Through sampling in farmland and analysis in laboratory,the contents and the pollution level of Cr,Cu,As,Pb,Zn in different soils were studied. The comparative result showed that the As in all soil samples are lower t...Through sampling in farmland and analysis in laboratory,the contents and the pollution level of Cr,Cu,As,Pb,Zn in different soils were studied. The comparative result showed that the As in all soil samples are lower than the mean value of Shaanxi and whole nation,the Cr in lower half soil samples are higher than the mean value of Shaanxi and whole nation,the Cu and Zn in majority soil samples are higher than the mean value of Shaanxi and whole nation,and the Pb in all soil samples is higher than the mean value of Shaanxi and whole nation. The single factor pollution index and multi-factor pollution index method were used to evaluate the soil pollution. According to Soil Environmental Quality Standard,the studied soils were at unpolluted degrees,the soils were clear,the quality of soil adapt to the crop growth,and not affect the quality of agricultural product.展开更多
The Taihang Mountain piedmont fault is a large-scale structure zone in north and east China which cross Beijing,with the NE-NNE extent spans approximately 620 km.It is very important to determine the fault zone activi...The Taihang Mountain piedmont fault is a large-scale structure zone in north and east China which cross Beijing,with the NE-NNE extent spans approximately 620 km.It is very important to determine the fault zone activity due to the close relation of active structures and earthquakes.Regarding the fault activity,there are three different opinions:1) it is a large deep fault zone;2) it is an active fault zone and an earthquake structure belt;and 3) it is not an earthquake structure belt.In order to ascertain the active character of the fault,the deep tectonic setting and the activity since the Quaternary were investigated using recent seismic and drilling data to make a joint interpretation.The investigation results show that the Taihang Mountain piedmont fault is not a large lithospheric fault because the early middle Pleistocene(Q(P2)) layers are offset by the fault and the late middle Pleistocene(Q(P2)) and late Pleistocene layers are not offset by the fault.We determine that the Taihang Mountain piedmont fault in the area is not an active fault and is also not a large lithospheric fault.This study result provides important geological and geophysical data for city planning and construction in Hebei province and, especially,has great significance for seismic hazard assessment of the capital area.展开更多
Windthrow plays a critical role in maintaining species diversity in temperate forests. Do large-scale strong wind events(i.e., tropical cyclones, including hurricanes,typhoons and severe cyclonic storms) increase tree...Windthrow plays a critical role in maintaining species diversity in temperate forests. Do large-scale strong wind events(i.e., tropical cyclones, including hurricanes,typhoons and severe cyclonic storms) increase tree diversity in severely damaged forest areas? Do hurricanes(tropical cyclones that occurs in the Atlantic Ocean and northeastern Pacific Ocean) lead to altered relative abundance of shade-tolerant and shade-intolerant species? Did historic hurricanes alter the succession trajectory of the damaged forests? We used nearly 70-year tree demographic data to assess the effects of two major hurricanes on woody species diversity in Piedmont forests, North Carolina, USA. Species richness(S) and Shannon–Wiener's diversity index(H') were used to evaluate the changes in tree diversity. The changes in composition were assessed with Nonmetric Multidimensional Scaling. The pre-hurricane successional phase can strongly influence both the damage severity and subsequent responses. Although there is often an immediate drop in diversity following a hurricane, understory tree diversity quickly increases to levels that exceed those prior to the disturbance. This leads to an increase in diversity in stands that were substantially damaged. Hurricanes significantly decrease the dominance of shade-intolerant canopy species while increasing preestablished, more shade-tolerant species. We conclude that large, and infrequent hurricanes help to maintain local tree diversity, but also accelerate the increase in dominance of understory species such as red maple and beech.展开更多
Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault (LSPF), one of the most active faults in the Hetao fault zone in Inner Mongol...Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault (LSPF), one of the most active faults in the Hetao fault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic ^10Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 Ira and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 ±0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches.展开更多
