作者：
Zou, Bin;Wilson, J. Gaines;Zhan, F. Benjamin;Zeng, Yongnian
期刊：
Journal of environmental monitoring : JEM,2009年11(3):475-490 ISSN：1464-0325
通讯作者：
Zou, B
作者机构：
[Zhan, F. Benjamin; Zou, Bin] Texas State Univ, Texas Ctr Geog Informat Sci, Dept Geog, San Marcos, TX 78666 USA.;[Zhan, F. Benjamin] Wuhan Univ, Sch Resource & Environm Sci, Wuhan 430079, Hubei, Peoples R China.;[Zou, Bin; Zeng, Yongnian] Cent S Univ, Sch Infophys & Geomat Engn, Changsha 410086, Hunan, Peoples R China.;[Wilson, J. Gaines] Univ Texas Brownsville, Dept Chem & Environm Sci, Brownsville, TX 78520 USA.
通讯机构：
[Zou, Bin] Cent S Univ, Sch Infophys & Geomat Engn, Changsha 410086, Hunan, Peoples R China.
摘要：
The assessment of personal exposure to air pollution is a critical component of epidemiological studies associating air pollution and health effects. This paper critically reviewed 157 studies over 29 years that utilized one of five categories of exposure methods (proximity, air dispersion, hybrid, human inhalation, and biomarkers). Proximity models were found to be a questionable technique as they assume that closer proximity equates to greater exposure. Inhalation models and biomarker estimates were the most effective in assessing personal exposure, but are often cost prohibitive for large study populations. This review suggests that: (i) factors such as uncertainty, validity, data availability, and transferability related to exposure assessment methods should be considered when selecting a model; and (ii) although an entirely discreet new class of approach is not necessary, significant progress could be made through the development of a 'hybrid' model utilizing the strengths of several existing methods. Future work should systematically evaluate the performance of hybrid models compared to other individual exposure assessment methods utilizing geospatial information technologies (e.g. geographic information systems (GIS) and remote sensing (RS)) to more robustly refine estimates of ambient exposure and quantify the linkages and differences between outdoor, indoor and personal exposure estimates.
作者机构：
[Geng, Jianzhen; Hao, Shuang; Li, Huimin] Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China;[Peng, Jiantang; Zhang, Dongliang] School of Geoscience and Info-physics, Central South University, Changsha 410083, China;[Yuan, Shunda; Peng, Jiantang; Zhang, Dongliang] State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, CAS, Guiyang 550002, China;[Yuan, Shunda] MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, CAGS, Beijing 100037, China;[Yuan, Shunda] State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
通讯机构：
[Yuan, Shunda] CAGS, Inst Mineral Resources, MLR Key Lab Metallogeny & Mineral Assessment, Beijing 100037, Peoples R China.
关键词：
Age constraints - Cassiterite - Confidence levels - Hunan province - Hunan province , China - ID-TIMS - In-situ - Isochron age - LA-MC-ICP-MS - South China - U-Pb ages - U-Pb dating - U-Pb geochronology - Weighted mean
作者：
Zhao, Chongbin;Hobbs, B. E.;Hornby, P.;Ord, A.;Peng, Shenglin;Liu, Liangming
期刊：
International Journal for Numerical and Analytical Methods in Geomechanics,2008年32(9):1107-1130 ISSN：1096-9853
通讯作者：
Zhao, CB
作者机构：
[Ord, A.; Hobbs, B. E.; Hornby, P.; Zhao, Chongbin] CSIRO Division of Exploration and Mining, P.O. Box 1130, Bentley, WA 6102, Australia;[Peng, Shenglin; Zhao, Chongbin; Liu, Liangming] Computational Geosciences Research Centre, Central South University, Changsha 410083, China
通讯机构：
[Zhao, Chongbin] Cent S Univ, Computat Geosci Res Ctr, Changsha 410083, Peoples R China.
关键词：
chemical‐dissolution;front propagation;porosity feedback effect;reactive transport;numerical simulation;porous media
作者机构：
[Changsheng Cai] Department of Surveying and Geo-informatics, Central South University, Changsha, 410083, China;[Yang Gao] Department of Geomatics Engineering, University of Calgary, Calgary, T2N 1N4, Canada;[Yang Gao] School of Geomatics, Liaoning Technical University, Fuxin, 123000, China
摘要：
A combination of GPS and GLONASS observations can offer improved reliability, availability and accuracy for precise point positioning (PPP). We present and analyze a combined GPS/GLONASS PPP model, including both functional and stochastic components. Numerical comparison and analysis are conducted with respect to PPP based on only GPS or GLONASS observations to demonstrate the benefits of the combined GPS/GLONASS PPP. The observation residuals are analyzed for more appropriate stochastic modeling for observations from different navigation systems. An analysis is also made using different precise orbit and clock products. The performance of the combined GPS/GLONASS PPP is assessed using both static and kinematic data. The results indicate that the convergence time can be significantly reduced with the addition of GLONASS data. The positioning accuracy, however, is not significantly improved by adding GLONASS data if there is a sufficient number of GPS satellites with good geometry.
