Kohistan-Chilas area in northern Pakistan has experienced few damaging earthquakes for recent few decades that showed the current active crustal movement.
This study is mainly aimed to understand the relation of tectonic stress field and active faults in Kinki Triangle and to compare it with those of Kohistan-Chilas area. It is also aimed to confirm the relationship between geomorphologic evidence detected by the interpretation of aerial photographs and structural behavior of the geological units surveyed in the field.
Throughout the study of eleven active faults in Kinki-Triangle this relationship has been confirmed. It is revealed also that the active faults there are grouped into three: those along Median Tectonic Line (MTL), those of left lateral motion having NW(NNW)-SE(SSE) strike and those of right lateral having NE(NNE)-SW(SSW) strike. The latter two can be summarized by the tectonic stress of E-W compression. Namely they are conjugate shear faults. It has been said for long time that this regional stress might be caused by subducting Pacific Plate. The recent studies, however, show a possible alternative cause, i.e., the irregularly shaped subducting Philippine Sea Plate.
These two areas show a similarity in the tectonic frame work of the compressive regional tectonic stress and the accompanying conjugate shear faults systems. The existence of other tectonic units, however, makes them different each other.
Therefore, it is necessary to conduct systematic studies of active faults in Kohistan, northern Pakistan not only by the conventional geological survey but also by the geomorphologic interpretation of aerial photographs combined with field survey including trench observation.