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1.
《地震地质》2016,(3)
地震发生前普遍存在的热红外辐射异常现象,是当前评估区域发震危险性的重要参数之一。然而,并非所有的地表红外异常都与构造活动或地震有关,如何排除非构造因素对地表热红外辐射的影响,从强噪声背景中提取微弱信号,是当前利用热红外遥感技术研究构造活动的难点。地表温度(LST)背景场是热异常提取的基础,而以往研究中所建立的背景场不能有效反映当年气候变化对其的影响,造成热异常提取精度受限。为此,文中在提取热异常的过程中对背景场进行了改进,结合地表温度时间序列的周期性特征,引入谐波分析,采用傅里叶逼近的方法拟合地表温度离散时序,从中提取其年趋势,建立1个动态的、同时包含局地信息和年际特征的、更加可靠的地表温度背景场;将其引入RST模型,基于"kσ"准则识别地震热异常信息;最终采用异常方向、异常强度和距离指数这3个指标对异常结果进行分析,验证算法的有效性。利用MODIS地表温度产品,基于所提算法对2008年汶川地震进行了再研究,结果表明:1)汶川地震前存在明显的热异常,沿龙门山断裂呈带状分布,持续时间较长;2)发震期无明显的异常现象;3)震后热异常的发生具有循环往复性,但异常幅度和影响范围明显缩小。与传统的空间温度均值RST算法异常提取结果相比,文中方法所提取的热异常在空间分布上与活动断裂带更为吻合,对异常的产生消散过程刻画更加细致,表明以地表温度年趋势作为地震构造热异常提取的背景场更加可靠。 相似文献
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3.
利用华北北部（113～119E,38～42N）的NOAA-AVHRR 热红外通道数据,采用震兆红外异常监测快速处理系统软件,对遥感数据进行了辐射校正、几何校正和大气校正等处理,反演地表温度;结合地质状况,排除干扰因素的影响,利用图象差值法提取热红外温度异常;并以张北6.2级地震为例,总结了热红外异常的时空变化特征及其与地震预报的关系．
在张北地震前十几天,沿张家口——渤海地震带上出现了较大范围的热红外温度异常现象,异常区域呈条带状,具有一定的区域性的构造背景;异常在空间上从外围向震中发展,震中位于热红外异常增温区边缘．利用临震前出现的卫星热红外异常进行地震预报探索,有可能为地震预报开拓一条新的观测途径． 相似文献
4.
为了从海量遥感数据中有效地提取地表水体信息,并提高自动化提取效率,提出了一种基于遥感特征指数的地表水体自动提取方法.该方法选取归一化植被指数(NDVI)、归一化建筑指数(NDBI)和修正归一化水体指数(MNDWI)作为遥感特征指数集,并根据这些指数构建了遥感特征指数曲线.通过分析,发现地表水体在特征曲线中单调上升,植被在特征曲线中单调下降,而其它地物并无此特征.因此,根据这一规律,利用ERDAS IMAGINE软件建立了自动化提取模型.通过与其他方法对比,表明所建立的模型在精度和自动化方面都明显优于其他方法,可用于海量数据地表水体的自动提取.最后,在ARCGIS环境下,并通过决策树模型初步实现了地表水体的自动分类. 相似文献
5.
基于“网状塑性流动”大陆动力学模型和中国大陆大地热流的分布特征,文中针对网带黏性剪切热效应的平衡态,通过热力学能量方程的求解,导出网带温度异常方程等关系式,并通过与网带热流正异常的拟合分析,确定了相关的参数值。研究表明,塑性流动网带黏性剪切热的产生为温度的正异常提供了热源,并通过热传导扩展网带的影响范围,形成相应的热异常网带。作为对中东亚塑性流动网络系统平均状况的估计,网带的热异常宽度与地震带所显示的网带视宽度一致,约为65km;剪切网带的宽度为44km,约为网带热异常宽度的23;网带中线处的温度正异常约为210K,剪切网带边界处的温度正异常约为67K,至热异常带边缘处降低为零,其起伏形态与网带大地热流正异常“凸峰”相一致。文中为岩石圈下层塑性流动网络的存在及其对大地热流正异常分布的控制提供了理论依据 相似文献
6.
