GEOMORPHOLOGY AND STRUCTURE OF THE JID FAULT, MONGOLIAN ALTAI

The Jid Fault is a 60-km long right-lateral strike-slip fault. A 15-km long section of the fault between N49º27'32.6” and E91º43'25.1” appears to be almost pure right-lateral strike-slip to the north with a thrust component introduced further south as the fault changes orientation from trending north-south to northwest-southeast. At this change in orientation, the fault splits into three north-south splays. The westernmost segment appears to be mostly right-lateral strike-slip while the middle segment has a normal component of motion. The eastern segment follows an anticlinal ridge and has a thrust component. The three parallel fault strands probably form a flower structure of numerous fault strands narrowing into a single oblique strike-slip fault at depth. Well-preserved earthquake ruptures take the form of alternating tension cracks and pressure ridges which represent failure of the top few meters of soil cover in response to strike-slip motion at depth. Extension fractures in areas where the fault has a substantial thrust component are caused by collapse of the scarp.