TALAS-FERGANA FAULT: PRESENT DISPLACEMENTS IN THE TIEN SHAN NEAR THE CHATKAL RANGE

Abstract

The identical width and morphology of offset parts of the dry valley above and below the fault line indicate that displacements here occurred fast and, therefore, were earthquake induced. Since each offset valley has only one old extension, those displacements resulted from one strong earthquake, whose role in triggering them seems indisputable. However, available data do not exclude the possibility of slow movement (creep) along the fault. The observed landform displacements must have resulted from an older earthquake. Indeed, many traces of old earthquakes are already known near the Talas-Fergana fault. Methods of dating fault movements and a peat-soil layer are discussed. The work has shown that in historic time along the Talas-Fergana fault there was some displacement with a heave of 30 to 40 m and a small throw. It occurred (or started) in the earthquake that happened about 2000 years ago.