Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface r...Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.展开更多
With the rapid development of remote sensing technology, it has become a technical means of geological research and geological survey. Remote sensing can realize rapid and large area information extraction and provide...With the rapid development of remote sensing technology, it has become a technical means of geological research and geological survey. Remote sensing can realize rapid and large area information extraction and provide effective method for geological hazard extraction. However, due to regional differences, there are some differences between geological hazard occurrence characteristics and extraction indexes in different regions. This paper takes Linjiang City, Jilin Province as an example to extract geological hazards with multisource data. The results show that the remote sensing method can realize the extraction of debris flow, collapse, landslide and other geological hazards in the study area, and obtain high accuracy.展开更多
The compilation of 1:250,000 vegetation type map in the North-South transitional zone and 1:50,000 vegetation type maps in typical mountainous areas is one of the main tasks of Integrated Scientific Investigation of t...The compilation of 1:250,000 vegetation type map in the North-South transitional zone and 1:50,000 vegetation type maps in typical mountainous areas is one of the main tasks of Integrated Scientific Investigation of the North-South Transitional Zone of China.In the past,vegetation type maps were compiled by a large number of ground field surveys.Although the field survey method is accurate,it is not only time-consuming,but also only covers a small area due to the limitations of physical environment conditions.Remote sensing data can make up for the limitation of field survey because of its full coverage.However,there are still some difficulties and bottlenecks in the extraction of remote sensing information of vegetation types,especially in the automatic extraction.As an example of the compilation of 1:50,000 vegetation type map,this paper explores and studies the remote sensing extraction and mapping methods of vegetation type with medium and large scales based on mountain altitudinal belts of Taibai Mountain,using multi-temporal high resolution remote sensing data,ground survey data,previous vegetation type map and forest survey data.The results show that:1)mountain altitudinal belts can effectively support remote sensing classification and mapping of 1:50,000 vegetation type map in mountain areas.Terrain constraint factors with mountain altitudinal belt information can be generated by mountain altitudinal belts and 1:10,000 Digital Surface Model(DSM)data of Taibai Mountain.Combining the terrain constraint factors with multi-temporal and high-resolution remote sensing data,ground survey data and previous small-scale vegetation type map data,the vegetation types at all levels can be extracted effectively.2)The basic remote sensing interpretation and mapping process for typical mountains is interpretation of vegetation type-groups→interpretation of vegetation formation groups,formations and subformations→interpretation and classification of vegetation types&subtypes,which is a combination method of top-down method and bottom-up method,not the top-down or the bottom-up classification according to the level of mapping units.The results of this study provide a demonstration and scientific basis for the compilation of large and medium scale vegetation type maps.展开更多
Based on the ETM remote sensing images of Guangzhou City in 2014, the spatial distribution results o f three environmental factors including vegetation coverage(NDVI), soil index(vegetation index of bare soil) and sl ...Based on the ETM remote sensing images of Guangzhou City in 2014, the spatial distribution results o f three environmental factors including vegetation coverage(NDVI), soil index(vegetation index of bare soil) and sl ope were obtained. By using comprehensive index method, the normalized environmental factors were weighted and superimposed, and the fi nal evaluation results of ecological environment in Guangzhou City were obtained. The results showed that overall situation of natural ecological environment in Guangzhou was not optimistic, that is, the area of land with bad, moderate, good and superior environment accounted for 59.70%, 35.79%, 4.50% and around 0.01% of total area of land in Guangzhou City respectively. Ecological environment was generally poor in the central urban districts in the south of Guangzhou City, while it was relatively better in the north and northeast. Attaching importance to the constr uction of greenbelts and greenways is an effective way to improve regional environmental quality and natural ecological e nvironment level.展开更多
Ecological water supplement projects have been implemented in many coastal wetlands,influencing saltmarsh vegetation restoration by altering tidal creek development.To clarify the effectiveness of ecological water sup...Ecological water supplement projects have been implemented in many coastal wetlands,influencing saltmarsh vegetation restoration by altering tidal creek development.To clarify the effectiveness of ecological water supplement on tidal creek development and saltmarsh vegetation restoration,time series of high-resolution remote sensing images from2000 to 2021 were used to extract and analyze tidal creeks and saltmarsh vegetation in the Diaokou Estuary Reserve.The results are summarized as follows:(1)All tidal creek indices,except curvature,exhibited a significant linear increase with time,while curvature initially decreased and increased afterwards.The 5-year cumulative ecological water supplement volume was significantly positively correlated(R^(2)>0.7)with all tidal creek indices.(2)During the same period,most landscape pattern metrics of Phragmites australis increased,while those of Tamarix chinensis initially increased and then declined.Although the class area(CA)of Suaeda salsa increased with time,its perimeter-area fractal dimension(PAFRAC)and aggregation index(AI)fluctuated.(3)The CA of P.australis and S.salsa was significantly positively correlated with most tidal creek indices except curvature,while that of T.chinensis showed no significant correlation with any tidal creek index.Moreover,the AI and PAFRAC of P.australis were significantly positively correlated with fractal dimension,frequency/curvature of tidal creeks,respectively,while those of S.salsa and T.chinensis exhibited no significant correlation.In summary,the ecological water supplement project enhanced tidal creek development in coastal wetlands,promoting the restoration of P.australis and S.salsa,while having little impact on the restoration of T.chinensis.展开更多
