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对1966―2007年正式出版的《中国震例》中云南定点形变异常震例进行统计分析,发现云南地区6级以上地震前均有形变异常,且随着发震时间的逼近,定点形变异常数量有增加趋势。对2000—2015年云南定点形变观测异常进行分析,发现云南及其邻区6级以上地震发生前,定点形变均有显著异常出现。当显著形变异常数量N≥2,1年内云南及其邻区发生6级以上地震的概率可达75%。6~6.5级地震震前形变异常分布的震中距最远为470 km,7级地震达到700 km,且具有震级越大分布范围越广的特征。因此,形变异常台站数量可以作为云南及其邻区有6级以上地震的中短期预测指标。 相似文献
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本文通过收集整理三河—平谷地震区的地震目录、GPS测量和周边台站的地电、地磁、地下水、水温及钻孔形变观测资料,绘制了相应的图件,对该区的地球物理特征进行了研究.结果表明,区内夏垫—三河附近小震活动频繁,震源深度较浅,地震活动明显受断裂构造控制;周边台站的电、磁、水、温和形变在地震发生前后大部分有前兆异常现象,且特征各异,其特征和异常与三河—平谷地震区的构造运动及该区的地震活动有着密切关系,这些地球物理场特征可为今后的台站观测提供基础,将各方面的特征综合考虑,会对地震前兆信息的观测和识别具有一定的意义,进而为该区的地质构造运动特征、地震监测预测和防灾减灾工作提供地质和地球物理方面的依据. 相似文献
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结合GNSS和黑龙江地区定点形变观测,分析日本2011年3月11日Mw9.0地震对黑龙江地区地壳形变的影响.结果显示:日本Mw9.0地震引起哈尔滨站、绥阳站震后2年内运动速率明显增加(哈尔滨站增大4 mm/a,绥阳站速率增大6 mm/a);定点形变与GPS观测到的同震效应至少在4个台站多种仪器均具有较好的一致性;日本Mw 9.0地震不仅引起区域水平向应变变化,对垂直向也产生一定影响;长基线变化反映出日本Mw9.0地震引起的大空间尺度应变变化与黑龙江地区长期构造应力场背景一致,该地震对黑龙江地区地表应变积累可能有增强影响. 相似文献
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本文以中国大陆西部定点形变观测资料作为研究对象, 采用S变换和超限率时频分析法对其进行了处理和分析。 研究结果表明: 在2008年汶川MS8.0地震前, 距离震中600 km范围内的定点形变个别台站观测到高频异常, 异常持续时间较长; 距离震中300 km范围的个别台站临震高频异常非常显著; 并且不同的定点形变观测手段对高频信号的响应不同, 地倾斜测项临震前高频异常形态较地应变测项更为清晰灵敏。 同时S变换和超限率两种方法处理结果具有较好的一致性, 表明本文提取到的高频异常可信度较高。 相似文献
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2008年8月30日的攀枝花仁和—凉山州会理间6.1级地震前,距离最近的攀枝花南山定点形变台多套仪器监测到了明显的异常变化。本文对此次6.1级地震前的多套形变仪器记录异常作了总结研究,各套仪器监测在出现中期异常的同时,又存在短临异常。结果表明:南山地震台石英摆仪观测NS向分量存在趋势变化偏小异常的同时,又存在短期突变加速异常;长水管仪的异常变化表现为加速和转向变化;石英伸缩仪NS向分量的异常变化在震前两天出现,表现为原始记录曲线、整点值的畸变。结合历史震例总结显示:攀枝花南山台各套形变监测短临异常的开始或结束时间对台站周边未来地震的时间有一定指示意义,即异常开始后一至两个月内,在监测台站周边地区可能发生6级以上地震;各监测分量方向异常变化对台站周边未来地震可能的方位也有一定的指示意义;异常的变化幅度与未来地震震级关系不明显。 相似文献
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利用内蒙古地区5套VP垂直摆倾斜仪2019—2021年连续3年的观测数据,采用功率谱密度（PSD）分析方法,分别计算其在地震频段（200～600 s）的地震噪声水平（SNM）,直观化对比分析了内蒙古地区VP垂直摆背景噪声水平。结果表明：3套仪器的背景噪声水平较低,2套仪器的背景高噪声水平偏高,在区域分布上未见明显规律;低噪声水平仪器观测曲线光滑、固体潮清晰,所在台站观测环境优异、稳定;高噪声水平仪器观测曲线毛刺多、不光滑,所在台站洞体条件较差,长时间受到大风、振动干扰,且1套仪器长期存在观测系统问题。通过分析不同台站VP垂直摆的背景噪声特征,为新建仪器的选址及观测数据的解释和分析提供了依据。 相似文献
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特大远震引起的形变观测变化图像 总被引：3，自引：0，他引：3
利用定点长水管倾斜仪、石英伸缩仪、金属摆倾斜仪、石英摆倾斜仪连续观测资料对特大远震引起的震时和震后形变效应进行了分析.分析结果表明定点连续形变观测台网能记录到不同方位地震的震时脉冲信号,其持续时间半小时到4小时;同时还能记录到一些地震的阶跃信号.水平摆倾斜仪（金属摆、石英摆）观测值的震后效应表现为大幅漂移,持续时间几天到一个月.对由特大远震引起的形变观测变化图像出现差异的原因进行了讨论.另外对震时阶跃变化图像、定点形变观测仪器长趋势的漂移项、观测台站所处的地质构造三者之间的关系进行了讨论. 相似文献
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北方半干旱区土地利用/覆被变化对湖泊水质的影响:以岱海流域为例(2000—2018年) 总被引：2，自引：0，他引：2
土地利用/覆被变化对明晰气候变化和人类活动对湖泊水环境的影响有重要作用.以北方典型农牧交错的岱海流域为研究对象,基于遥感解译技术、马尔可夫转移矩阵、综合污染指数法等方法,对2000-2018年岱海流域土地利用/覆被和湖泊水质的变化进行分析,并结合冗余分析法和计量分析模型探究长时间序列尺度下土地利用/覆被变化对湖泊水质的影响.结果表明:近20年来,岱海流域的土地利用/覆被类型以耕地和草地为主,其变化特征主要是草地和林地转化为耕地,水域转化为季节性河流,岱海转化为内陆滩涂、沼泽草地和灌丛沼泽;岱海湖泊水质因子高锰酸盐指数、五日生化需氧量、总磷和总氮浓度存在不同程度的超标现象;岱海、湿地、林地对水质具有积极的改善作用,耕地、草地、建设用地是加剧水质污染的主要原因.该研究为岱海湖泊流域土地资源合理利用、湖泊水质改善和生态保护提供了一定的科学理论依据. 相似文献
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This study aims to quantify the contribution of land use/cover change (LUCC) during the last three decades to climate change conditions in eastern China. The effects of farmland expansion in Northeast China, grassland degradation in Northwest China, and deforestation in South China were simulated using the Weather Research and Forecasting (WRF) model in addition to the latest actual land cover datasets. The simulated results show that when forestland is converted to farmland, the air temperature decreased owing to an increase in surface albedo in Northeast China. The climatic effect of grassland degradation on the Loess Plateau was insignificant because of the negligible difference in albedo between grassland and cropland. In South China, deforestation generally led to a decrease in temperature. Furthermore, the temperature decrease caused by the increase in albedo counteracted the warming effects of the evapotranspiration decrease, so the summer temperature change was not significant in South China. Excluding the effects of urbanization in the North China Plain, the LUCC effects across the entire region of East China presented an overall cooling trend. However, the variation in temperature scale and magnitude was less in summer than that in winter. This result is due mainly to the cooling caused by the increase in albedo offset partly by the increase in temperature caused by the decrease in evaporation in summer. Summer precipitation showed a trend of increasing–decreasing–increasing from southeast to northwest after LUCC, which was induced mainly by the decrease in surface roughness and cyclone circulations appearing northwest of Northeast China, in the middle of the Loess Plateau, and in Yunnan province at 700 hPa after forests were converted into farmland. All results will be instructive for understanding the influence of LUCC on regional climate and future land planning in practice. 相似文献
