Hidden thrust & strike-slip faults As the most important linear seismic sources in Zagros

Although there are several types of surface faults in Zagros simple folded belt (south west of Iran) but majority of earthquakes epicenter distribution in this part of Zagros are located without any relation with surface ruptures, this subject emphasizes that active master blind faults are exist as hidden linear seismic sources.Master blind faults in Zagros are divided into two groups; thrust and strike-slip. Trend of blind thrust faults is more and less parallel to folds axis, whereas hidden strike-slip faults generated in basement and they have generally northeast-southwest to north-south trend and normally their movement effect folds.Thrust faults themselves divide into two groups. First ones are including basement thrust faults; they generated from basement and could cut some part of sedimentary cover, but they could not reached to surface so far. Second group are related to folds. The faults of this group are located under neutral surface of folding, although in the most area of simply folded belt they are hidden, but in a few folds they could reach to surface. Trace of strike-slip basement hidden faults can be detected based on large scale studies on satellite images. In this case they can distinguish by some items including; any rotation along folds axis, salt plugs distribution, earthquake epicenters distribution, geomorphology and etc.If master blind faults are ignored in seismotectonics studies, seismic parameters for different earthquake level will be determined much less than their true values. This article attempts, by giving some examples, to present and depict the significance of the hidden faults evaluation and related hazard on major projects such as dams and Hydropower plants in simply folded belt that their damages leading to loss of human and wasting a lot of financial resources.

کلیدواژه ها:

Zagros ، Simply folded belt ، Hidden fault