Abstract
Abstract. Several active faults affect the Central Alborz, Northern Iran. The main active faults in the region are the North Tehran and the Mosha faults and their westward continuation, the Taleghan fault. Among these the Mosha fault is the most active fault in Central Alborz. The piezomagnetic field has been inspired by many investigations in the earthquake prediction studies and has been reported in the literature. Several theories proposed for relating piezomagnetic changes into magnetic signals accompanying earthquakes in the vicinity of a fault. In this study based on an analytical solution for the elementary piezomagnetic potentials due to an inclined rectangular fault within a semi-infinite elastic medium a computer program has been developed. This program has been used for evaluation of the rotational piezomagnetic changes along the Mosha fault using different earthquakes with specific magnitudes and at the presence of three different geomagnetic main fields. The magnetic data acquired recently at the study area has been used during the modeling. The first result that can be inferred from this study is that rotational piezomagnetic anomalies are completely localized at the fault tips. So for detection of this anomaly the magnetic instruments should be installed at these locations. The other important element which has been investigated was the amount of slip along the fault, which shows anomaly intensification by increase in the amount of slip.
Highlights
The Mosha Fault, which was first identified by Dellenbach (1964), is the most prominent structure in the southern part of the Central Alborz (Fig. 1)
The magnetization of titanomagnetite-bearing rocks varies under the mechanical stress and consequent time-dependent local magnetic changes. This phenomenon which is known as piezomagnetic field has been inspired by many investigations in earthquake prediction studies and has been reported in the literature (Johnston and Muller, 1987; Sasai and Ishikawa, 1991; Johnston et al, 1994)
U denotes a dislocation vector, and ωkml expresses the elementary Piezomagnetic potential produced by the mth component of initial magnetization of the crustal rock at the fault zone. υl stands for a unit vector normal to the surface element d of the fault
Summary
The Mosha Fault, which was first identified by Dellenbach (1964), is the most prominent structure in the southern part of the Central Alborz (Fig. 1). The magnetization of titanomagnetite-bearing rocks varies under the mechanical stress and consequent time-dependent local magnetic changes This phenomenon which is known as piezomagnetic field has been inspired by many investigations in earthquake prediction studies and has been reported in the literature (Johnston and Muller, 1987; Sasai and Ishikawa, 1991; Johnston et al, 1994). It seems necessary to use other methods such as measuring rotational piezomagnetic changes in conjunction with total field studies to provide a new insight to the issue. Model calculations have been conducted in order to forecast the rotational piezomagnetic amplitudes in the case of the occurrence of an arbitrary earthquake along the fault This information along with the recently acquired magnetic data in the Mosha fault region (Mokhtari et al, 2008) will be used in installing the future magnetic data acquisition system. In this paper after a brief introduction of the methodology, through numerical modeling of piezomagnetic component for the Mosha fault will be discussed
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