The Late Quaternary slip rate along the Maqu segment of the eastern Kunlun Fault was estimated using a combination of high-resolution remote sensing imagery interpretation, field observations and differential Global P...The Late Quaternary slip rate along the Maqu segment of the eastern Kunlun Fault was estimated using a combination of high-resolution remote sensing imagery interpretation, field observations and differential Global Positioning System（GPS） measurements of offset river terraces, and 14 C dating of snail shells collected from offset risers. The results show that the left-slip rate along the segment is 3–5 mm/a, and that the vertical slip rate is 0.3–0.5 mm/a. Both the horizontal and vertical slips on the segment remain consistent over a distance of ~100 km. It means that no slip gradient as previously suggested occurred along the Maqu segment, and which thus might behave as an independent seismogenic fault. Judging from multiple relationships among young terrace offsets, we infer that co-seismic surface rupture produced by a characteristic earthquake with a magnitude of Ms7.0–7.5 on the Maqu fault could generate a horizontal slip of 4.5–5 m and a vertical slip of 0.45–0.5 m, with a corresponding ratio（Dh/Dv） of about 9. Two surface rupture events must have occurred over the past 3300 years, the latest one possibly between 1485 cal BP and 1730 cal BP.展开更多
Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, whi...Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, which have caused significant deterioration of the eco-environment in this region. In order to restore the ecological environment, a government project to restore the grazing areas to grassland was implemented in Maqu County in early 2004. This study evaluates the effects of that restoration project on land use and land cover change （LUCC）, and explores the driving forces of LUCC in Maqu County. In the study we used Landsat images obtained in 1989, 2004, 2009, and 2014 to establish databases of land use and land cover. Then we derived LUCC information by overlaying these layers using GIS software. Finally, we analyzed the main forces responsible for LUCC. The results showed that forests, high-coverage grasslands, and marshes experienced the most significant decreases during 1989–2004, by 882.8 ha, 35,250.4 ha, and 2,753.4 ha, respectively. However, moderate- and low-coverage grasslands and sand lands showed the opposite trend, increasing by 12,529.7 ha, 25,491.0 ha, and 577.5 ha, respectively. LUCC in 2004–2009 showed that ecological degradation slowed compared with 1989？2004. During 2009–2014, high- and moderate-coverage grasslands increased obviously, but low-coverage grasslands, marshes, unused lands, sand lands, and water areas showed the opposite trend. These results suggested that the degradation of the eco-environment was obvious before 2009, showing a decrease in the forests, grasslands, and water areas, and an increase in unused lands. The ecological degradation was reversed after 2009, as was mainly evidenced by increases in high- and mod-erate-coverage grasslands, and the shrinkage rate of marshes decreased obviously. These results showed that the project of restoring grazing lands to grassland had a positive effect on the LUCC. Other major factors that influence the LUCC include increasing temperature, variation in the seasonal frozen soil environment, seasonal overgrazing, and pest and rodent damage.展开更多
基金support of the Natural Science Foundation of China(41472178)the China Geological Survey projects(1212011120167,12120114002211)
文摘The Late Quaternary slip rate along the Maqu segment of the eastern Kunlun Fault was estimated using a combination of high-resolution remote sensing imagery interpretation, field observations and differential Global Positioning System（GPS） measurements of offset river terraces, and 14 C dating of snail shells collected from offset risers. The results show that the left-slip rate along the segment is 3–5 mm/a, and that the vertical slip rate is 0.3–0.5 mm/a. Both the horizontal and vertical slips on the segment remain consistent over a distance of ~100 km. It means that no slip gradient as previously suggested occurred along the Maqu segment, and which thus might behave as an independent seismogenic fault. Judging from multiple relationships among young terrace offsets, we infer that co-seismic surface rupture produced by a characteristic earthquake with a magnitude of Ms7.0–7.5 on the Maqu fault could generate a horizontal slip of 4.5–5 m and a vertical slip of 0.45–0.5 m, with a corresponding ratio（Dh/Dv） of about 9. Two surface rupture events must have occurred over the past 3300 years, the latest one possibly between 1485 cal BP and 1730 cal BP.
基金the funding received from the Natural Science Foundation of China (41301003, 41371026, and 31470480)the Technology of the People's Republic of China (No. 2013CB956000)
文摘Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, which have caused significant deterioration of the eco-environment in this region. In order to restore the ecological environment, a government project to restore the grazing areas to grassland was implemented in Maqu County in early 2004. This study evaluates the effects of that restoration project on land use and land cover change （LUCC）, and explores the driving forces of LUCC in Maqu County. In the study we used Landsat images obtained in 1989, 2004, 2009, and 2014 to establish databases of land use and land cover. Then we derived LUCC information by overlaying these layers using GIS software. Finally, we analyzed the main forces responsible for LUCC. The results showed that forests, high-coverage grasslands, and marshes experienced the most significant decreases during 1989–2004, by 882.8 ha, 35,250.4 ha, and 2,753.4 ha, respectively. However, moderate- and low-coverage grasslands and sand lands showed the opposite trend, increasing by 12,529.7 ha, 25,491.0 ha, and 577.5 ha, respectively. LUCC in 2004–2009 showed that ecological degradation slowed compared with 1989？2004. During 2009–2014, high- and moderate-coverage grasslands increased obviously, but low-coverage grasslands, marshes, unused lands, sand lands, and water areas showed the opposite trend. These results suggested that the degradation of the eco-environment was obvious before 2009, showing a decrease in the forests, grasslands, and water areas, and an increase in unused lands. The ecological degradation was reversed after 2009, as was mainly evidenced by increases in high- and mod-erate-coverage grasslands, and the shrinkage rate of marshes decreased obviously. These results showed that the project of restoring grazing lands to grassland had a positive effect on the LUCC. Other major factors that influence the LUCC include increasing temperature, variation in the seasonal frozen soil environment, seasonal overgrazing, and pest and rodent damage.
