Previous studies have shown that reanalysis products contain large uncertainties in the Tibetan Plateau(TP),and the biases are location dependent.Therefore,these products must be evaluated with in situ observations pr...Previous studies have shown that reanalysis products contain large uncertainties in the Tibetan Plateau(TP),and the biases are location dependent.Therefore,these products must be evaluated with in situ observations prior to their applications.In this study,the authors compare the results of several reanalysis projects with independent sounding observations recorded in the Yarlung Tsangpo River valley in the Eastern Himalayas in June 2010.These reanalysis projects include Climate Forecast System Reanalysis(CFSR),Interim European Centre for Medium Range Weather Forecasts Reanalysis(ERA- Interim),Japanese 25-year Reanalysis(JRA-25),Modern Era Retrospective Analysis for Research and Applications(MERRA),National Center for Environmental Prediction and the Department of Energy Reanalysis 2(NCEP-R2),and NCEP Final Analysis(FNL).Statistical quantities such as average,mean bias(MB),root-mean-square difference(RMSD),and correlation coefficient(R) of temperature,specific humidity,u-wind,and v-wind between 100 hPa and 650 hPa were calculated.The authors determined that the performance of each product differed with variables at different levels.The average profiles of the variables were captured by the reanalysis products,with large biases appearing at lower levels.ERA-Interim and NCEP-R2 showed the best and worst performances,respectively,for all variables.This study suggests that users should select appropriate reanalysis products according to their specific purposes for TP research.展开更多
This study investigates the spatial and temporal variation of fractal dimension and b-value for the eastern part of the Himalaya and adjoining area(26°N–31°N and 87°E–98°E).The analysis is carrie...This study investigates the spatial and temporal variation of fractal dimension and b-value for the eastern part of the Himalaya and adjoining area(26°N–31°N and 87°E–98°E).The analysis is carried out on the earthquake dataset of 1373 events(Mc=4.0)by sliding window technique for the period 1964 to 2020.The region is divided into three sub regions A(87°E–92°E),B(92°E–94°E)and C(94°E–98°E).The b-value computed for the region A comprising eastern Nepal is smaller compared to other two regions which infers the possible high stress and asperities in the region.High spatial fractal dimension(Dc>1.5)and low temporal fractal dimension(Dt<0.31)are computed for the regions.High spatial fractal dimension may indicate that fractures generating earthquakes are approaching a 2D structure and low temporal fractal dimension implies high clustering of earthquake’s epicenters.The b value shows a weak negative correlation with Dc for regions A and C while a weak positive correlation is observed for the region B.Based on b-value and fractal dimension,this study explains the frequency of earthquakes and heterogeneity of the seismogenic structure in this part of the Himalaya.展开更多
Here we describe ductile, ductile-brittle and brittle deformation styles in the northern segment of the Tertiary Biluoxue- shan-Chongshan shear zone lying to the east of the Eastern Himalayan Syntaxis. In the northern...Here we describe ductile, ductile-brittle and brittle deformation styles in the northern segment of the Tertiary Biluoxue- shan-Chongshan shear zone lying to the east of the Eastern Himalayan Syntaxis. In the northernmost part of the zone in the vi- cinity of the Eastern Himalayan Syntaxis, it consists of mylonitic gneiss, granite, and schist. Based on field relations and min- eral assemblages, the rocks are classified into gneiss belt in the west limb, including banded gneiss, augen mylonite and mig- matite gneiss, and schist belt in the east limb. Except for the massive granite pluton, the other three tectonites are affected by polystage deformation （D1-D4）. Fold deformation of the first stage D1 is isoclinal to tight pattern with nearly N-S fold axes and steeply axial planar cleavage S 1, which resulted in the local crustal thickening under a contractive setting. D2 overprinted D1 and is characterized by tight folds with steep axes and N-S fold axial planar, which are also characterized by large-scale ductile strike-slip shear foliation $2, parallel to the nearly N-S trending axial planes of D1 and D2. The structural pattern of D2 represents a transpression along the zone. D3 occurred during the late stage of the transpression or post-transpression, produc- ing the NW-SE and NE-SW trending strike-slip faults of the third stage D3. Following the D3 deformation, the zone was ex- humed to shallow crustal level where the various tectonites underwent a brittle transtensional deformation D4, combined with one N-S trending strike-slip component and one normal faulting component. Structures and previous geochronologies pre- sented in the paper suggest that the study area is correlated with those in the adjacent tectonic zones, Ailaoshan-Red River shear zone and Gaoligong shear zone in the western Yunnan. It underwent intensive polyphase deformation, namely, crustal thickening, transpression, and transtension, responding to syn-collision and post-collision of India-Eurasia from 65 Ma to cur- rent period east of the Eastern Himalayan Syntaxis.展开更多