Rapidly obtaining spatial distribution maps of secondary disasters triggered by strong earthquakes is crucial for understanding the disaster-causing processes in the earthquake hazard chain and formulating effective e...Rapidly obtaining spatial distribution maps of secondary disasters triggered by strong earthquakes is crucial for understanding the disaster-causing processes in the earthquake hazard chain and formulating effective emergency response measures and post-disaster reconstruction plans.On April 3,2024,a M_(W)7.4 earthquake struck offshore east of Hualien,Taiwan,China,which triggered numerous coseismic landslides in bedrock mountain regions and severe soil liquefaction in coastal areas,resulting in significant economic losses.This study utilized postearthquake emergency data from China's high-resolution optical satellite imagery and applied visual interpretation method to establish a partial database of secondary disasters triggered by the 2024 Hualien earthquake.A total of 5348 coseismic landslides were identified,which were primarily distributed along the eastern slopes of the Central Mountain Range watersheds.In high mountain valleys,these landslides mainly manifest as localized bedrock collapses or slope debris flows,causing extensive damage to highways and tourism facilities.Their distribution partially overlaps with the landslide concentration zones triggered by the 1999 Chi-Chi earthquake.Additionally,6040 soil liquefaction events were interpreted,predominantly in the Hualien Port area and the lowland valleys of the Hualien River and concentrated within the IX-intensity zone.Widespread surface subsidence and sand ejections characterized soil liquefaction.Verified against local field investigation data in Taiwan,rapid imaging through post-earthquake remote sensing data can effectively assess the distribution of coseismic landslides and soil liquefaction within high-intensity zones.This study provides efficient and reliable data for earthquake disaster response.Moreover,the results are critical for seismic disaster mitigation in high mountain valleys and coastal lowlands.展开更多
On September 5,2022,a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage an...On September 5,2022,a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage and substantial economic loss.In this study,we established a coseismic landslide database triggered by Luding Ms 6.8 earthquake,which includes 4794 landslides with a total area of 46.79 km^(2).The coseismic landslides primarily consisted of medium and small-sized landslides,characterized by shallow surface sliding.Some exhibited characteristics of high-position initiation resulted in the obstruction or partial obstruction of rivers,leading to the formation of dammed lakes.Our research found that the coseismic landslides were predominantly observed on slopes ranging from 30°to 50°,occurring at between 1000 m and 2500 m,with slope aspects varying from 90°to 180°.Landslides were also highly developed in granitic bodies that had experienced structural fracturing and strong-tomoderate weathering.Coseismic landslides concentrated within a 6 km range on both sides of the Xianshuihe and Daduhe fault zones.The area and number of coseismic landslides exhibited a negative correlation with the distance to fault lines,road networks,and river systems,as they were influenced by fault activity,road excavation,and river erosion.The coseismic landslides were mainly distributed in the southeastern region of the epicenter,exhibiting relatively concentrated patterns within the IX-degree zones such as Moxi Town,Wandong River basin,Detuo Town to Wanggangping Township.Our research findings provide important data on the coseismic landslides triggered by the Luding Ms 6.8 earthquake and reveal the spatial distribution patterns of these landslides.These findings can serve as important references for risk mitigation,reconstruction planning,and regional earthquake disaster research in the earthquake-affected area.展开更多
Geohazard recognition and inventory mapping are absolutely the keys to the establishment of reliable susceptibility and hazard maps. However, it has been challenging to implement geohazards recognition and inventory m...Geohazard recognition and inventory mapping are absolutely the keys to the establishment of reliable susceptibility and hazard maps. However, it has been challenging to implement geohazards recognition and inventory mapping in mountainous areas with complex topography and vegetation cover. Progress in the light detection and ranging(Li DAR) technology provides a new possibility for geohazard recognition in such areas. Specifically, this study aims to evaluate the performances of the Li DAR technology in recognizing geohazard in the mountainous areas of Southwest China through visually analyzing airborne Li DAR DEM derivatives. Quasi-3 D relief image maps are generated based on the sky-view factor(SVF), which makes it feasible to interpret precisely the features of geohazard. A total of 146 geohazards are remotely mapped in the entire 135 km^(2) study area in Danba County, Southwest China, and classified as landslide, rock fall, debris flow based on morphologic characteristics interpreted from SVF visualization maps. Field validation indicate the success rate of Li DAR-derived DEM in recognition and mapping geohazard with higher precision and accuracy. These mapped geohazards lie along both sides of the river, and their spatial distributions are related highly to human engineering activities, such as road excavation and slope cutting. The minimum geohazard that can be recognized in the 0.5 m resolution DEM is about 900 m^(2). Meanwhile, the SVF visualization method is demonstrated to be a great alternative to the classical hillshaded DEM method when it comes to the determination of geomorphological properties of geohazard. Results of this study highlight the importance of Li DAR data for creating complete and accurate geohazard inventories, which can then be used for the production of reliable susceptibility and hazard maps and thus contribute to a better understanding of the movement processes and reducing related losses.展开更多
