ANALYSIS OF THE STRUCTURAL STRESS FIELD OF THE QIANGTANG BASIN

EW-trending folds and reversed(thrust) faults and NW-and NE-trending strike-slip faults predominate in the Qiangtang basin in the interior of the Qinghai-Tibetan Plateau,and occasionally NW-and NE-trending folds and nearly N-S-trending normal faults my be found.Based on the structural combination analysis,structural analysis,mathematical calculation and finite element modeling,it is revealed that the orientation of the maximal principal stress of the structurally deformed stress field in the basin is nearly north-south,with attendent NW-SE,NE-SE and nearly E-W orientations,which indicates that the basin has long undergone N-S strong compression since the Indosinian movement,accompanied by intermittent(or derivative) NE-SW,NE-SE and nearly E-W compression.