomalies around the North Anatolian Fault

Abstract

The nature of the observed magnetic anomalies surrounding the San Andreas fault (SAF) is of interest to researchers studying fault kinematics and earthquake dynamics. In this work we will present and interpret data collected around the North Anatolian fault (NAF) by Honkura et al. (1985) which exhibit anomalies similar to those observed along the SAF. Magnetic and surface geologic data from five profiles straddling the North Anatolian Fault were used in conjunction with a two dimensional magnetic inversion in an attempt to identify the source of the magnetic anomalies. As a result of this study, we conclude that all long wavelength anomalies (λ ≥ 500m) could be attributed to the changes in the relative magnetic susceptibility across geologic units. Thus, they are due to lateral variations in the near surface geology and are not due to the concentration of a particular material in the fault zone. However, there was one exception, a short wavelength anomaly (λ ≃ 150m) was observed on profile IJ. Based on the results of the inversion, it appears that the anomaly may be due to a small sliver of material located in the upper part of the fault zone. If that interpretation is correct, the short wavelength anomaly is clearly of different nature than the other anomalies.