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Land‐cover/climate changes and their impacts on hydrological processes are of widespread concern and a great challenge to researchers and policy makers. Kejie Watershed in the Salween River Basin in Yunnan, south‐west China, has been reforested extensively during the past two decades. In terms of climate change, there has been a marked increase in temperature. The impact of these changes on hydrological processes required investigation: hence, this paper assesses aspects of changes in land cover and climate. The response of hydrological processes to land‐cover/climate changes was examined using the Soil and Water Assessment Tool (SWAT) and impacts of single factor, land‐use/climate change on hydrological processes were differentiated. Land‐cover maps revealed extensive reforestation at the expense of grassland, cropland, and barren land. A significant monotonic trend and noticeable changes had occurred in annual temperature over the long term. Long‐term changes in annual rainfall and streamflow were weak; and changes in monthly rainfall (May, June, July, and September) were apparent. Hydrological simulations showed that the impact of climate change on surface water, baseflow, and streamflow was offset by the impact of land‐cover change. Seasonal variation in streamflow was influenced by seasonal variation in rainfall. The earlier onset of monsoon and the variability of rainfall resulted in extreme monthly streamflow. Land‐cover change played a dominant role in mean annual values; seasonal variation in surface water and streamflow was influenced mainly by seasonal variation in rainfall; and land‐cover change played a regulating role in this. Surface water is more sensitive to land‐cover change and climate change: an increase in surface water in September and May due to increased rainfall was offset by a decrease in surface water due to land‐cover change. A decrease in baseflow caused by changes in rainfall and temperature was offset by an increase in baseflow due to land‐cover change. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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XuChao Yang YiLi Zhang LinShan Liu Wei Zhang MingJun Ding ZhaoFeng Wang 《中国科学D辑(英文版)》2009,52(8):1207-1215
Using CRU high resolution grid observational temperature and ERA40 reanalysis surface air temperature data during 1960–1999,
we investigated the sensitivity of surface air temperature change to land use/cover types in China by subtracting the reanalysis
from the observed surface air temperature (observation minus reanalysis, OMR). The results show that there is a stable and
systemic impact of land use/cover types on surface air temperature. The surface warming of each land use/cover type reacted
differently to global warming. The OMR trends of unused land (⩾0.17 °C/decade), mainly comprised by sandy land, Gobi and bare
rock gravel land, are obviously larger than those of the other land use/cover types. The OMR over grassland, farmland and
construction land shows a moderate decadal warmingabout 0.12°C/decade, 0.10°C/decade, 0.12°C/decade, respectively. Woodland
areas do not show a significant warming trend (0.06°C/decade). The overall assessment indicates that the surface warming is
larger for areas that are barren and anthropogenically developed. The better the vegetation cover, the smaller the OMR warming
trend. Responses of surface air temperature to land use/cover types with similar physical and chemical properties and biological
processes have no significant difference. The surface air temperature would not react significantly until the intensity of
land cover changes reach a certain degree. Within the same land use/cover type, areas in eastern China with intensive human
activities exhibit larger warming trend. The results provide observational evidence for modeling research on the impact of
land use/cover change on regional climate. Thus, projecting further surface climate of China in regional scale should not
only take greenhouse gas increase into account, but also consider the impact of land use/cover types and land cover change.
Supported by National Basic Research Program of China (Grant No. 2005CB422006), National Natural Science Foundation of China
(Grant Nos. 90202012, 40771206) 相似文献