Wind erosion,or the transportation and deposition of sand into desert dunes and aeolian loess,is one of the most important aeolian activities.The progression of aeolian landforms expands arid and barren landscapes,lea...Wind erosion,or the transportation and deposition of sand into desert dunes and aeolian loess,is one of the most important aeolian activities.The progression of aeolian landforms expands arid and barren landscapes,leading to the degradation of adjacent areas.The Gonghe Basin,as a typical plateau with abundant sand sources,is highly sensitive to changes in the local climate conditions.In order to quantify the spatial-temporal variations in the aeolian landforms in the Gonghe Basin,we conducted field surveys and also analyzed twelve remote sensing(Landsat5 TM and Landsat8 OLI)images that sample the Gonghe Basin from 1989 to 2019.In the Gonghe Basin,we identified aeolian landforms such as climbing dunes on the windward slopes of the foothills,checkerboard dunes in the southeastern part of the basin,flat dunes,parabolic dunes and crescent dunes on the east and west sides of Longyangxia Reservoir,shrubby sandbanks on the valley slope in Shazhuyu,Tanggemu,and Indel,and sandy thickets at the bottom of the valley near the Dalian Sea,the Longyangxia Reservoir,and the tributaries of the Yellow River.From 1989 to 2005,the area of the aeolian regions expanded by 816.7 km2,with an annual conversion rate of 0.05%.From 2015 to 2019,the area of the aeolian regions shrunk by 2411.9 km2,with an annual conversion rate of−0.15%.The number and size of the fixed and semi-fixed dunes(e.g.the shrubby sandbanks on the valley slope and the sandy thickets at the bottom of the valley)were more stable than those of the mobile dunes(e.g.the checkerboard dunes,the flat dunes,the crescent dunes,the parabolic dunes,and the climbing dunes).The fixed and semi-fixed dunes were arranged in an irregular ring shape,and the location of the center of gravity of this ring did not change significantly from 1989 to 2019;in this time,the mobile dunes migrated to the northwest.展开更多
As climate change intensifies,finding an ecological indicator to quickly and accurately reflect the impact on mountain ecosystems is necessary.The low treeline/timberline,highly sensitive to climate variability and ch...As climate change intensifies,finding an ecological indicator to quickly and accurately reflect the impact on mountain ecosystems is necessary.The low treeline/timberline,highly sensitive to climate variability and changes significantly within 5–10years,provides a new way to study the response to regional climate variability.This study explored the distribution and vertical displacement patterns of the low treeline in the Upper Minjiang River of China,using SPOT remote sensing images in 1999 and 2013and long-term positional observations.Using the Geodetector model,the study investigated the dominant climatic factors influencing the low treeline displacement.The results showed that the low treeline was located at 1700–3200 m elevation on sunny slopes(southeast,south,southwest,and west slopes)with slopes over 25°.From 1999 to 2013,the low treeline moved downward by 6 m from 2561±264m to 2555±265 m,along with a warm–humid climate tendency.The downward displacement was greater on slopes over 25°and shady slopes(-20 m and-10 m,respectively)than on slopes≤25°and sunny slopes.Additionally,the downward was greater in the warm and humid Zagunao River Basin(-15 m)compared to the arid valley center(-7 m)and the cold Heishui River Basin(-3 m).Meanwhile,the low treeline displacement correlated negatively with precipitation and relative humidity variations at the significance level of 0.05,with correlation coefficients of-0.572and-0.551,respectively.Variations in relative humidity and temperature significantly affected the spatial differentiation of low treeline displacement with influencing power of 0.246(p=0.036<0.05)and 0.183(p=0.032<0.05),respectively.Thus,the low treeline is a moisture-limited line,and its formation and variation are closely related to regional water–heat balance.The study clarifies the indicative value of the low treeline for climate variability in mountain areas and can provide references for ecological restoration in arid valleys.展开更多
The Geological Map of Colombia 2015 summarizes the superficial geological information of Colombia.It is the final product of a process of integration and generalization of the cartographic information of the existing ...The Geological Map of Colombia 2015 summarizes the superficial geological information of Colombia.It is the final product of a process of integration and generalization of the cartographic information of the existing geological maps published by the Colombian Geological Survey complemented by the interpretation of remote sensing imagery of previously unmapped areas.Harmonization was controlled using remote sensing imagery such as Landsat TM and DEM shaded relief images.展开更多
