Active Faulting and Segmentation along Qom-Zefreh Fault System between Zerfreh and The North of Kashan, Central Iran

The N-NW trending Qom-Zefreh fault system has long been recognized as one of the major faults in Central Iran. We have used observations of faulting, recognized on satellite images and aerial photos, in conjunction with field investigations, to infer fault activity along this structure in an area between Zefreh and the north of Kashan. Right-lateral strike-slip motion along this fault can be inferred from the associated lateral offset of stream beds and alluvial fan observed on aerial photographs and on the field. Morphological features and observations of fault exposure in several places also indicate that the western block is up-thrown relative to the eastern block across reverse component of the Qom-Zefreh fault system. Using changes in fault geomorphology and fault trace orientation we have defined two segment boundaries and structurally divided the Qom-Zefreh fault system into three segments in the region, namely Zefreh, Kashan and Ravand segments. The recognition of these segments is important because it may have implication in assessment of seismic hazard for the Kashan region.