The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and...The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and has been highly active since the Cenozoic. The well–known Great Huaxian County Earthquake of 1556 occurred on the Huashan piedmont fault. This earthquake, which claimed the lives of approximately 830000 people, is one of the few large earthquakes known to have occurred on a high–angle normal fault. The Huashan piedmont fault is a typical active normal fault that can be used to study tectonic activity and the associated hazards. In this study, the types and characteristics of late Quaternary deformation along this fault are discussed from geological investigations, historical research and comprehensive analysis. On the basis of its characteristics and activity, the fault can be divided into three sections, namely eastern, central and western. The eastern and western sections display normal slip. Intense deformation has occurred along the two sections during the Quaternary; however, no deformation has occurred during the Holocene. The central section has experienced significant high–angle normal fault activity during the Quaternary, including the Holocene. Holocene alluvial fans and loess cut by the fault have been identified at the mouths of many stream valleys of the Huashan Mountains along the central section of the Huashan piedmont fault zone. Of the three sections of the Huashan piedmont fault, the central section is the most active and was very active during the late Quaternary. The rate of normal dip–slip was 1.67–2.71±0.11 mm/a in the Holocene and 0.61±0.15 mm/a during the Mid–Late Pleistocene. As is typical of normal faults, the late Quaternary activity of the Huashan piedmont fault has produced a set of disasters, which include frequent earthquakes, collapses, landslides, mudslides and ground fissures. Ground fissures mainly occur on the hanging–wall of the Huashan piedmont fault, with landslides, collapses and mudslides occurring on the footwall.展开更多
After the middle of 1960s,along with the appearance and extensive utilization of computer featured in large capacity and rapid speed,numerical method(mainly include finite difference method and finite element
Three Envisat images from ESA were used to derive the pre - and co-seismic deformation interfereograms caused by the Damxung Ms6. 6 earthquake of Oct. 6,2008 ,by using InSAR. The result shows no significant crustal mo...Three Envisat images from ESA were used to derive the pre - and co-seismic deformation interfereograms caused by the Damxung Ms6. 6 earthquake of Oct. 6,2008 ,by using InSAR. The result shows no significant crustal motion more than 4 months before the earthquake, but a maximum co-seismic displacement of about 0.3 m in an epicentral area of 20 km × 20 km. The deformation field was symmetrically distributed about a NS axis, where the west side subsided and the east side uplifted. We used a linear elastic dislocation model in half space and a nonlinear constraint optimized algorithm to estimate the slip distribution along the fault. The results indicates that the epicenter is located at 90. 374°E ,29. 745°N with a moment magnitude of Mw6. 35. The earthquake is dominated by normal faulting with a maximum slip of 3 m on a 12 km × 11 km fault plane striking S189°W,dipping 60° to NW at a depth of 9.5 km,and is located at a sub-fault of the southeastern Piedmont of the Nyainqentanglha mountains. The relatively shallow depth of earthquake is related to relatively high heat flow in the area.展开更多
Horizontal soil column method was used to determine the horizontal diffusion rate of sandy loam, loam and clay loam under the same bulk density. The results showed that the migration rates of different lithological we...Horizontal soil column method was used to determine the horizontal diffusion rate of sandy loam, loam and clay loam under the same bulk density. The results showed that the migration rates of different lithological wet fronts were different. The sandy loam had the fastest migration rate, the loam followed, and the clay loam was the slowest, but the law of change is the same among the three lithologies. The volumetric water content affects the change of Boltzmann parameter λ. When the volumetric water content is between 0.35-0.45 cm^3/cm^3,λ approaches stability. When the volumetric water content is less than 0.35 cm^3/cm^3, the λ value decreases rapidly with the decrease of water content. The water diffusion rate is related to the volumetric water content and particle size. The greater the moisture content is, the greater the diffusion rate will be. The larger the particle size, the larger the diffusion rate. The diffusivity of sandy loam is 10-30 times larger than that of loam and clay loam. The relationship between water content and diffusion rate is in accordance with the exponential function .展开更多