Polarization analysis of teleseismic data has been used to determine the XKS(SKS,SKKS,and PKS)fast polarization directions and delay times between fast and slow shear waves for 59 seismic stations of both temporary an...Polarization analysis of teleseismic data has been used to determine the XKS(SKS,SKKS,and PKS)fast polarization directions and delay times between fast and slow shear waves for 59 seismic stations of both temporary and permanent broadband seismograph networks deployed in the eastern Himalayan syntaxis(EHS)and surrounding regions.The analysis employed both the grid searching method of the minimum tangential energy and stacking analysis methods to develop an image of upper mantle anisotropy in the EHS and surrounding regions using the newly obtained shear wave splitting parameters and previously published results.The fast polarization directions are oriented along a NE-SW azimuth in the EHS.However,within the surrounding regions,the fast directions show a clockwise rotation pattern around the EHS from NE-SW,to E-W,to NW-SE,and then to N-S.In the EHS and surrounding regions,the fast directions of seismic anisotropy determined using shear wave splitting analysis correlate with surficial geological features including major sutures and faults and with the surface deformation fields derived from global positioning system(GPS)data.The coincidence between structural features in the crust,surface deformation fields and mantle anisotropy suggests that the deformation in the crust and lithospheric mantle is mechanically coupled.In the EHS,the coherence between the fast directions and the NE direction of the subduction of the Indian Plate beneath the Tibetan Plateau suggests that the lithospheric deformation is caused mainly by subduction.In the regions surrounding the EHS,we speculate that a westward retreat of the Burma slab could contribute to the curved anisotropy pattern.The Tibetan Plateau is acted upon by a NE-trending force due to the subduction of the Indian Plate,and also affected by a westward drag force due to the westward retreat produced by the eastward subduction of the Burma slab.The two forces contribute to a curved lithospheric deformation that results in the alignment of the upper mantle peridotite lattice parallel to the deformation direction,and thus generates a curved pattern of fast directions around the EHS.展开更多
The Southwest Mountainous region of the eastern Himalayas is a hotspot with extraordinarily high biodiversity and endemism, but the processes that have driven this unique diversity are largely unknown. We evaluated pr...The Southwest Mountainous region of the eastern Himalayas is a hotspot with extraordinarily high biodiversity and endemism, but the processes that have driven this unique diversity are largely unknown. We evaluated processes that have con- tributed to the current observed high genetic diversity in this region by integrating comparative phylogeography with ecological niche modeling in a study of two representative birds of the Southwest Mountains： the black-throated bushtit Aegithalos concinnus and the Elliot＇s laughing thrush Garrulax elliotii. Mitochondrial DNA analyses revealed multiple divergent genetic lineages, which are roughly congruent with the north, south and east eco-subregion division of the Southwest Mountains. This strong geo- graphical structure in these two species suggests that lineage diversification has proceeded in situ between the eco-subregions of the Southwest Mountains. During Pleistocene glaciations, the two species responded differently to climatic fluctuations. A. con- cinnus maintained rather stable habitats, mostly evergreen forests, during glacial cycles and thus kept a stable population size and further accumulated genetic diversity. In contrast, G. elliotii, which is mostly active in shrublands, has shifted its suitable habitats with glacial cycles. This species dispersed to low elevation areas during glacial periods, which provided multiple opportunities for gene admixture. The admixture causes the mixing of previously isolated genetic lineages and thus obscures the pattern of genetic variation [Current Zoology 61 （5）： 935-942, 2015].展开更多
基金supported by the Special Fund for Meteorological Research in the Public Interest (GYHY2012 06041)the National Natural Science Foundation of China (Grant No.40905067)and the Ministry of Science and Technology of the People’s Republic of China (2009CB421403)