The northeastern Tibetan Plateau exhibits steep topography and strong internal or external dynamic geological effect and is frequently subjected to strong earthquakes and heavy rainfall.The geological evolution has re...The northeastern Tibetan Plateau exhibits steep topography and strong internal or external dynamic geological effect and is frequently subjected to strong earthquakes and heavy rainfall.The geological evolution has resulted in a wide distribution of ancient landslides,which has become a hotspot for studying ancient landslide formation and reactivation.In recent decades,several ancient landslides on both banks of the Longwu River,Qinghai Province,China were reactivated,causing serious economic losses and casualties.This study conducted remote sensing interpretation and ground surveys on these ancient landslides.Totally 59 ancient landslides were identified,and the formation mechanism,evolution process,and resurrection mechanism of the Longwu Xishan No.2 ancient landslide were analyzed by means of a detailed field geological survey,drilling,and series of experimental tests such as the particle size distribution test,the Xray diffraction test and the mechanical properties test.The results show that the formation of these ancient landslides is closely associated with the uplift of the Tibetan Plateau and the erosion of the Longwu River.Firstly,the intermittent uplift of the Tibetan Plateau lead to the diversion and downcutting of the Longwu River basin,which forms the alternate slope topography with steep and slow slopes,thereby providing favourable topography and slope structure conditions for the formation of landslides.Secondly,34.5%clay-mineral content in the Neoproterozoic mudstone with 32.7%particle size less than 0.005 mm,and the corrosion and softening effects of the Neogene mudstone with high clay mineral content under the erosion of water provides favourable material conditions for the formation of landslides.Thirdly,rainfall and human activities are the primary triggering factors for the revival of this ancient landslide group.It is revealed that the evolution process of the ancient landslides on both banks of the Longwu River can be divided into five stages namely tectonic rapid uplift slope formation,river erosion creep-sliding deformation,slope instability critical status,landslide failure-movement-accumulation,and slope reactivation under rainfall erosion and engineering excavation.展开更多
The province of Fujian on China’s southeast coast is severely impacted by typhoons.Based on coastal profile monitoring and 40 years of satellite data,this paper analyzed the response of coastal profiles to natural an...The province of Fujian on China’s southeast coast is severely impacted by typhoons.Based on coastal profile monitoring and 40 years of satellite data,this paper analyzed the response of coastal profiles to natural and anthropogenic forces along the northern part of Fujian’s coast.Results indicated that the pattern of coastal evolution differed largely on cross-shore profiles and longshore coastlines.Only a few sandy coasts were severely affected by extreme weather events in summer,such as typhoons and storm surges,which may result from the wind direction relative to the coast.The cross-shore profiles changed drastically while the mean high-water coastline remained stable.In contrast,anthropogenic forces had a dual effect due to artificial sand extraction and reclamation.Artificial sand extraction usually occurred on sandy coasts,resulting in a decrease in some local surface profiles of tens of centimeters to metres in two years.Reclamation had the main impact on muddy coasts,especially in bays,causing seaward progradation during the past 40 years.The impacts of human activities on muddy coasts were far greater than natural factors.Findings from our coastal monitoring study for both sandy and muddy coasts provide an important scientific basis for practical applications,such as Fujian coastal protection,coastal zone exploitation,and utilization planning.展开更多
Remote sensing images were used to reproduce the changes in wetland vegetation since 1987,and the potential impact of policy changes and human activities on vegetation restoration and biodiversity conservation in coas...Remote sensing images were used to reproduce the changes in wetland vegetation since 1987,and the potential impact of policy changes and human activities on vegetation restoration and biodiversity conservation in coastal wetlands was explored based on the landscape pattern index and the human disturbance index(HDI).The results showed that the vegetation displayed a zonal distribution pattern in which,perpendicular to the coastline early in the study period,the vegetation type changed from coastal wetland to bare mud flat with Spartina alterniflora,Suaeda glauca,and Phragmites australis as well as to constructed wetlands dominated by rice.Under the influence of human activities,the number of patches(NP)and mean nearest-neighbor distance(MNN)between patches gradually increased during the study period,while the mean patch size gradually decreased.The patch density increased from 179(1987)to 296 patches per ha(2013).Additionally,human activity in the study area intensified.The HDI increased from 0.353(1987)to 0.471(1987)and showed positive correlations(R^(2)>80%,p<0.01)with NP and MNN.Human activity,such as changes in land use,resulted in more fragmented vegetation patterns,and the nonzonal(intrazonal)distribution of the vegetation became more obvious in coastal wetlands.展开更多
This paper reviewed the developments of the last ten years in the field of international high-resolution earth observation, and introduced the developmental status and plans for China's high-resolution earth obser...This paper reviewed the developments of the last ten years in the field of international high-resolution earth observation, and introduced the developmental status and plans for China's high-resolution earth observation program. In addition, this paper expounded the transformation mechanism and procedure from earth observation data to geospatial information and geographical knowledge, and examined the key scientific and technological issues, including earth observation networks, high-precision image positioning, image understanding, automatic spatial information extraction, and focus services. These analyses provide a new impetus for pushing the application of China's high-resolution earth observation system from a "quantity" to "quality" change, from China to the world, from providing products to providing online service.展开更多
基金funded by the Basic Research Program of the Institute of Earthquake Forecasting,China Earthquake Administration(Grant Nos.CEAIEF20220102,2021IEF0505,and CEAIEF2022050502)the National Natural Science Foundation of China(Grant Nos.42072248 and 42041006)the National Key Research and Development Program of China(Grant Nos.2021YFC3000601-3 and 2019YFE0108900)。
文摘Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.