This study analyses thirteen daily precipitation series of Piedmont, region of North-West Italy. The meteorological series have been chosen because they were meteorological observatories operating continuously from th...This study analyses thirteen daily precipitation series of Piedmont, region of North-West Italy. The meteorological series have been chosen because they were meteorological observatories operating continuously from the beginning of 1900 until 2011. As the first step an historical research over each station has been carried out. In this way, the potential breaks, in the series, either due to changes of locations or instruments, have been determined and the missing values have been recovered. On the precipitation daily series a quality control have been effectuated and by metadata identification it was possible to assess the homogeneity of the meteorological series. In this way we have obtained the complete and correct series on which trends have been computed. In order to better understand the consequences of climate variations on our environment and society, we have calculated the climate indices proposed by “CCL/CLIVAR Working Group on Climate Change Detection” (dry and wet days, rainy days, intensity of precipitation…) over the time. The values of precipitation have also allowed beginning the climatic analysis with the aim at defining the principle local peculiarity in Piedmont.展开更多
A detailed study on geomorphic surfaces and a set of trenches on the Hohhot segment of Daqingshan piedmont fault at three sites, Kuisu, Ulan Blang, and Qingshan Grassland, revealed 7 paleoseismic events occurred along...A detailed study on geomorphic surfaces and a set of trenches on the Hohhot segment of Daqingshan piedmont fault at three sites, Kuisu, Ulan Blang, and Qingshan Grassland, revealed 7 paleoseismic events occurred along the fault segment since 19 ka BP. Those events occurred at 18.75±.75 ka, 16.97 ±.96 ka, 14.65±.67 ka, 11.82±.69 ka, 9.45±.26 ka, 6. 83±.26 ka, and 4. 50 ±0. 23 ka BP, respectively, and their average recurrence interval is 2375±432 years. From the results of constraining fault displacement and correlation between the sediments in these trenches, we found a complete paleoseismic activity history along the fault segment during this period of time.展开更多
Geomorphic study on Wujiahe segment of Serteng piedmont fault, Inner Mongolia is made. Through analysis of the available data in combination with the results of predecessors studies it can be obtained that average ver...Geomorphic study on Wujiahe segment of Serteng piedmont fault, Inner Mongolia is made. Through analysis of the available data in combination with the results of predecessors studies it can be obtained that average vertical displacement rate is 0.48~0.75 mm/a along the Wujiahe segment since the late Pleistocene (14.450~22.340 ka BP) and 0.56~0.88 mm/a since the early-middle Holocene (5.570~8.830 ka BP). Analyzing paleoseismic phenomena revealed in the excavated 5 trenches in combination with the results of predecessors studies of paleoearthquakes on the fault, we determine five paleoseismic events on the Wujiahe segment of Serteng piedmont fault since 27.0 ka BP and the recurrence interval to be about 4.300~4.400 ka. A cluster of paleoearthquakes occurred probably during 8.000~9.000 ka BP and two paleoseismic events in 10.000~20.000 ka BP may be missed. A comparison between height of fault scarps and sum of displacement caused by paleoseismic events revealed in trenches, and recurrence interval of paleoseismic events obtained from average displacement rate along the fault and the disloca-tion by one event suggest that three paleoseismic events are absent in Alagaitu trench. Two paleoseismic events may be absent on the whole active fault segment.展开更多
Fire is a natural disturbance occurring every few years in many grasslands ecosystems. However, since European colonization, fire has been highly reduced or even suppressed in Argentinean grasslands, fostering ignitab...Fire is a natural disturbance occurring every few years in many grasslands ecosystems. However, since European colonization, fire has been highly reduced or even suppressed in Argentinean grasslands, fostering ignitable material accumulation. This has led to occasional catastrophic controldemanding fire events, extended for larger areas. The aims of this work are to study vegetation recovery and change after a non-natural fire event in mountain grasslands. The study area is located in the Ventania mountain system, mid-eastern Argentina. We studied vegetation recovery after fire(January 2014) in two different communities: grass-steppes(grasslands) and shrub-steppes(open low shrublands). We measured vegetation cover, species richness and bare ground percentage in burned and unburned areas 1, 4, 8, 11 and 23 months after fire. Vegetation surveys were also performed at the end of the growing season(December) 11 and 23 months after fire. Data were analyzed using regression analysis, ANOVA and multivariate analysis(NMS, PERMANOVA). Both communities increased their vegetation cover at the same rate, without differences between burned and unburned areas after two