Geomagnetic observations related with fault activity along the western part of the North Anatolian fault zone

Abstract

In order to investigate changes in geomagnetic field associated with seismic activitiesalong the western part of the North Anatolian Fault Zone, it is necessary to revealfirst, local geomagnetic variations. Therefore, observations of the geomagnetic totalintensity were carried out at the iznik-Mekece fault of the North Anatolian Fault Zone(NAFZ).First of all, it was conducted magnetic profile mesurements to define the faulttrace and its features. Taking into account the results of this measurements withthe others before, seven continuous and twenty-three repeat sites were set up in thiswork and it was tried to reveal the local geomagnetic variations for this zone. Simpledifferences technique is used to get local geomagnetic changes and it was seen that thesechanges were in the expected range and it would be helpful in detection of anomalousphenomena associated with earthquake occurrences.Inversion analysis of magnetic anomalies at the N AFZ suggest a dike-like structureextending parallel to the strike of the fault. Theoretical studies imply that changes inthe total intensitiy associated with fault activity are larger in the case of non-uniformdistribution of rock magnetization than those in the uniform case.Theoretical estimation of geomagnetic changes is made for the case of a magneticdike structure intruding a non-magnetic body parallel to the strike of a fault. It turnsout that the magnetic field arising from stress-induced magnetization enhanced.The obtained results from the repeat measurements show the geomagnetic local 'secular variation in this fault zone which would be possibly contribute to the understandingof an underground process related to the crustal activity.