秦岭北麓晚第四纪断层陡坎的初步研究

根据航片解译和野外调查,发现在秦岭北麓第四纪松散沉积物中发育有断层陡坎,本文依据对这些陡坎的地质地貌分析、地形剖面测制、探槽揭露及测年数据,讨论了断层陡坎的空间分布和形态学特征、生成时代和断距,评估了秦岭北麓断裂在晚第四纪的活动强度。由断层陡坎高度经过校核获得断距变化范围在1.1至7.9米之间,由此求得秦岭北麓断裂中段全新世中晚期以来平均滑动速率接近1mm/a,西段在眉县一带为0.5mm/a左右。晚更新世以来,发生过3—4次古地震事件

PRELIMINARY STUDY ON LATE QUATERNARY FAULT SCARPS ON THE NORTHERN PIEDMONT OF QILING MOUNTAIN

Interpretation of aerophotoes and field investigation make authors find that a series of fault scarps are distributed in the .unconsolidated Quaternary sediments on the northern piedmont of Qinling Mts. Further geological, geomorphological and chronological studies of the fault scarps in combination with the analysis of levelled morphological sections of the scarps and excavated trenches led us to reveal the spatial distribution, geometric features, ages and offsets of the fault scarps and the activity of the northern piedmont fault of Qinling Mountain in late Quatery. It is indicated that the fault scarps occurred and were preserved on special tectonic and geomorphic parts of the zone. The heights of the scarps range from 1.1m to 7.7m, but the scarps on elder morphological surfaces are higher than those on younger morphological surfaces. The average slip rate along the middle segment of the northern piedmont fault in late Holocene is about 1mm/a, while that along the western segment of the fault is about 0.5mm/a. Three or four large paleoseismic events probably occurred on the northern piedmont fault since late Pleistocene.