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Changes in climate and land use can significantly influence the hydrological cycle and hence affect water resources. Understanding the impacts of climate and land‐use changes on streamflow can facilitate development of sustainable water resources strategies. This study investigates the flow variation of the Zamu River, an inland river in the arid area of northwest China, using the Soil and Water Assessment Tool distributed hydrological model. Three different land‐use and climate‐change scenarios were considered on the basis of measured climate data and land‐use cover, and then these data were input into the hydrological model. Based on the sensitivity analysis, model calibration and verification, the hydrological response to different land‐use and climate‐change scenarios was simulated. The results indicate that the runoff varied with different land‐use type, and the runoff of the mountain reaches of the catchment increased when grassland area increased and forestland decreased. The simulated runoff increased with increased precipitation, but the mean temperature increase decreased the runoff under the same precipitation condition. Application of grey correlation analysis showed that precipitation and temperature play a critical role in the runoff of the Zamu River basin. Sensitivity analysis of runoff to precipitation and temperature by considering the 1990s land use and climate conditions was also undertaken. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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A regional climate model (RegCM3) nested within ERA40 re-analyzed data is used to investigate the climate effects of land use change over China. Two 15-year simulations (1987―2001), one with current land use and the other with potential vegetation cover without human intervention, are conducted for a domain encompassing China. The climate impacts of land use change are assessed from the difference between the two simulations. Results show that the current land use (modified by anthropogenic ac- tivities) influences local climate as simulated by the model through the reinforcement of the monsoon circulation in both the winter and summer seasons and through changes of the surface energy budget. In winter, land use change leads to reduced precipitation and decreased surface air temperature south of the Yangtze River, and increased precipitation north of the Yangtze River. Land use change signifi- cantly affects summer climate in southern China, yielding increased precipitation over the region, de- creased temperature along the Yangtze River and increased temperature in the South China area (south-end of China). In summer, a reduction of precipitation over northern China and a temperature rise over Northwest China are also simulated. Both daily maximum and minimum temperatures are affected in the simulations. In general, the current land use in China leads to enhanced mean annual precipitation and decreased annual temperature over south China along with decreased precipitation over North China. 相似文献
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Farming and forestry land use changes in China and their driving forces from 1900 to 1980 总被引：1，自引：1，他引：1
GE Quansheng & DAI Junhu Institute of Geographic Sciences Natural Resources Research Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2005,48(10)
As the joint project of IGBP (International Geo-sphere-Biosphere Programme) and IHDP (Interna-tional Human Dimensions Programme on Global En-vironmental Change), LUCC (Land Use/Land Cover Change) has been the focus of geographic studies, not only because it is one of the main contents of global environmental change studies, the linkage between physical and human sciences[1], but also because it has a close relationship with some elements’ cycles inside terrestrial ecosystem, such as… 相似文献
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Modelling and analysis of the impact of irrigation on local arid climate over northwest China 总被引：1，自引：0，他引：1
This study focuses on how irrigation processes affect local climate over arid areas. The chosen study area is northwest China, a typical arid region where three dominant land‐use types are irrigated cropland, grassland, and desert. Observational analysis indicates that the highest precipitation, the coolest surface temperatures, and the slowest warming trend are seen over irrigated cropland from 1979 to 2005. The single column atmospheric model (SCAM), developed by the National Center for Atmospheric Research (NCAR), was used to investigate and better understand the differences in long‐term climate conditions and change over the above three land‐use types. The results indicate that local climate conditions are predominantly controlled by large‐scale forcing in this arid region and