对祁连山地震带1991—2004年间发生的13次中强地震,采用NOAA卫星热红外遥感资料数据库进行地面温度的时空网格化扫描,获得多年连续的热红外时序,研究地震前后的温度演化过程,提取震前地表温度的异常特征。研究结果表明,有38%的地震在震前出现了热红外异常现象,有的表现为温度降低,有的则表现为温度升高,体现了地震诱发因素的复杂性;温度异常幅度均为2~3℃,异常出现的时间均在2个月内;震级越大,异常越明显,但并非所有6级以上地震都比5~6级地震的热红外异常明显。 相似文献
7.
非构造活动或非地震因素对地表热辐射场（地表温度）的影响,对于利用卫星热红外遥感探索地震前兆抑或断层活动有着重要的现实意义.地表温度中,典型非构造活动或非地震因素成份有：由太阳辐射引起的稳定年周期成份和与地形、纬度及能量平衡等因素有关的长期稳定成份,合称年变基准场.本文根据2000～2008年的MODIS/Terra地表温度产品,利用小波分析提取了中国大陆地表温度的年变基准场.在此基础上,结合热传导方程和数学物理方法,获得了年变基准场的（半）定量化表达式.进一步, 利用地表温度的长期稳定成份,获得了温度与海拔、纬度变化之间的定量关系：海拔每增加100 m,温度降低0.51±0.01 K; 纬度每增加1°,温度降低0.77±0.08 K.总之,年变基准场可为利用热红外辐射提取地壳活动信息提供一种参考背景, 温度与海拔、纬度变化之间的定量关系则可用来校正地形起伏和纬度变化对地表温度的影响. 相似文献
8.
利用NOAA—AVHRR数据通过Becker ＆ Li地温计算模型反演，得到有关地震发生前后每日的地表温度分布图像，然后进行逐日的地表温度分布图像以及震源区地表温度平均值日变时序曲线分析。结果表明震前出现了较明显的热红外地震前兆异常。最后指出，从NOAA—AVHRR数据中利用分裂窗技术反演陆地表面温度结果容易受到云层的干扰，但是更高空间分辨率和光谱分辨率的EOS／MODIS数据的产生以及由于EOS／AMSU能够透过云层探测到地表亮温，必将使卫星遥感热红外信息在地震监测预报中的应用范围及深度上得以拓展。 相似文献
9.
地表热红外辐射的影响因素较多,不仅受到构造活动的影响,还受到大气、太阳以及植被等多种因素的干扰.如何排除这些因素的干扰,是热红外遥感用于研究断层活动或者地震活动的难点之一.从频率域看,地表热红外辐射主要存在3种频段：(1)高频, 周期小于1年的天气变化;(2)中频,以1年周期为主的太阳、植被与季节变化; (3)低频,大于1年周期的大气变化的长周期成份,地壳缓慢的运动引起的热辐射变化亦属于长周期变化.本文运用小波理论将地表热红外辐射分解为上述3个频率成份,并结合气象资料和地震活动进行综合分析.结果表明,低频成份的热异常更接近于断层活动所引起的热信息,能为断层或地震活动提供一定的指示信息.低频成份的高温异常区(条带)跟构造特征、地震活动密切相关. 相似文献
10.