文摘With the rapid development of remote sensing technology, it has become a technical means of geological research and geological survey. Remote sensing can realize rapid and large area information extraction and provide effective method for geological hazard extraction. However, due to regional differences, there are some differences between geological hazard occurrence characteristics and extraction indexes in different regions. This paper takes Linjiang City, Jilin Province as an example to extract geological hazards with multisource data. The results show that the remote sensing method can realize the extraction of debris flow, collapse, landslide and other geological hazards in the study area, and obtain high accuracy.
基金National Natural Science Foundation of China,No.41871350,No.41571099Scientific and Technological Basic Resources Survey Project,No.2017FY 100900。
文摘The compilation of 1:250,000 vegetation type map in the North-South transitional zone and 1:50,000 vegetation type maps in typical mountainous areas is one of the main tasks of Integrated Scientific Investigation of the North-South Transitional Zone of China.In the past,vegetation type maps were compiled by a large number of ground field surveys.Although the field survey method is accurate,it is not only time-consuming,but also only covers a small area due to the limitations of physical environment conditions.Remote sensing data can make up for the limitation of field survey because of its full coverage.However,there are still some difficulties and bottlenecks in the extraction of remote sensing information of vegetation types,especially in the automatic extraction.As an example of the compilation of 1:50,000 vegetation type map,this paper explores and studies the remote sensing extraction and mapping methods of vegetation type with medium and large scales based on mountain altitudinal belts of Taibai Mountain,using multi-temporal high resolution remote sensing data,ground survey data,previous vegetation type map and forest survey data.The results show that:1)mountain altitudinal belts can effectively support remote sensing classification and mapping of 1:50,000 vegetation type map in mountain areas.Terrain constraint factors with mountain altitudinal belt information can be generated by mountain altitudinal belts and 1:10,000 Digital Surface Model(DSM)data of Taibai Mountain.Combining the terrain constraint factors with multi-temporal and high-resolution remote sensing data,ground survey data and previous small-scale vegetation type map data,the vegetation types at all levels can be extracted effectively.2)The basic remote sensing interpretation and mapping process for typical mountains is interpretation of vegetation type-groups→interpretation of vegetation formation groups,formations and subformations→interpretation and classification of vegetation types&subtypes,which is a combination method of top-down method and bottom-up method,not the top-down or the bottom-up classification according to the level of mapping units.The results of this study provide a demonstration and scientific basis for the compilation of large and medium scale vegetation type maps.
基金Sponsored by National Natural Science Foundation of China(41271060)
文摘Based on the ETM remote sensing images of Guangzhou City in 2014, the spatial distribution results o f three environmental factors including vegetation coverage(NDVI), soil index(vegetation index of bare soil) and sl ope were obtained. By using comprehensive index method, the normalized environmental factors were weighted and superimposed, and the fi nal evaluation results of ecological environment in Guangzhou City were obtained. The results showed that overall situation of natural ecological environment in Guangzhou was not optimistic, that is, the area of land with bad, moderate, good and superior environment accounted for 59.70%, 35.79%, 4.50% and around 0.01% of total area of land in Guangzhou City respectively. Ecological environment was generally poor in the central urban districts in the south of Guangzhou City, while it was relatively better in the north and northeast. Attaching importance to the constr uction of greenbelts and greenways is an effective way to improve regional environmental quality and natural ecological e nvironment level.
基金National Key Research and Development Program of China,No.2022YFC3204302China National Admin-istration of Coal Geology,No.ZMKJ-2021-ZX04。
文摘Ecological water supplement projects have been implemented in many coastal wetlands,influencing saltmarsh vegetation restoration by altering tidal creek development.To clarify the effectiveness of ecological water supplement on tidal creek development and saltmarsh vegetation restoration,time series of high-resolution remote sensing images from2000 to 2021 were used to extract and analyze tidal creeks and saltmarsh vegetation in the Diaokou Estuary Reserve.The results are summarized as follows:(1)All tidal creek indices,except curvature,exhibited a significant linear increase with time,while curvature initially decreased and increased afterwards.The 5-year cumulative ecological water supplement volume was significantly positively correlated(R^(2)>0.7)with all tidal creek indices.(2)During the same period,most landscape pattern metrics of Phragmites australis increased,while those of Tamarix chinensis initially increased and then declined.Although the class area(CA)of Suaeda salsa increased with time,its perimeter-area fractal dimension(PAFRAC)and aggregation index(AI)fluctuated.(3)The CA of P.australis and S.salsa was significantly positively correlated with most tidal creek indices except curvature,while that of T.chinensis showed no significant correlation with any tidal creek index.Moreover,the AI and PAFRAC of P.australis were significantly positively correlated with fractal dimension,frequency/curvature of tidal creeks,respectively,while those of S.salsa and T.chinensis exhibited no significant correlation.In summary,the ecological water supplement project enhanced tidal creek development in coastal wetlands,promoting the restoration of P.australis and S.salsa,while having little impact on the restoration of T.chinensis.