作者：
Hu Jun;Li ZhiWei;Zhu JianJun;Ren XiaoChong;Ding XiaoLi
期刊：
Science China Earth Sciences,2010年53(4):550-560 ISSN：1674-7313
通讯作者：
Li, ZW
作者机构：
[Ren XiaoChong; Hu Jun; Li ZhiWei; Zhu JianJun] Department of Survey Engineering and Geomatics, Central South University, Changsha 410083, China;[Ding XiaoLi] Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong, China
通讯机构：
[Li ZhiWei] Cent S Univ, Dept Survey Engn & Geomat, Changsha 410083, Hunan, Peoples R China.
关键词：
3-D displacement - 3D surface - Amplitude information - Amplitude matching - Azimuth direction - Bam earthquake - Displacement field - Ground surfaces - Horizontal movements - Interferometric phase - Interferometric phasis - Interferometric synthetic aperture radars - Line-of-sight - Method of least squares - Surface displacement - Three-dimensional (3D) surfaces - Three-dimensional surface - Variance component estimation
摘要：
Conventional Interferometric Synthetic Aperture Radar (InSAR) technology can only measure one-dimensional surface displacement (along the radar line-of-sight (LOS) direction). Here we presents a method to infer three-dimensional surface displacement field by combining SAR interferometric phase and amplitude information of ascending and descending orbits. The method is realized in three steps: (1) measuring surface displacements along the LOS directions of both ascending and descending orbits based on interferometric phases; (2) measuring surface displacements along the azimuth directions of both the ascending and descending orbits based on the SAR amplitude data; and (3) estimating the three-dimensional (3D) surface displacement field by combining the above four independent one-dimensional displacements using the method of least squares and Helmert variance component estimation. We apply the method to infer the 3D surface displacement field caused by the 2003 Bam, Iran, earthquake. The results reveal that in the northern part of Bam the ground surface experienced both subsidence and southwestward horizontal movement, while in the southern part uplift and southeastward horizontal movement occurred. The displacement field thus determined matches the location of the fault very well with the maximal displacements reaching 22, 40, and 30 cm, respectively in the up, northing and easting directions. Finally, we compare the 3D displacement field with that simulated from the Okada model. The results demonstrate that the method presented here can be used to generate reliable and highly accurate 3D surface displacement fields.
作者：
Zhao, Chongbin;Hobbs, B. E.;Ord, A.;Hornby, P.;Peng, Shenglin
期刊：
Geofluids,2008年8(2):113-127 ISSN：1468-8123
通讯作者：
Zhao, CB
作者机构：
[Peng, Shenglin; Zhao, Chongbin] Cent S Univ, Computat Geosci Res Ctr, Changsha 410083, Peoples R China.;[Hornby, P.; Hobbs, B. E.; Ord, A.] CSIRO, Div Explorat & Min, Bentley, WA, Australia.
通讯机构：
[Zhao, Chongbin] Cent S Univ, Computat Geosci Res Ctr, Changsha 410083, Peoples R China.
关键词：
chemical dissolution;chemical dissolution front instability;front propagation;numerical simulation;porous media;three‐dimensional problem
摘要：
This paper is concerned with the morphological evolution of three‐dimensional chemical dissolution fronts that occur in fluid‐saturated porous media. A fully coupled system between porosity, pore‐fluid flow and reactive chemical species transport is considered to describe this phenomenon. Using the newly presented concept of the generalized dimensionless pore fluid pressure‐gradient, which can be used to represent the interaction between solute advection, solute diffusion, chemical kinetics and the shape factor of the soluble mineral, a theoretical criterion has been established to assess the likelihood of instability at a chemical dissolution front in the reactive transport system. To simulate the chemical dissolution front evolution in a three‐dimensional fluid‐saturated porous medium, a numerical procedure combining both the finite difference method and the finite element method has been proposed. As the problem belongs to a complex system science problem, a small randomly generated perturbation of porosity is added to the initial porosity of a three‐dimensional homogeneous domain to trigger instability of a planar chemical dissolution front during its propagation within the fluid‐saturated porous medium. To test the correctness and accuracy of the proposed numerical procedure, a three‐dimensional benchmark problem has been constructed and the related analytical solution has been derived. This enables using the proposed numerical procedure for simulating the morphological evolution of a three‐dimensional chemical dissolution front from a stable, planar state into an unstable, fingering state. The related numerical results demonstrate that the proposed numerical procedure is useful for, and capable of, simulating the morphological instability of a three‐dimensional chemical dissolution front within a fluid‐saturated porous medium.
