关键词: 则木河断裂, 地震微地貌, 后差分GPS, 地表破裂带, 活动速率

Abstract: 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.

Key words: Zemuhe fault, Micro geomorphology, virtual deferential GPS, Surface rupture, Slip rate