后差分GPS测量则木河断裂地震微地貌特征

地震微地貌是研究古地震的重要证据。发生在则木河断裂带上的1850年地震的地表破裂带在人类活动较少的地区得以保存完好。研究区内地形起伏大,断塞塘、断层陡坎、鼓包等微地震地貌特征明显,在三维视图内可直观反映测量区内的这些地貌特征。利用后差分GPS方法测量断裂活动形成的地震微地貌,水平测量精度可达0.5 m,DEM精度可到一个像元1m,是定量化研究地震微地貌的一种新方法。测量结果表明,大箐梁子顶部七条干沟对应多次古地震事件;大箐梁子顶部鼓包被断裂断错,断塞塘沉积区向南迁移,鼓包最新断错约4 m,大箐村南山坡形成50 cm高断层陡坎。说明大箐梁子一带地震活动性较强,且以挤压构造为主。

Micro geomorphology of Zemuhe Fault surveyed by virtue deferential GPS

Micro geomorphology is the key to study the paleoearthquakes The surface rupture caused by the earthquake occurred along Zemuhe river in 1850 was preserved in the almost uninhabited area.Micro geomorphology of the studied area,such as fault sag pond,scarp,pressured ridge and so on is easy to acquire and can be directly shown on the 3D image.We can use home deferential GPS to measure the geomorphology in this region,and can get the result with precision of half a meter horizontal,and one pixel one meter precision DEM.Virtual deferential GPS survey is a new method to quantitatively analyzed the micro geomorphology.We discover that the seven gullies correspond with several events;and the pressured ridge at the top of Daqingliangzi was cut by the fault,sedimental area of sag pond moved southward,most recent displacement is about 4m.We also find a scarp of 50cm south of Daqing village.It indicates that the seismicity around Daqingliangzi is more active than other segments,and many compressional structures are observed here.