Based on the real-time synchronous measurements of the wind velocity,temperature,the PM10 concentration at 16 m and 47 m during a dust storm event,in which Reynolds number Re exceeds 6×106,this study reveals the ...Based on the real-time synchronous measurements of the wind velocity,temperature,the PM10 concentration at 16 m and 47 m during a dust storm event,in which Reynolds number Re exceeds 6×106,this study reveals the existence of the very large scale motions(VLSMs) during the stable stage both in the stream velocity and the temperature field at the two heights,whose streamwise scales reach up to 10 times the thickness of the boundary layer.The streamwise velocity and the PM10 concentration display a similar frequency corresponding to the peaks of their energy spectra,which implies that the VLSMs of streamwise flow have a significant role in dust transportation.In contrast,the salient deviations of the PM10 concentration at 47 m from the Gaussian distribution are revealed,which means that 47 m is not in the dust transportation layer,but is a region where the dust transportation layer and the outer flow intersect each other.Analysis demonstrates that the energy spectra of the PM10 concentrations at 16 m and 47 m display the "-1" scaling law feature,which has the same frequency range(0.001-0.1 Hz) as that of the wind velocity.This provides a new paradigm for the existence of the self-similarity scaling region in turbulent flow.展开更多
On 25 April 2015,an M_w 7.8 earthquake occurred on the Main Himalaya Thrust fault with a dip angle of^7° about77 km northwest of Kathmandu,Nepal.This Nepal Gorkha event is the largest one on the Himalayan thrust ...On 25 April 2015,an M_w 7.8 earthquake occurred on the Main Himalaya Thrust fault with a dip angle of^7° about77 km northwest of Kathmandu,Nepal.This Nepal Gorkha event is the largest one on the Himalayan thrust belt since 1950.Here we use the compressive sensing method in the frequency domain to track the seismic radiation and rupture process of this event using teleseismic P waves recorded by array stations in North America.We also compute the distribution of static shear stress changes on the fault plane from a coseismic slip model.Our results indicate a dominant east-southeastward unilateral rupture process from the epicenter with an average rupture speed of ~3 km s^(-1).Coseismic radiation of this earthquake shows clear frequency-dependent features.The lower frequency(0.05-0.3 Hz) radiation mainly originates from large coseismic slip regions with negative coseismic shear stress changes.In comparison,higher frequency(0.3-0.6 Hz) radiation appears to be from the down-dip part around the margin of large slip areas,which has been loaded and presents positive coseismic shear stress changes.We propose an asperity model to interpret this Nepal earthquake sequence and compare the frequency-dependent coseismic radiation with that in subduction zones.Such frequency-dependent radiation indicates the depth-varying frictional properties on the plate interface of the Nepal section in the main Himalaya thrust system,similar to previous findings in oceanic subduction zones.Our findings provide further evidence of the spatial correlation between changes of static stress status on the fault plane and the observed frequency-dependent coseismic radiation during large earthquakes.Our results show that the frequency-dependent coseismic radiation is not only found for megathrust earthquakes in the oceanic subduction environment,but also holds true for thrust events in the continental collision zone.展开更多
The combination of field surveys with analysis of microstructure of tectonite and Electron Backscatter Diffraction(EBSD) on quartz fabric indicated that three periods of ductile shear events developed in the Paishanlo...The combination of field surveys with analysis of microstructure of tectonite and Electron Backscatter Diffraction(EBSD) on quartz fabric indicated that three periods of ductile shear events developed in the Paishanlou gold deposits and the E-W and NE-striking ductile shear zones were formed during each event.The E-W-striking ductile shear zone,accompanied by compressional and dextral shear slip,was shear-cut by the NE-striking shear zones,accompanied by compressional-sinistral shear slip and sinistral-normal shear slip,successively.An E-W-striking ductile shear zone developed at a deeper tectonic level and at middle- to high-temperatures,accompanied by abundant microstructures,including microlayering between a polycrystal quartz belt and mica,and quartz deformation was depended on cylinder(10-10) or <c> glide.The development of an E-W-striking shear zone can be seen as a tectonic pattern in the region of the Paishanlou gold deposits of the collision between the Mongolian tectonic belt and the North Archean Craton from Suolun to the Linxi suture zone during the Indosinian.The NE-striking ductile shear zone developed approximately 160 Ma during the early Yianshanian at middle to shallow tectonic levels and at middle- to low-temperatures,accompanied by typical microstructures,including polycrystal quartz aggregation and quartz subgrain rotation recrystallization,etc.,and quartz deformation was depended on prismatic(1011) glide.The last ductile shear event around the NE-striking shear zone developed at low temperatures and shallow tectonic levels,yielding to a pre-existing NE-striking shear zone,accompanied by abundant microstructures,including low-temperature quartz grain boundary migration and bulging recrystallization.The last ductile shear movement may be related to lithosphere thinning and the destruction of the North China Craton from approximately 130-120 Ma,and this shear event resulted directly in the mineralization in the Paishanlou region.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 11232006,11121202,10972164,40830103,and 11072097)the State Key Dvelopment Program for Basic Research of China (Grant No. 2009CB421304)
文摘Based on the real-time synchronous measurements of the wind velocity,temperature,the PM10 concentration at 16 m and 47 m during a dust storm event,in which Reynolds number Re exceeds 6×106,this study reveals the existence of the very large scale motions(VLSMs) during the stable stage both in the stream velocity and the temperature field at the two heights,whose streamwise scales reach up to 10 times the thickness of the boundary layer.The streamwise velocity and the PM10 concentration display a similar frequency corresponding to the peaks of their energy spectra,which implies that the VLSMs of streamwise flow have a significant role in dust transportation.In contrast,the salient deviations of the PM10 concentration at 47 m from the Gaussian distribution are revealed,which means that 47 m is not in the dust transportation layer,but is a region where the dust transportation layer and the outer flow intersect each other.Analysis demonstrates that the energy spectra of the PM10 concentrations at 16 m and 47 m display the "-1" scaling law feature,which has the same frequency range(0.001-0.1 Hz) as that of the wind velocity.This provides a new paradigm for the existence of the self-similarity scaling region in turbulent flow.