years. Species richness was higher in shrublands and their recovery was alsofaster than in grasslands. Considering functional composition, besides transient changes during the first year after fire, there were no differences in abundance of different functional vegetation groups two years after fire. At the same time, shrublands showed no differences in species composition, while grasslands had a different species composition in burned and unburned plots. Also, burned grassland showed a higher species richness than unburned grassland. Data shown mountain vegetation in Pampas grassland is adapted to fire, recovering cover and richness rapidly after fire and thus reducing soil erosion risks. Vegetation in mountain Pampas seems to be well adapted to fire, but in grasslands species composition has changed due to fire. Nonetheless, these changes seem to be not permanent since prefire species are still present in the area.展开更多
According to volume 18(Xuanzong Ji Tang)of the historical book entitled the Old Book of Tang,the Hetao area of Inner Mongolia experienced a large earthquake in AD 849.However,previous work on that earthquake contains ...According to volume 18(Xuanzong Ji Tang)of the historical book entitled the Old Book of Tang,the Hetao area of Inner Mongolia experienced a large earthquake in AD 849.However,previous work on that earthquake contains many discrepancies regarding its epicenter location,magnitude,deaths,and intensity.While exploring active faults in Baotou City,the present authors mapped the Daqing Mountain piedmont fault geologically.Based on previous work,several seismic deformation traces of more than 1000 years ago were found,and dating tests were conducted.The research showed the Daqing Mountain piedmont fault zone to be the seismogenic structure of the AD 849 earthquake.The length of earthquake surface rupture zone was around 80 km,and the macro epicenter was located in the active fault.The deformation center was located at 40.6°N,110.2°E.By collecting and analyzing more historical data about the AD 849 earthquake,reinterpreting some existing historical data,and re-examining the contradictory numbers of deaths in the historical data,the present analysis concludes that around 10,000 people were dead.It is suggested that this earthquake had a magnitude of 7½.According to the revised seismic parameters and the paleoearthquake recurrence period of the Daqing Mountain piedmont fault,the boundary of some potential seismic sources zone in the Baotou area are adjusted and the recurrence period of M8 and M7.5 are re-calculated.展开更多
基金Supported by National Natural Science Foundation of China(40772160)~~
文摘Through sampling in farmland and analysis in laboratory,the contents and the pollution level of Cr,Cu,As,Pb,Zn in different soils were studied. The comparative result showed that the As in all soil samples are lower than the mean value of Shaanxi and whole nation,the Cr in lower half soil samples are higher than the mean value of Shaanxi and whole nation,the Cu and Zn in majority soil samples are higher than the mean value of Shaanxi and whole nation,and the Pb in all soil samples is higher than the mean value of Shaanxi and whole nation. The single factor pollution index and multi-factor pollution index method were used to evaluate the soil pollution. According to Soil Environmental Quality Standard,the studied soils were at unpolluted degrees,the soils were clear,the quality of soil adapt to the crop growth,and not affect the quality of agricultural product.
基金supported by the Fund Project:Subsidized by the Project of City Active Fault Detection and Seismic Risk Assessment in Hebei Province(Handan City).
文摘The Taihang Mountain piedmont fault is a large-scale structure zone in north and east China which cross Beijing,with the NE-NNE extent spans approximately 620 km.It is very important to determine the fault zone activity due to the close relation of active structures and earthquakes.Regarding the fault activity,there are three different opinions:1) it is a large deep fault zone;2) it is an active fault zone and an earthquake structure belt;and 3) it is not an earthquake structure belt.In order to ascertain the active character of the fault,the deep tectonic setting and the activity since the Quaternary were investigated using recent seismic and drilling data to make a joint interpretation.The investigation results show that the Taihang Mountain piedmont fault is not a large lithospheric fault because the early middle Pleistocene(Q(P2)) layers are offset by the fault and the late middle Pleistocene(Q(P2)) and late Pleistocene layers are not offset by the fault.We determine that the Taihang Mountain piedmont fault in the area is not an active fault and is also not a large lithospheric fault.This study result provides important geological and geophysical data for city planning and construction in Hebei province and, especially,has great significance for seismic hazard assessment of the capital area.