基金funded by the Basic Research program from the Institute of Earthquake Forecasting,China Earthquake Administration(Grant No.CEAIEF20240302)the National Natural Science Foundation of China(Grant Nos.42072248)the National Key Research and Development Program of China(Grant Nos.2021YFC3000600 and 2019YFE0108900)。
文摘Rapidly obtaining spatial distribution maps of secondary disasters triggered by strong earthquakes is crucial for understanding the disaster-causing processes in the earthquake hazard chain and formulating effective emergency response measures and post-disaster reconstruction plans.On April 3,2024,a M_(W)7.4 earthquake struck offshore east of Hualien,Taiwan,China,which triggered numerous coseismic landslides in bedrock mountain regions and severe soil liquefaction in coastal areas,resulting in significant economic losses.This study utilized postearthquake emergency data from China's high-resolution optical satellite imagery and applied visual interpretation method to establish a partial database of secondary disasters triggered by the 2024 Hualien earthquake.A total of 5348 coseismic landslides were identified,which were primarily distributed along the eastern slopes of the Central Mountain Range watersheds.In high mountain valleys,these landslides mainly manifest as localized bedrock collapses or slope debris flows,causing extensive damage to highways and tourism facilities.Their distribution partially overlaps with the landslide concentration zones triggered by the 1999 Chi-Chi earthquake.Additionally,6040 soil liquefaction events were interpreted,predominantly in the Hualien Port area and the lowland valleys of the Hualien River and concentrated within the IX-intensity zone.Widespread surface subsidence and sand ejections characterized soil liquefaction.Verified against local field investigation data in Taiwan,rapid imaging through post-earthquake remote sensing data can effectively assess the distribution of coseismic landslides and soil liquefaction within high-intensity zones.This study provides efficient and reliable data for earthquake disaster response.Moreover,the results are critical for seismic disaster mitigation in high mountain valleys and coastal lowlands.
基金supported by the National Natural Science Foundation of China project(No.42372339)the China Geological Survey Project(Nos.DD20221816,DD20190319)。
文摘On September 5,2022,a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage and substantial economic loss.In this study,we established a coseismic landslide database triggered by Luding Ms 6.8 earthquake,which includes 4794 landslides with a total area of 46.79 km^(2).The coseismic landslides primarily consisted of medium and small-sized landslides,characterized by shallow surface sliding.Some exhibited characteristics of high-position initiation resulted in the obstruction or partial obstruction of rivers,leading to the formation of dammed lakes.Our research found that the coseismic landslides were predominantly observed on slopes ranging from 30°to 50°,occurring at between 1000 m and 2500 m,with slope aspects varying from 90°to 180°.Landslides were also highly developed in granitic bodies that had experienced structural fracturing and strong-tomoderate weathering.Coseismic landslides concentrated within a 6 km range on both sides of the Xianshuihe and Daduhe fault zones.The area and number of coseismic landslides exhibited a negative correlation with the distance to fault lines,road networks,and river systems,as they were influenced by fault activity,road excavation,and river erosion.The coseismic landslides were mainly distributed in the southeastern region of the epicenter,exhibiting relatively concentrated patterns within the IX-degree zones such as Moxi Town,Wandong River basin,Detuo Town to Wanggangping Township.Our research findings provide important data on the coseismic landslides triggered by the Luding Ms 6.8 earthquake and reveal the spatial distribution patterns of these landslides.These findings can serve as important references for risk mitigation,reconstruction planning,and regional earthquake disaster research in the earthquake-affected area.
基金The research was supported by the National Innovation Research Group Science Fund(No.41521002)the National Key Research and Development Program of China(No.2018YFC1505202)。
文摘Geohazard recognition and inventory mapping are absolutely the keys to the establishment of reliable susceptibility and hazard maps. However, it has been challenging to implement geohazards recognition and inventory mapping in mountainous areas with complex topography and vegetation cover. Progress in the light detection and ranging(Li DAR) technology provides a new possibility for geohazard recognition in such areas. Specifically, this study aims to evaluate the performances of the Li DAR technology in recognizing geohazard in the mountainous areas of Southwest China through visually analyzing airborne Li DAR DEM derivatives. Quasi-3 D relief image maps are generated based on the sky-view factor(SVF), which makes it feasible to interpret precisely the features of geohazard. A total of 146 geohazards are remotely mapped in the entire 135 km^(2) study area in Danba County, Southwest China, and classified as landslide, rock fall, debris flow based on morphologic characteristics interpreted from SVF visualization maps. Field validation indicate the success rate of Li DAR-derived DEM in recognition and mapping geohazard with higher precision and accuracy. These mapped geohazards lie along both sides of the river, and their spatial distributions are related highly to human engineering activities, such as road excavation and slope cutting. The minimum geohazard that can be recognized in the 0.5 m resolution DEM is about 900 m^(2). Meanwhile, the SVF visualization method is demonstrated to be a great alternative to the classical hillshaded DEM method when it comes to the determination of geomorphological properties of geohazard. Results of this study highlight the importance of Li DAR data for creating complete and accurate geohazard inventories, which can then be used for the production of reliable susceptibility and hazard maps and thus contribute to a better understanding of the movement processes and reducing related losses.