that local land surface forcing related to vegetation cover change and irrigation processes also has a significant impact. This study strongly suggests that a realistic climate forecast for this region can be achieved only with both accurate large‐scale and local climate forcing. The irrigated cropland of the region generates stronger evaporation that cools the surface and slows the warming trend more than does the evaporation from the natural grassland and desert. Stronger evaporation also significantly increases precipitation, potentially alleviating the stress of irrigation demands in arid regions. A series of sensitivity SCAM simulations indicate that a drier and warmer climate occurs with decreasing vegetation cover in the irrigated cropland region. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Carbon emissions induced by cropland expansion in Northeast China during the past 300 years 总被引：1，自引：0，他引：1
Assessments of the impacts of land use and land cover changes(LUCC) on the terrestrial carbon budget, atmospheric CO2 concentration, and CO2-related climatic change are important to understand the environmental effects of LUCC and provide information about the effects of historical carbon emissions. Using regional land cover reconstructions from historical records, with a bookkeeping model, we estimated the carbon sink changes caused by historical cropland expansion in Northeast China during the past 300 years. The conclusions are as follows:(1) There was a dramatic land reclamation of cropland during the past 300 years in Northeast China. Approximately 26% of the natural land was cultivated, and 38% of the grassland and 20% of the forest and shrubland were converted to cropland.(2) The carbon emission induced by cropland expansion between 1683 and 1980 was 1.06–2.55 Pg C, and the estimation from the moderate scenario was 1.45 Pg C. The carbon emissions of the soil carbon pool was larger than that from the vegetation carbon pool and comprised more than 2/3 of the total carbon emissions.(3) The carbon emissions of the three provinces in Northeast China were different. Heilongjiang Province had the largest carbon emissions, and Jilin Province had the second largest emissions.(4) The primary source of carbon emissions was forest reclamation(taking 60% of the total emissions in the moderate scenario), the secondary source was grassland cultivation(taking 27%), and the tertiary sources were shrubland and wetland reclamation(taking 13%). Examination on the data accuracy revealed that the high-resolution regional land cover data allowed the carbon budget to be evaluated at the county level and improved the precision of the results. The carbon emission estimation in this study was lower than those in previous studies because of the improved land use data quality and various types of land use change considered. 相似文献
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Climate moderates potential shifts in streamflow from changes in pinyon‐juniper woodland cover across the western U.S. 
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下载免费PDF全文 Pinyon‐juniper (PJ) cover has increased up to 10‐fold in many parts of the western U.S. in the last 140+ years. The impacts of these changes on streamflows are unclear and may vary depending on the intra‐annual distribution and amount of precipitation. Given the importance of streamflow in the western U.S., it is important to understand how shifts in PJ woodland cover may produce changes in streamflow across the region's diverse hydroclimates. To this end, we simulated the land surface water balance with contrasting woodland and grassland cover with the Hydrologiska Byråns Vattenbalansavdelning (HBV) model at a 4‐km resolution across the distribution of PJ woodlands in the western U.S. We used shifts in evapotranspiration (ET) between woodland and grassland cover as a proxy for potential changes in streamflows. Comparison of HBV model results with paired catchment studies indicated the model reasonably simulated annual decreases in ET with changes from woodland to grassland cover. For the northern and western ecoregions of the PJ distribution in the western U.S. where precipitation predominantly occurs in the winter, HBV simulated a 25 mm (37%) annual decrease in ET with conversion to grassland from woodland. Conversely, in southern ecoregions of PJ distribution with prominent summer monsoons, annual differences in ET were only 6 mm (19%). Our results suggest that only 29% of the PJ distribution, compared to an estimated 45% based on precipitation amount alone, has the potential for meaningful increases in streamflow with land cover change from woodland to grassland. 相似文献