基金supported by a grant from the National Science Foundation(DEB-97-07551)
文摘Windthrow plays a critical role in maintaining species diversity in temperate forests. Do large-scale strong wind events(i.e., tropical cyclones, including hurricanes,typhoons and severe cyclonic storms) increase tree diversity in severely damaged forest areas? Do hurricanes(tropical cyclones that occurs in the Atlantic Ocean and northeastern Pacific Ocean) lead to altered relative abundance of shade-tolerant and shade-intolerant species? Did historic hurricanes alter the succession trajectory of the damaged forests? We used nearly 70-year tree demographic data to assess the effects of two major hurricanes on woody species diversity in Piedmont forests, North Carolina, USA. Species richness(S) and Shannon–Wiener's diversity index(H') were used to evaluate the changes in tree diversity. The changes in composition were assessed with Nonmetric Multidimensional Scaling. The pre-hurricane successional phase can strongly influence both the damage severity and subsequent responses. Although there is often an immediate drop in diversity following a hurricane, understory tree diversity quickly increases to levels that exceed those prior to the disturbance. This leads to an increase in diversity in stands that were substantially damaged. Hurricanes significantly decrease the dominance of shade-intolerant canopy species while increasing preestablished, more shade-tolerant species. We conclude that large, and infrequent hurricanes help to maintain local tree diversity, but also accelerate the increase in dominance of understory species such as red maple and beech.
基金supported by the National Natural Science Foundation of China (Grant No.41171001)the 1:50000 Active Fault Mapping of Langshan Piedmont Fault (Grant No.201408023)the Basic Research Business Foundation of the China Earthquake Administration (Grant No.ZDJ2012-02)
文摘Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault (LSPF), one of the most active faults in the Hetao fault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic ^10Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 Ira and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 ±0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches.
基金granted by the Geological Investigation Project of China Geological Survey (Grant Nos.1212011120102 and 12120115003501)
文摘The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and has been highly active since the Cenozoic. The well–known Great Huaxian County Earthquake of 1556 occurred on the Huashan piedmont fault. This earthquake, which claimed the lives of approximately 830000 people, is one of the few large earthquakes known to have occurred on a high–angle normal fault. The Huashan piedmont fault is a typical active normal fault that can be used to study tectonic activity and the associated hazards. In this study, the types and characteristics of late Quaternary deformation along this fault are discussed from geological investigations, historical research and comprehensive analysis. On the basis of its characteristics and activity, the fault can be divided into three sections, namely eastern, central and western. The eastern and western sections display normal slip. Intense deformation has occurred along the two sections during the Quaternary; however, no deformation has occurred during the Holocene. The central section has experienced significant high–angle normal fault activity during the Quaternary, including the Holocene. Holocene alluvial fans and loess cut by the fault have been identified at the mouths of many stream valleys of the Huashan Mountains along the central section of the Huashan piedmont fault zone. Of the three sections of the Huashan piedmont fault, the central section is the most active and was very active during the late Quaternary. The rate of normal dip–slip was 1.67–2.71±0.11 mm/a in the Holocene and 0.61±0.15 mm/a during the Mid–Late Pleistocene. As is typical of normal faults, the late Quaternary activity of the Huashan piedmont fault has produced a set of disasters, which include frequent earthquakes, collapses, landslides, mudslides and ground fissures. Ground fissures mainly occur on the hanging–wall of the Huashan piedmont fault, with landslides, collapses and mudslides occurring on the footwall.