文摘Previous studies have shown that reanalysis products contain large uncertainties in the Tibetan Plateau(TP),and the biases are location dependent.Therefore,these products must be evaluated with in situ observations prior to their applications.In this study,the authors compare the results of several reanalysis projects with independent sounding observations recorded in the Yarlung Tsangpo River valley in the Eastern Himalayas in June 2010.These reanalysis projects include Climate Forecast System Reanalysis(CFSR),Interim European Centre for Medium Range Weather Forecasts Reanalysis(ERA- Interim),Japanese 25-year Reanalysis(JRA-25),Modern Era Retrospective Analysis for Research and Applications(MERRA),National Center for Environmental Prediction and the Department of Energy Reanalysis 2(NCEP-R2),and NCEP Final Analysis(FNL).Statistical quantities such as average,mean bias(MB),root-mean-square difference(RMSD),and correlation coefficient(R) of temperature,specific humidity,u-wind,and v-wind between 100 hPa and 650 hPa were calculated.The authors determined that the performance of each product differed with variables at different levels.The average profiles of the variables were captured by the reanalysis products,with large biases appearing at lower levels.ERA-Interim and NCEP-R2 showed the best and worst performances,respectively,for all variables.This study suggests that users should select appropriate reanalysis products according to their specific purposes for TP research.
基金University Grants Commission(UGC),Nepal for providing financial support。
文摘This study investigates the spatial and temporal variation of fractal dimension and b-value for the eastern part of the Himalaya and adjoining area(26°N–31°N and 87°E–98°E).The analysis is carried out on the earthquake dataset of 1373 events(Mc=4.0)by sliding window technique for the period 1964 to 2020.The region is divided into three sub regions A(87°E–92°E),B(92°E–94°E)and C(94°E–98°E).The b-value computed for the region A comprising eastern Nepal is smaller compared to other two regions which infers the possible high stress and asperities in the region.High spatial fractal dimension(Dc>1.5)and low temporal fractal dimension(Dt<0.31)are computed for the regions.High spatial fractal dimension may indicate that fractures generating earthquakes are approaching a 2D structure and low temporal fractal dimension implies high clustering of earthquake’s epicenters.The b value shows a weak negative correlation with Dc for regions A and C while a weak positive correlation is observed for the region B.Based on b-value and fractal dimension,this study explains the frequency of earthquakes and heterogeneity of the seismogenic structure in this part of the Himalaya.
基金supported by National Natural Science Foundation of China for Young Foundation (Grant No. 40802050)China Postdoctoral Science Foundation (Grant No. 20070420065)
文摘Here we describe ductile, ductile-brittle and brittle deformation styles in the northern segment of the Tertiary Biluoxue- shan-Chongshan shear zone lying to the east of the Eastern Himalayan Syntaxis. In the northernmost part of the zone in the vi- cinity of the Eastern Himalayan Syntaxis, it consists of mylonitic gneiss, granite, and schist. Based on field relations and min- eral assemblages, the rocks are classified into gneiss belt in the west limb, including banded gneiss, augen mylonite and mig- matite gneiss, and schist belt in the east limb. Except for the massive granite pluton, the other three tectonites are affected by polystage deformation （D1-D4）. Fold deformation of the first stage D1 is isoclinal to tight pattern with nearly N-S fold axes and steeply axial planar cleavage S 1, which resulted in the local crustal thickening under a contractive setting. D2 overprinted D1 and is characterized by tight folds with steep axes and N-S fold axial planar, which are also characterized by large-scale ductile strike-slip shear foliation $2, parallel to the nearly N-S trending axial planes of D1 and D2. The structural pattern of D2 represents a transpression along the zone. D3 occurred during the late stage of the transpression or post-transpression, produc- ing the NW-SE and NE-SW trending strike-slip faults of the third stage D3. Following the D3 deformation, the zone was ex- humed to shallow crustal level where the various tectonites underwent a brittle transtensional deformation D4, combined with one N-S trending strike-slip component and one normal faulting component. Structures and previous geochronologies pre- sented in the paper suggest that the study area is correlated with those in the adjacent tectonic zones, Ailaoshan-Red River shear zone and Gaoligong shear zone in the western Yunnan. It underwent intensive polyphase deformation, namely, crustal thickening, transpression, and transtension, responding to syn-collision and post-collision of India-Eurasia from 65 Ma to cur- rent period east of the Eastern Himalayan Syntaxis.
