For the first time on the Chinese mainland, long-range wide-angle seismic reflection/refraction profiling technology has been applied to seismic wave phases from different depths and with different attributes within t...For the first time on the Chinese mainland, long-range wide-angle seismic reflection/refraction profiling technology has been applied to seismic wave phases from different depths and with different attributes within the various blocks of the North China Craton to characterize the structure of the crust and upper mantle lithosphere. By comparative analysis of the seismic wave phase characteristics in each block across a 1500-km-long east-west profile, we have identified conventional Pg, Pci, PmP and Pn phases in the crust, made a clear contrast between PL1 and PL2 waves belonging to two groups of lithospheric-scale phases, and produced a model of crust-mantle velocity structures and tectonic characteristics after one- and two-dimensional calcula- tions and processing. The results show that the thickness of the crust and lithosphere gradually deepens from east to west along the profile. However, at the reflection/refraction interface, seismic waves in each group show obvious localized changes in each block. Also, the depth to the crystalline basement changes greatly, from as much as 7.8 km in the North China fault basin to only about 2 km beneath the Jiaodong Peninsula and Taihang-Ltlliang area. The Moho morphology as a whole ranges from shallow in the east to deep in the west, with the deepest point in the Ordos Block at 47 km; in contrast, the North China Plain Block is uplifting. The L1 interface of the lithosphere is observed only to the west of Taihang Mountains, at a relatively slowly changing depth of about 80 km. The L2 interface varies from 75 to 160 km and shows a sharp deepening to the west of Tai- hang Mountains, forming a mutation belt.展开更多
To evaluate and provide an appropriate theoretical direction for research into climate-vegetation interactions using meteorological station data at different time scales,we examined differences between the Normalized ...To evaluate and provide an appropriate theoretical direction for research into climate-vegetation interactions using meteorological station data at different time scales,we examined differences between the Normalized Difference Vegetation Index (NDVI)and Enhanced Vegetation Index (EVI)and their responses to climate factors. We looked for correlations between'data extracted from MOD13Q1 remote sensing images and meteorological station data for the two indexes.The results showed that even though NDVI and EVI are derived from the same remote sensing image,their response to climate factors was significantly different.In the same meteorological station,the correlation coefficients for NDVI,EVI and climate factors were different;correlation coefficients between NDVI,EVI and climate factors varied with meteorological station.In addition,there was a lag effect for responses of NDVI to average minimum temperature,average temperature,average vapor pressure,minimum relative humidity, extreme wind speed,maximum wind speed,average wind speed and average station air-pressure.EVI had a lag only for average minimum temperature,average vapor pressure,extreme wind speed,maximum wind speed and average station air-pressure.The lag period was variable,but most were in the -3 period.Different vegetation types had different sensitivities to climate.The correlation between meteorological stations and vegetation requires more attention in future research.展开更多
基金supported by the Key Project of the National Natural Science Foundation of China (Grant No. 90814012)the High-tech Project of the National Development and Reform Commission (Grant No. B08030)the Spark Program of Seismic Science and Technology
文摘For the first time on the Chinese mainland, long-range wide-angle seismic reflection/refraction profiling technology has been applied to seismic wave phases from different depths and with different attributes within the various blocks of the North China Craton to characterize the structure of the crust and upper mantle lithosphere. By comparative analysis of the seismic wave phase characteristics in each block across a 1500-km-long east-west profile, we have identified conventional Pg, Pci, PmP and Pn phases in the crust, made a clear contrast between PL1 and PL2 waves belonging to two groups of lithospheric-scale phases, and produced a model of crust-mantle velocity structures and tectonic characteristics after one- and two-dimensional calcula- tions and processing. The results show that the thickness of the crust and lithosphere gradually deepens from east to west along the profile. However, at the reflection/refraction interface, seismic waves in each group show obvious localized changes in each block. Also, the depth to the crystalline basement changes greatly, from as much as 7.8 km in the North China fault basin to only about 2 km beneath the Jiaodong Peninsula and Taihang-Ltlliang area. The Moho morphology as a whole ranges from shallow in the east to deep in the west, with the deepest point in the Ordos Block at 47 km; in contrast, the North China Plain Block is uplifting. The L1 interface of the lithosphere is observed only to the west of Taihang Mountains, at a relatively slowly changing depth of about 80 km. The L2 interface varies from 75 to 160 km and shows a sharp deepening to the west of Tai- hang Mountains, forming a mutation belt.
基金National Key Research and Development Program of China(2016YFC0501003)
文摘To evaluate and provide an appropriate theoretical direction for research into climate-vegetation interactions using meteorological station data at different time scales,we examined differences between the Normalized Difference Vegetation Index (NDVI)and Enhanced Vegetation Index (EVI)and their responses to climate factors. We looked for correlations between'data extracted from MOD13Q1 remote sensing images and meteorological station data for the two indexes.The results showed that even though NDVI and EVI are derived from the same remote sensing image,their response to climate factors was significantly different.In the same meteorological station,the correlation coefficients for NDVI,EVI and climate factors were different;correlation coefficients between NDVI,EVI and climate factors varied with meteorological station.In addition,there was a lag effect for responses of NDVI to average minimum temperature,average temperature,average vapor pressure,minimum relative humidity, extreme wind speed,maximum wind speed,average wind speed and average station air-pressure.EVI had a lag only for average minimum temperature,average vapor pressure,extreme wind speed,maximum wind speed and average station air-pressure.The lag period was variable,but most were in the -3 period.Different vegetation types had different sensitivities to climate.The correlation between meteorological stations and vegetation requires more attention in future research.