基金sponsored by National key basic research development plan (973) theme ( No. 2011CB403003 )CUG investigation project ( No. 1212011220789 )
文摘After the middle of 1960s,along with the appearance and extensive utilization of computer featured in large capacity and rapid speed,numerical method(mainly include finite difference method and finite element
基金supported by the National Natural Science Fundation of China(40774014,40674054,40575011,40674009)
文摘Three Envisat images from ESA were used to derive the pre - and co-seismic deformation interfereograms caused by the Damxung Ms6. 6 earthquake of Oct. 6,2008 ,by using InSAR. The result shows no significant crustal motion more than 4 months before the earthquake, but a maximum co-seismic displacement of about 0.3 m in an epicentral area of 20 km × 20 km. The deformation field was symmetrically distributed about a NS axis, where the west side subsided and the east side uplifted. We used a linear elastic dislocation model in half space and a nonlinear constraint optimized algorithm to estimate the slip distribution along the fault. The results indicates that the epicenter is located at 90. 374°E ,29. 745°N with a moment magnitude of Mw6. 35. The earthquake is dominated by normal faulting with a maximum slip of 3 m on a 12 km × 11 km fault plane striking S189°W,dipping 60° to NW at a depth of 9.5 km,and is located at a sub-fault of the southeastern Piedmont of the Nyainqentanglha mountains. The relatively shallow depth of earthquake is related to relatively high heat flow in the area.
基金financially supported by the Fundamental Research Fund of the Chinese Academy of Geological Sciences (YYFM201624)
文摘Horizontal soil column method was used to determine the horizontal diffusion rate of sandy loam, loam and clay loam under the same bulk density. The results showed that the migration rates of different lithological wet fronts were different. The sandy loam had the fastest migration rate, the loam followed, and the clay loam was the slowest, but the law of change is the same among the three lithologies. The volumetric water content affects the change of Boltzmann parameter λ. When the volumetric water content is between 0.35-0.45 cm^3/cm^3,λ approaches stability. When the volumetric water content is less than 0.35 cm^3/cm^3, the λ value decreases rapidly with the decrease of water content. The water diffusion rate is related to the volumetric water content and particle size. The greater the moisture content is, the greater the diffusion rate will be. The larger the particle size, the larger the diffusion rate. The diffusivity of sandy loam is 10-30 times larger than that of loam and clay loam. The relationship between water content and diffusion rate is in accordance with the exponential function .
文摘This study analyses thirteen daily precipitation series of Piedmont, region of North-West Italy. The meteorological series have been chosen because they were meteorological observatories operating continuously from the beginning of 1900 until 2011. As the first step an historical research over each station has been carried out. In this way, the potential breaks, in the series, either due to changes of locations or instruments, have been determined and the missing values have been recovered. On the precipitation daily series a quality control have been effectuated and by metadata identification it was possible to assess the homogeneity of the meteorological series. In this way we have obtained the complete and correct series on which trends have been computed. In order to better understand the consequences of climate variations on our environment and society, we have calculated the climate indices proposed by “CCL/CLIVAR Working Group on Climate Change Detection” (dry and wet days, rainy days, intensity of precipitation…) over the time. The values of precipitation have also allowed beginning the climatic analysis with the aim at defining the principle local peculiarity in Piedmont.
基金The research as one of the key project was supported by Joint Seismological Science Foundation grant 95-07-421. Contribution No. 2001 B001, Institute of Geology, China Seismological Bureau, China.
文摘A detailed study on geomorphic surfaces and a set of trenches on the Hohhot segment of Daqingshan piedmont fault at three sites, Kuisu, Ulan Blang, and Qingshan Grassland, revealed 7 paleoseismic events occurred along the fault segment since 19 ka BP. Those events occurred at 18.75±.75 ka, 16.97 ±.96 ka, 14.65±.67 ka, 11.82±.69 ka, 9.45±.26 ka, 6. 83±.26 ka, and 4. 50 ±0. 23 ka BP, respectively, and their average recurrence interval is 2375±432 years. From the results of constraining fault displacement and correlation between the sediments in these trenches, we found a complete paleoseismic activity history along the fault segment during this period of time.
基金State Key Basic Research Development and Programming Project Mechanism and Prediction of Continental Strong Earthquakes (G199804070) and Joint Earthquake Science Foundation of China (100068).
