Abstract:

A case DEM was extracted from IRS-P5 stereo images of middle three segments(Tuyou, Tuzuo and Bikeqi)in Daqingshan piedmont fault, and this DEMs vertical accuracy was tested to meet hilly-area and mountainous-region requirement of 1:10,000 topographic maps. Twenty-five gullies across the fault on the footwall have been extracted from this DEM, and the knickpoints caused by fault activities in Holocene have further been extracted from profiles of gullies, and the six-, five-and three-ranks of knickpoints are identified in the gullies from west to east. The newest rank knickpoints in the Tuyou and Tuzuo segments are regarded as those caused by the A.D.849 earthquake to get their retreat rates. The retreat rate of the newest knickpoint in each gully is also considered as that of other points in the same gully; the average retreat-rate value of the newest rank knickpoints in the Tuyou and Tuzuo segments is considered as that of the knickpoints in the Bikeqi segment; then the formation time of the six-, five- and three-ranks of knickpoints in the three segments is computed combining with the retreat distances of knickpoints on the gullies, thus the paleo-earthquake series in the study area in Holocene have been obtained. These paleo-earthquake series are close to the results that are derived from trench techniques and Holocene paleosols in paleo-alluvial-pluvial fans in previous studies.

Key words: IRS-P5, Daqingshan piedmont fault, DEM, knickpoint, paleo-earthquake