青藏高原地区高精度的土壤水分反演对高原能水循环、全球大气循环研究有着极大的影响.因此,获取青藏高原土壤水分时空布信息是一个迫切需要解决的问题.温度植被干旱指数(TVDI),是基于光学与热红外遥感通道数据反演土壤水分的重要方法,但在研究区域较大、地表覆盖格局差异显著时,TVDI模型反演精度会受到地表温度(Ts)等因素的影响.被动微波AMSR-E数据精确记录了像元内的土壤水分信息,但空间分辨率低.本文利用同时期的MODIS与被动微波数据,发展了针对青藏高原地区高精度土壤水分反演算法.首先,在TVDI模型中,利用修正型土壤调整植被指数(MSAVI)代替归一化植被指数(NDVI),以改进NDVI易饱和的缺点;其次,利用ASTER GDEM数据,对地形高程和纬度差异引起的地表温度变化进行了校正;然后,通过神经网络训练建立基于TVDI、被动微波以及辅助气象数据的土壤水分反演模型,并应用该模型反演了青藏高原地区三个观测网(CAMP/Tibet、玛曲和那曲)的土壤水分;最后,利用实测土壤水分数据对反演结果进行验证,结果表明该模型的精度均方根误差(RMSE)数值可达到0.031~0.041 m~3·m~(-3).本文还应用该算法反演了青藏高原连续的土壤水分的空间分布,并比较了土壤水分的变化趋势与实测降水变化趋势,结果表明二者变化量的正负关系一致. 相似文献
11.
Groundwater temperature is an important water quality parameter that affects species distributions in subsurface and surface environments. To investigate the response of subsurface temperature to atmospheric climate change, an analytical solution is derived for a one‐dimensional, transient conduction–advection equation and verified with numerical methods using the finite element code SUTRA. The solution can be directly applied to forward model the impact of future climate change on subsurface temperature profiles or inversely applied to produce a surface temperature history from measured borehole profiles. The initial conditions are represented using superimposed linear and exponential functions, and the boundary condition is expressed as an exponential function. This solution expands on a classic solution in which the initial and boundary conditions were restricted to linear functions. The exponential functions allow more flexibility in matching climate model projections (boundary conditions) and measured temperature–depth profiles (initial conditions). For example, measured borehole temperature data from the Sendai Plain and Tokyo, Japan, were used to demonstrate the improved accuracy of the exponential function for replicating temperature–depth profiles. Also, the improved accuracy of the exponential boundary condition was demonstrated using air temperature anomaly data from the Intergovernmental Panel on Climate Change. These air temperature anomalies were then used to forward model the effect of surficial thermal perturbations in subsurface environments with significant groundwater flow. The simulation results indicate that recharge can accelerate shallow subsurface warming, whereas upward groundwater discharge can enhance deeper subsurface warming. Additionally, the simulation results demonstrate that future groundwater temperatures obtained from the proposed analytical solution can deviate significantly from those produced with the classic solution. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
12.
We estimated the effects of hydrogeological and surface temperature warming on subsurface thermal regime from the temperature-depth profiles and hydrological data of groundwater quality both in the quaternary and tertiary systems in the Sendai Plain as a preliminary step toward reconstruction of climate changes.Annual mean air temperature in the plain has increased about 1.5 °C in the last 70 years and this surface warming resulted in low or negative thermal gradient. However, anomaly of thermal gradient was recognized in not all temperature-depth profiles. Groundwater chemical compositions and stable isotope data (δD and δ18O) show that the groundwater flow system has marked difference between those of tertiary and quaternary systems. Calculated results of three dimensional groundwater flow and heat transport model ensure the above hypothesis and shows that thermal gradient changes at close to basement of the quaternary system. The differences in groundwater flow systems are expressed as subsurface thermal gradient anomalies in the temperature-depth profiles in the Sendai Plain. Furthermore, one-dimensional numerical analyze including the effect of surface warming indicates that calculated profile has departure from steady state line at depths in 60-80 m agree well with observed one. 相似文献
13.
Aufeis (also known as icings) are large sheet-like masses of layered ice that form in river channels in arctic environments in the winter as groundwater discharges to the land surface and subsequently freezes. Aufeis are important sources of water for Arctic river ecosystems, bolstering late summer river discharge and providing habitat for caribou escaping insect harassment. The aim of this research is to use numerical simulations to evaluate a conceptual model of subsurface hydrogeothermal conditions that can lead to the formation of aufeis. We used a conceptual model based on geophysical data from the Kuparuk aufeis field on the North Slope of Alaska to develop a two-dimensional heterogeneous vertical profile model of groundwater flow, heat transport, and freeze/thaw dynamics. Modelling results showed that groundwater can flow to the land surface through subvertical high permeability pathways during winter months when the lower permeability soils near the land surface are frozen. The groundwater discharge can freeze on the surface, contributing to aufeis formation throughout the winter. We performed sensitivity analyses on subsurface properties and surface temperature and found that aufeis formation is most sensitive to the volume of unfrozen water available in the subsurface and the rate at which the subsurface water travels to the land surface. Although a trend of warming air temperatures will lead to a greater volume of unfrozen subsurface water, the aufeis volume can be reduced under warming conditions if the period of time for which air temperatures are below freezing is reduced. 相似文献
14.