文摘Geomorphic study on Wujiahe segment of Serteng piedmont fault, Inner Mongolia is made. Through analysis of the available data in combination with the results of predecessors studies it can be obtained that average vertical displacement rate is 0.48~0.75 mm/a along the Wujiahe segment since the late Pleistocene (14.450~22.340 ka BP) and 0.56~0.88 mm/a since the early-middle Holocene (5.570~8.830 ka BP). Analyzing paleoseismic phenomena revealed in the excavated 5 trenches in combination with the results of predecessors studies of paleoearthquakes on the fault, we determine five paleoseismic events on the Wujiahe segment of Serteng piedmont fault since 27.0 ka BP and the recurrence interval to be about 4.300~4.400 ka. A cluster of paleoearthquakes occurred probably during 8.000~9.000 ka BP and two paleoseismic events in 10.000~20.000 ka BP may be missed. A comparison between height of fault scarps and sum of displacement caused by paleoseismic events revealed in trenches, and recurrence interval of paleoseismic events obtained from average displacement rate along the fault and the disloca-tion by one event suggest that three paleoseismic events are absent in Alagaitu trench. Two paleoseismic events may be absent on the whole active fault segment.
基金supported by the ANPCyT under grant PICT 2014-0865CONICET and Universidad Nacional del Sur from Argentina
文摘Fire is a natural disturbance occurring every few years in many grasslands ecosystems. However, since European colonization, fire has been highly reduced or even suppressed in Argentinean grasslands, fostering ignitable material accumulation. This has led to occasional catastrophic controldemanding fire events, extended for larger areas. The aims of this work are to study vegetation recovery and change after a non-natural fire event in mountain grasslands. The study area is located in the Ventania mountain system, mid-eastern Argentina. We studied vegetation recovery after fire(January 2014) in two different communities: grass-steppes(grasslands) and shrub-steppes(open low shrublands). We measured vegetation cover, species richness and bare ground percentage in burned and unburned areas 1, 4, 8, 11 and 23 months after fire. Vegetation surveys were also performed at the end of the growing season(December) 11 and 23 months after fire. Data were analyzed using regression analysis, ANOVA and multivariate analysis(NMS, PERMANOVA). Both communities increased their vegetation cover at the same rate, without differences between burned and unburned areas after two years. Species richness was higher in shrublands and their recovery was alsofaster than in grasslands. Considering functional composition, besides transient changes during the first year after fire, there were no differences in abundance of different functional vegetation groups two years after fire. At the same time, shrublands showed no differences in species composition, while grasslands had a different species composition in burned and unburned plots. Also, burned grassland showed a higher species richness than unburned grassland. Data shown mountain vegetation in Pampas grassland is adapted to fire, recovering cover and richness rapidly after fire and thus reducing soil erosion risks. Vegetation in mountain Pampas seems to be well adapted to fire, but in grasslands species composition has changed due to fire. Nonetheless, these changes seem to be not permanent since prefire species are still present in the area.
基金supported by a subproject of the strategic leading science and technology project(A)of the Chinese Academy of Sciences(No.XDA20070302)we thank the reviewers and editors for their suggestions and opinions.
文摘According to volume 18(Xuanzong Ji Tang)of the historical book entitled the Old Book of Tang,the Hetao area of Inner Mongolia experienced a large earthquake in AD 849.However,previous work on that earthquake contains many discrepancies regarding its epicenter location,magnitude,deaths,and intensity.While exploring active faults in Baotou City,the present authors mapped the Daqing Mountain piedmont fault geologically.Based on previous work,several seismic deformation traces of more than 1000 years ago were found,and dating tests were conducted.The research showed the Daqing Mountain piedmont fault zone to be the seismogenic structure of the AD 849 earthquake.The length of earthquake surface rupture zone was around 80 km,and the macro epicenter was located in the active fault.The deformation center was located at 40.6°N,110.2°E.By collecting and analyzing more historical data about the AD 849 earthquake,reinterpreting some existing historical data,and re-examining the contradictory numbers of deaths in the historical data,the present analysis concludes that around 10,000 people were dead.It is suggested that this earthquake had a magnitude of 7½.According to the revised seismic parameters and the paleoearthquake recurrence period of the Daqing Mountain piedmont fault,the boundary of some potential seismic sources zone in the Baotou area are adjusted and the recurrence period of M8 and M7.5 are re-calculated.