山东汤头断层全新世右旋走向滑动的新证据

THE DISCOVERY OF DEXTRAL STRIKE-SLIP IN HOLOCENE ALONG THE TANGTO FAULT IN SHANDONG PROVINCE

汤头断层的断层陡坎长36公里,坎高1至3米,东升西降。断层陡坎与白垩系砂岩和太古界片麻岩之间的断层位置大致吻合。汤头断层居泉庄处,长1.1公里范围内,有12条近东西向冲沟被三条左阶羽列断层右旋扭错,出现冲沟直角扭曲及断头断尾现象,扭错距离3至25米。断层的扭错量中间大,两端小。位于一冲沟水平扭错处距现今沟底2米处淤泥层的发现,表明该断层的最新走滑活动发生在距今3681年以后。

The fault scarp of the Tangto fault is 36 km long, 1 to 3m high, striking NE15°. Its east side has been uplifted. The fault scarp in ground surface approximately is along the fault face that consists of Cretaceous sandstone and Archaean gneiss. Twelve gullies which strike nearly EW were dislocated in right lateral mode by three left-stepping echelon secondary faults in 1.1km distance, in the vicinity of Juquan village, where the gullies are contorted with right angle or their lower and upper reaches are offset. The horizontal dislocation is 3-25m. The biggest is in middle, the smaller is in either end of the fault in one of the three secondary fault. In a place along the fault, it has been discovered that the peat which has a few square metre has been uplifted. Its position is about 2.0m to the bottom at present. It is considered that the peat was the early sediment in the pool along the fault scarp. The 11G dating of the peat is 3681 a B.P. and two faulting can be shown. One occurred before 3681a probably and the other is the dextral strike slip faulting occurring in last 3681a. If creep-slip is not in consideration, two earthquake events would have occurred since Middle-Late Holo-cene.