Detailed monitoring of surface atmospheric and subterranean microclimatic conditions has provided a new opportunity to interpret drip water temperature changes associated with climate variability. High-resolution multi-index monitoring was conducted in Xiaoyan Cave, Guilin, southwest China, for a period of four years (2011–2014) to identify the processes that control drip water temperature. The results show that variations in drip water temperature are mainly coupled to changes in the cave air temperature unless large drip discharge occurs. The controls on cave air temperature depend on the ventilation modes that eventually affect drip water. The multiple thermal mechanisms are winter ventilation, heat conduction in summer and water flow-induced convection derived from subsurface water percolation into the cave due to fast preferential flow during heavy rain events. Drip water response to extreme temperature anomalies is shown to be sensitive to outside climate. 相似文献
15.
The effects of climatic variability on estimates of recharge from temperature profiles 总被引：1，自引：0，他引：1
Using heat as a tracer allows for estimation of ground water recharge rates based on subsurface temperature measurements. While possible in theory, it may be difficult in practice to discriminate the effects of climate from the effects of ground water advection. This study uses synthetic simulations to determine the influence of variability of ground surface temperature (GST) on the ability to estimate vertical specific discharge from temperature profiles. Results suggest that in cases where temperature measurements are sufficiently deep and specific discharge is sufficiently high, estimates of specific discharges will be reasonably accurate. Increasing the number of times temperatures are measured, or producing models that incorporate variations in GST, will increase the reliability of any studies using temperatures to estimate specific discharge. Furthermore, inversions of temperature measurements should be combined with other methods of estimating recharge rates to improve the reliability of recharge estimates. 相似文献
16.
V. Čermák J. Šafanda L. Bodri M. Yamano E. Gordeev 《Studia Geophysica et Geodaetica》2006,50(4):675-695
To reconstruct the recent climate history in Kamchatka, a series of repeated precise temperature logs were performed in a
number of boreholes located in a broad east-west strip (between 52 and 54°N) in the central part of Kamchatka west of Petropavlovsk-Kamchatski.
Within three years more than 30 temperature logs were performed in 10 holes (one up to six logs per hole) to the depth of
up to 400 metres. Measured temperature gradients varied in a broad interval 0 to 60 mK/m and in some holes a sizeable variation
in the subsurface temperatures due to advective heat transport by underground water was observed. Measured data were compared
with older temperature profiles obtained in the early eighties by Sugrobov and Yanovsky (1993). Even when older data are of
poorer precision (accuracy of about 0.1 K), they presented valuable information of the subsurface temperature conditions existing
20–25 years ago. Borehole observations and the inverted ground surface temperature histories (GSTHs) used for the paleoclimate
reconstruction were complemented with a detailed survey of meteorological data. Namely, the long-term surface air temperature
(SAT) and precipitation records from Petropavlovsk station (in operation since 1890) were used together with similar data
from a number of local subsidiary meteo-stations operating in Central Kamchatka since 1950. Regardless of extreme complexity
of the local meteorological/climate conditions, diversity of borehole sites and calibration of measuring devices used during
the whole campaign, the results of the climate reconstruction supported a general warming of about 1 K characteristic for
the 20th century, which followed an inexpressive cooler period typical for the most of the 19th century. In the last three
to four decades the warming rate has been locally increasing up to 0.02 K/year. It was also shown that the snow cover played
a dominant role in the penetration of the climate “signal” to depth and could considerably smooth down the subsurface response
to the changes occurred on the surface. 相似文献
17.