基金supported by the National Natural Science Foundation of China(Grant Nos.41174070,41474088,41274063)China National Special Fund for Earthquake Scientific Research in Public Interest(Grant Nos.201308011,201008001)the Scientific Investigation of the April 14,2010 M7.1 Yushu,Qinghai Earthquake
文摘Polarization analysis of teleseismic data has been used to determine the XKS(SKS,SKKS,and PKS)fast polarization directions and delay times between fast and slow shear waves for 59 seismic stations of both temporary and permanent broadband seismograph networks deployed in the eastern Himalayan syntaxis(EHS)and surrounding regions.The analysis employed both the grid searching method of the minimum tangential energy and stacking analysis methods to develop an image of upper mantle anisotropy in the EHS and surrounding regions using the newly obtained shear wave splitting parameters and previously published results.The fast polarization directions are oriented along a NE-SW azimuth in the EHS.However,within the surrounding regions,the fast directions show a clockwise rotation pattern around the EHS from NE-SW,to E-W,to NW-SE,and then to N-S.In the EHS and surrounding regions,the fast directions of seismic anisotropy determined using shear wave splitting analysis correlate with surficial geological features including major sutures and faults and with the surface deformation fields derived from global positioning system(GPS)data.The coincidence between structural features in the crust,surface deformation fields and mantle anisotropy suggests that the deformation in the crust and lithospheric mantle is mechanically coupled.In the EHS,the coherence between the fast directions and the NE direction of the subduction of the Indian Plate beneath the Tibetan Plateau suggests that the lithospheric deformation is caused mainly by subduction.In the regions surrounding the EHS,we speculate that a westward retreat of the Burma slab could contribute to the curved anisotropy pattern.The Tibetan Plateau is acted upon by a NE-trending force due to the subduction of the Indian Plate,and also affected by a westward drag force due to the westward retreat produced by the eastward subduction of the Burma slab.The two forces contribute to a curved lithospheric deformation that results in the alignment of the upper mantle peridotite lattice parallel to the deformation direction,and thus generates a curved pattern of fast directions around the EHS.
基金We sincerely thank Chuanying Dai for providing mtDNA sequences of the Aegithalos coneinnus. We also thanks Town Peterson for providing the analysis protocol for the ecological niche model, and Robert G. Moyle for the protocol of genetic analyses. This research was supported by grants from the National Science Foundation of China （Nos 31471990, 31172064 to Y.Q. and 31330073, 30925008 to F.L.） and the Ministry of Science and Technology of the People＇s Republic of China （MOST Grant No. 2011FY120200-3）.
文摘The Southwest Mountainous region of the eastern Himalayas is a hotspot with extraordinarily high biodiversity and endemism, but the processes that have driven this unique diversity are largely unknown. We evaluated processes that have con- tributed to the current observed high genetic diversity in this region by integrating comparative phylogeography with ecological niche modeling in a study of two representative birds of the Southwest Mountains： the black-throated bushtit Aegithalos concinnus and the Elliot＇s laughing thrush Garrulax elliotii. Mitochondrial DNA analyses revealed multiple divergent genetic lineages, which are roughly congruent with the north, south and east eco-subregion division of the Southwest Mountains. This strong geo- graphical structure in these two species suggests that lineage diversification has proceeded in situ between the eco-subregions of the Southwest Mountains. During Pleistocene glaciations, the two species responded differently to climatic fluctuations. A. con- cinnus maintained rather stable habitats, mostly evergreen forests, during glacial cycles and thus kept a stable population size and further accumulated genetic diversity. In contrast, G. elliotii, which is mostly active in shrublands, has shifted its suitable habitats with glacial cycles. This species dispersed to low elevation areas during glacial periods, which provided multiple opportunities for gene admixture. The admixture causes the mixing of previously isolated genetic lineages and thus obscures the pattern of genetic variation [Current Zoology 61 （5）： 935-942, 2015].