基金supported by the National Natural Science Foundation of China(Project No.41807448).
文摘Wind erosion,or the transportation and deposition of sand into desert dunes and aeolian loess,is one of the most important aeolian activities.The progression of aeolian landforms expands arid and barren landscapes,leading to the degradation of adjacent areas.The Gonghe Basin,as a typical plateau with abundant sand sources,is highly sensitive to changes in the local climate conditions.In order to quantify the spatial-temporal variations in the aeolian landforms in the Gonghe Basin,we conducted field surveys and also analyzed twelve remote sensing(Landsat5 TM and Landsat8 OLI)images that sample the Gonghe Basin from 1989 to 2019.In the Gonghe Basin,we identified aeolian landforms such as climbing dunes on the windward slopes of the foothills,checkerboard dunes in the southeastern part of the basin,flat dunes,parabolic dunes and crescent dunes on the east and west sides of Longyangxia Reservoir,shrubby sandbanks on the valley slope in Shazhuyu,Tanggemu,and Indel,and sandy thickets at the bottom of the valley near the Dalian Sea,the Longyangxia Reservoir,and the tributaries of the Yellow River.From 1989 to 2005,the area of the aeolian regions expanded by 816.7 km2,with an annual conversion rate of 0.05%.From 2015 to 2019,the area of the aeolian regions shrunk by 2411.9 km2,with an annual conversion rate of−0.15%.The number and size of the fixed and semi-fixed dunes(e.g.the shrubby sandbanks on the valley slope and the sandy thickets at the bottom of the valley)were more stable than those of the mobile dunes(e.g.the checkerboard dunes,the flat dunes,the crescent dunes,the parabolic dunes,and the climbing dunes).The fixed and semi-fixed dunes were arranged in an irregular ring shape,and the location of the center of gravity of this ring did not change significantly from 1989 to 2019;in this time,the mobile dunes migrated to the northwest.
基金the Natural Science Foundation of Southwest University of Science and Technology(18zx7117)the National Science and Technology Support Program of China(2015BAC05B05-01)。
文摘As climate change intensifies,finding an ecological indicator to quickly and accurately reflect the impact on mountain ecosystems is necessary.The low treeline/timberline,highly sensitive to climate variability and changes significantly within 5–10years,provides a new way to study the response to regional climate variability.This study explored the distribution and vertical displacement patterns of the low treeline in the Upper Minjiang River of China,using SPOT remote sensing images in 1999 and 2013and long-term positional observations.Using the Geodetector model,the study investigated the dominant climatic factors influencing the low treeline displacement.The results showed that the low treeline was located at 1700–3200 m elevation on sunny slopes(southeast,south,southwest,and west slopes)with slopes over 25°.From 1999 to 2013,the low treeline moved downward by 6 m from 2561±264m to 2555±265 m,along with a warm–humid climate tendency.The downward displacement was greater on slopes over 25°and shady slopes(-20 m and-10 m,respectively)than on slopes≤25°and sunny slopes.Additionally,the downward was greater in the warm and humid Zagunao River Basin(-15 m)compared to the arid valley center(-7 m)and the cold Heishui River Basin(-3 m).Meanwhile,the low treeline displacement correlated negatively with precipitation and relative humidity variations at the significance level of 0.05,with correlation coefficients of-0.572and-0.551,respectively.Variations in relative humidity and temperature significantly affected the spatial differentiation of low treeline displacement with influencing power of 0.246(p=0.036<0.05)and 0.183(p=0.032<0.05),respectively.Thus,the low treeline is a moisture-limited line,and its formation and variation are closely related to regional water–heat balance.The study clarifies the indicative value of the low treeline for climate variability in mountain areas and can provide references for ecological restoration in arid valleys.
文摘The Geological Map of Colombia 2015 summarizes the superficial geological information of Colombia.It is the final product of a process of integration and generalization of the cartographic information of the existing geological maps published by the Colombian Geological Survey complemented by the interpretation of remote sensing imagery of previously unmapped areas.Harmonization was controlled using remote sensing imagery such as Landsat TM and DEM shaded relief images.