基金supported by National Natural Science Foundation of China(Grant Nos.41374055,41225010)Chinese University of Hong Kong Direct Grant for Research(Grant No. 3132771)+1 种基金HKSAR Research Grant Council ECS(Grant No.2191093) and GRF(Grant No.2130509)the Fundamental Research Funds for the Central Universities(Grant No.WK2080000053)
文摘On 25 April 2015,an M_w 7.8 earthquake occurred on the Main Himalaya Thrust fault with a dip angle of^7° about77 km northwest of Kathmandu,Nepal.This Nepal Gorkha event is the largest one on the Himalayan thrust belt since 1950.Here we use the compressive sensing method in the frequency domain to track the seismic radiation and rupture process of this event using teleseismic P waves recorded by array stations in North America.We also compute the distribution of static shear stress changes on the fault plane from a coseismic slip model.Our results indicate a dominant east-southeastward unilateral rupture process from the epicenter with an average rupture speed of ~3 km s^(-1).Coseismic radiation of this earthquake shows clear frequency-dependent features.The lower frequency(0.05-0.3 Hz) radiation mainly originates from large coseismic slip regions with negative coseismic shear stress changes.In comparison,higher frequency(0.3-0.6 Hz) radiation appears to be from the down-dip part around the margin of large slip areas,which has been loaded and presents positive coseismic shear stress changes.We propose an asperity model to interpret this Nepal earthquake sequence and compare the frequency-dependent coseismic radiation with that in subduction zones.Such frequency-dependent radiation indicates the depth-varying frictional properties on the plate interface of the Nepal section in the main Himalaya thrust system,similar to previous findings in oceanic subduction zones.Our findings provide further evidence of the spatial correlation between changes of static stress status on the fault plane and the observed frequency-dependent coseismic radiation during large earthquakes.Our results show that the frequency-dependent coseismic radiation is not only found for megathrust earthquakes in the oceanic subduction environment,but also holds true for thrust events in the continental collision zone.
基金supported by National Crisis Mine Program(Grant No.20089931)National Natural Science Foundation of China(Grant Nos.90814006,91214301,41172089)Foundation of Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Minerals(Grant No.DMSM201005)
文摘The combination of field surveys with analysis of microstructure of tectonite and Electron Backscatter Diffraction(EBSD) on quartz fabric indicated that three periods of ductile shear events developed in the Paishanlou gold deposits and the E-W and NE-striking ductile shear zones were formed during each event.The E-W-striking ductile shear zone,accompanied by compressional and dextral shear slip,was shear-cut by the NE-striking shear zones,accompanied by compressional-sinistral shear slip and sinistral-normal shear slip,successively.An E-W-striking ductile shear zone developed at a deeper tectonic level and at middle- to high-temperatures,accompanied by abundant microstructures,including microlayering between a polycrystal quartz belt and mica,and quartz deformation was depended on cylinder(10-10) or <c> glide.The development of an E-W-striking shear zone can be seen as a tectonic pattern in the region of the Paishanlou gold deposits of the collision between the Mongolian tectonic belt and the North Archean Craton from Suolun to the Linxi suture zone during the Indosinian.The NE-striking ductile shear zone developed approximately 160 Ma during the early Yianshanian at middle to shallow tectonic levels and at middle- to low-temperatures,accompanied by typical microstructures,including polycrystal quartz aggregation and quartz subgrain rotation recrystallization,etc.,and quartz deformation was depended on prismatic(1011) glide.The last ductile shear event around the NE-striking shear zone developed at low temperatures and shallow tectonic levels,yielding to a pre-existing NE-striking shear zone,accompanied by abundant microstructures,including low-temperature quartz grain boundary migration and bulging recrystallization.The last ductile shear movement may be related to lithosphere thinning and the destruction of the North China Craton from approximately 130-120 Ma,and this shear event resulted directly in the mineralization in the Paishanlou region.