G. Palmason 《Bulletin of Volcanology》1969,33(1):243-243
Data on subsurface temperature conditions from borehole measurements in various parts of Iceland were presented. The subsurface temperature field is in many areas found to be controlled by the movement of water in the upper part of the crust, and so is also the surface heat flow by conduction. Data were presented to show that conditions for free convection of water may well exist in the neovolcanic zone of Iceland. It is suggested that this phenomenon may account for the anomalous heat flow pattern observed on the Mid-Atlantic Ridge. For a more detailed account of this paper the reader is referred to the following: Gudmar Pálmason, 1967,On heat flow in Iceland in relation to the Mid-Atlantic Ridge. In:Iceland and mid-ocean ridges (Ed.S. Björnsson), Vis. Isl. (Societas Scientiarum Islandica), Reykjavik. 相似文献
18.
Use of shallow groundwater temperature profiles to infer climate and land use change: interpretation and measurement challenges 
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下载免费PDF全文 Temperature is often used to infer the effect of land use and climate conditions on aquifers. Reliable data are needed to examine the temperature behaviour in the subsurface; thus, the use of robust acquisition techniques is unavoidable. Three temperature measurement techniques were applied to assess the sources of bias that could occur during temperature logging in a shallow Quaternary coastal aquifer in Ferrara (Northern Italy). Open borehole temperature logging, multilevel sampling straddle packers isolated temperature measurements within a flow cell above ground and multilevel sampling straddle packers isolated temperature measurements via an in‐well level logger (MLS‐IW) were compared for several coastal monitoring wells to gain insights on the limitations of each technique. Results show that the source of bias between the three applied techniques are different: (i) the open borehole temperature logging method tends to record heat convection through the open borehole and is not representative of the aquifer temperature distribution; (ii) the multilevel sampling straddle packers isolated temperature measurements within a flow cell above ground method is swayed by the air temperature and the heating of the submersible pump used to lift groundwater above ground; and (iii) the MLS‐IW provides the most reliable vertical thermal profiling both in summer and winter, because groundwater temperature is directly measured at the selected monitoring depth. The implementation of a 1D flow model demonstrates that if precise temperature profiles are needed to infer the influence that land use and climate changes have on groundwater, the MLS‐IW method is a reliable method that could be applied to existing monitoring wells. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
19.
A numerical method is used to investigate the effect of topographic and local thermal conductivity anomalies on near-surface heat flow for two-dimensional models. Heat flow associated with a sloping topographic structure is calculated. Also, the effects of a fault structure associated with the sloping topography are considered. Vertical and horizontal heat flow components are calculated alone; the surface of the earth as well as throughout the whole region of interest. The results indicate that surface heat flow is substantially affected by topographic relief and the horizontal heat flow component associated with topographic features can be large. Also, regional heat flow is greatly perturbed by local thermal conductivity anomalies and the effect of topographic features may be considerably modified by the subsurface structure. 相似文献
20.
The potential impact of climate change on water resources has been intensively studied for different regions and climates across the world. In regions where winter processes such as snowfall and melting play a significant role, anticipated changes in temperature might significantly affect hydrological systems. To address this impact, modifications have been made to the fully integrated surface-subsurface flow model HydroGeoSphere (HGS) to allow the simulation of snow accumulation and melting. The modified HGS model was used to assess the potential impact of climate change on surface and subsurface flow in the Saint-Charles River catchment, Quebec (Canada) for the period 2070 to 2100. The model was first developed and calibrated to reproduce observed streamflow and hydraulic heads for current climate conditions. The calibrated model was then used with three different climate scenarios to simulate surface flow and groundwater dynamics for the 2070 to 2100 period. Winter stream discharges are predicted to increase by about 80, 120, and 150% for the three scenarios due to warmer winters, leading to more liquid precipitation and more snowmelt. Conversely, the summer stream discharges are predicted to fall by about 10, 15, and 20% due to an increase in evapotranspiration. However, the annual mean stream discharge should remain stable (±0.1 m3/s). The predicted increase in hydraulic heads in winter may reach 15 m and the maximum decrease in summer may reach 3 m. Simulations show that winter processes play a key role in the seasonal modifications anticipated for surface and subsurface flow dynamics. 相似文献