基金financially supported by the National Natural Science Foundation of China(grant numbers 41907238 and 41931296)National Key R&D Program of China(grant numbers 2018YFC1508804)+1 种基金Sichuan Science and Technology Program(grant numbers 2019YJ0534 and 2021YFSY0036)State Key Laboratory of Geohazard Prevention and Geo-environment Protection Independent Research Project(SKLGP2021Z008)。
文摘The northeastern Tibetan Plateau exhibits steep topography and strong internal or external dynamic geological effect and is frequently subjected to strong earthquakes and heavy rainfall.The geological evolution has resulted in a wide distribution of ancient landslides,which has become a hotspot for studying ancient landslide formation and reactivation.In recent decades,several ancient landslides on both banks of the Longwu River,Qinghai Province,China were reactivated,causing serious economic losses and casualties.This study conducted remote sensing interpretation and ground surveys on these ancient landslides.Totally 59 ancient landslides were identified,and the formation mechanism,evolution process,and resurrection mechanism of the Longwu Xishan No.2 ancient landslide were analyzed by means of a detailed field geological survey,drilling,and series of experimental tests such as the particle size distribution test,the Xray diffraction test and the mechanical properties test.The results show that the formation of these ancient landslides is closely associated with the uplift of the Tibetan Plateau and the erosion of the Longwu River.Firstly,the intermittent uplift of the Tibetan Plateau lead to the diversion and downcutting of the Longwu River basin,which forms the alternate slope topography with steep and slow slopes,thereby providing favourable topography and slope structure conditions for the formation of landslides.Secondly,34.5%clay-mineral content in the Neoproterozoic mudstone with 32.7%particle size less than 0.005 mm,and the corrosion and softening effects of the Neogene mudstone with high clay mineral content under the erosion of water provides favourable material conditions for the formation of landslides.Thirdly,rainfall and human activities are the primary triggering factors for the revival of this ancient landslide group.It is revealed that the evolution process of the ancient landslides on both banks of the Longwu River can be divided into five stages namely tectonic rapid uplift slope formation,river erosion creep-sliding deformation,slope instability critical status,landslide failure-movement-accumulation,and slope reactivation under rainfall erosion and engineering excavation.
基金funded by the NSFC-Shandong Joint Fund for Marine Science Research Centers(U1606401)the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology(No.MGQNLM201709)+1 种基金the China Postdoctoral Science Foundation(No.2016M600558)the China Geological Survey(No.DD20160137).
文摘The province of Fujian on China’s southeast coast is severely impacted by typhoons.Based on coastal profile monitoring and 40 years of satellite data,this paper analyzed the response of coastal profiles to natural and anthropogenic forces along the northern part of Fujian’s coast.Results indicated that the pattern of coastal evolution differed largely on cross-shore profiles and longshore coastlines.Only a few sandy coasts were severely affected by extreme weather events in summer,such as typhoons and storm surges,which may result from the wind direction relative to the coast.The cross-shore profiles changed drastically while the mean high-water coastline remained stable.In contrast,anthropogenic forces had a dual effect due to artificial sand extraction and reclamation.Artificial sand extraction usually occurred on sandy coasts,resulting in a decrease in some local surface profiles of tens of centimeters to metres in two years.Reclamation had the main impact on muddy coasts,especially in bays,causing seaward progradation during the past 40 years.The impacts of human activities on muddy coasts were far greater than natural factors.Findings from our coastal monitoring study for both sandy and muddy coasts provide an important scientific basis for practical applications,such as Fujian coastal protection,coastal zone exploitation,and utilization planning.
基金supported by the Natural Science Foundation of China(41471431).
文摘Remote sensing images were used to reproduce the changes in wetland vegetation since 1987,and the potential impact of policy changes and human activities on vegetation restoration and biodiversity conservation in coastal wetlands was explored based on the landscape pattern index and the human disturbance index(HDI).The results showed that the vegetation displayed a zonal distribution pattern in which,perpendicular to the coastline early in the study period,the vegetation type changed from coastal wetland to bare mud flat with Spartina alterniflora,Suaeda glauca,and Phragmites australis as well as to constructed wetlands dominated by rice.Under the influence of human activities,the number of patches(NP)and mean nearest-neighbor distance(MNN)between patches gradually increased during the study period,while the mean patch size gradually decreased.The patch density increased from 179(1987)to 296 patches per ha(2013).Additionally,human activity in the study area intensified.The HDI increased from 0.353(1987)to 0.471(1987)and showed positive correlations(R^(2)>80%,p<0.01)with NP and MNN.Human activity,such as changes in land use,resulted in more fragmented vegetation patterns,and the nonzonal(intrazonal)distribution of the vegetation became more obvious in coastal wetlands.
基金supported by National Basic Research Program of China(Grant No. 2012CB719906)
文摘This paper reviewed the developments of the last ten years in the field of international high-resolution earth observation, and introduced the developmental status and plans for China's high-resolution earth observation program. In addition, this paper expounded the transformation mechanism and procedure from earth observation data to geospatial information and geographical knowledge, and examined the key scientific and technological issues, including earth observation networks, high-precision image positioning, image understanding, automatic spatial information extraction, and focus services. These analyses provide a new impetus for pushing the application of China's high-resolution earth observation system from a "quantity" to "quality" change, from China to the world, from providing products to providing online service.