期刊：
International Journal of Geographical Information Science,2012年26(6):1073-1089 ISSN：1365-8816
通讯作者：
Zou, Bin
作者机构：
[Neng Wan] Department of Health Services Research & Administration , University of Nebraska Medical Center , Omaha , NE , USA;[Bin Zou] Department of Survey Engineering and Geomatics, School of Geosciences and Info-physics , Central South University , Changsha , China;[Troy Sternberg] School of Geography and Environment , Oxford University , Oxford , UK
通讯机构：
[Zou, Bin] Cent S Univ, Dept Survey Engn & Geomat, Sch Geosci & Infophys, Changsha, Peoples R China.;Department of Survey Engineering and Geomatics, School of Geosciences and Info-physics , Central South University , Changsha , China
关键词：
spatial access;health professional shortage area;health service;GIS;E2SFCA;Gravity model
摘要：
Gravity-based spatial access models have been widely used to estimate spatial access to healthcare services in an attempt to capture the interaction of various factors. However, these models are inadequate in informing health resource allocation work due to their inappropriate assumption of healthcare demand. For the purpose of effective healthcare resource planning, this article proposes a three-step floating catchment area (3SFCA) method to minimize the healthcare-demand overestimation problem. Specifically, a spatial impedance-based competition scheme is incorporated into the enhanced two-step floating catchment area (E2SFCA) method to account for a reasonable model of healthcare supply and demand. A case study of spatial access to primary care physicians along the Austin–San Antonio corridor area in central Texas showed that the proposed method effectively minimizes the overestimation of healthcare demand and reflects a more balanced geographic pattern of spatial access than E2SFCA. In addition, by using an adjusted spatial access index, the 3SFCA method indicates strong potential for identifying health professional shortage areas. The study concludes that 3SFCA is a promising method to provide health professionals and decision makers with useful healthcare accessibility information.
摘要：
Interferometric Synthetic Aperture Radar (InSAR) is a powerful technology for observing the Earth surface, especially for mapping the Earth's topography and deformations. InSAR measurements are however often significantly affected by the atmosphere as the radar signals propagate through the atmosphere whose state varies both in space and in time. Great efforts have been made in recent years to better understand the properties of the atmospheric effects and to develop methods for mitigating the effects. This paper provides a systematic review of the work carried out in this area. The basic principles of atmospheric effects on repeat-pass InSAR are first introduced. The studies on the properties of the atmospheric effects, including the magnitudes of the effects determined in the various parts of the world, the spectra of the atmospheric effects, the isotropic properties and the statistical distributions of the effects, are then discussed. The various methods developed for mitigating the atmospheric effects are then reviewed, including the methods that are based on PSInSAR processing, the methods that are based on interferogram modeling, and those that are based on external data such as GPS observations, ground meteorological data, and satellite data including those from the MODIS and MERIS. Two examples that use MODIS and MERIS data respectively to calibrate atmospheric effects on InSAR are also given.
作者机构：
[Zhao, Yu; Hu, Mao-Gui; Wang, Jin-Feng; Xu, Cheng-Dong] Chinese Acad Sci, Inst Geog Sci & Nat Resources Res, State Key Lab Resources & Environm Informat Syst, Beijing, Peoples R China.;[Zhao, Yu] Cent S Univ, Sch Geosci & Infophys, Changsha, Hunan, Peoples R China.;[Christakos, George] San Diego State Univ, Dept Geog, San Diego, CA 92182 USA.
通讯机构：
[Wang, Jin-Feng] Chinese Acad Sci, Inst Geog Sci & Nat Resources Res, State Key Lab Resources & Environm Informat Syst, Beijing, Peoples R China.
摘要：
There has been discrepancies between the daily air quality reports of the Beijing municipal government, observations recorded at the U.S. Embassy in Beijing, and Beijing residents' perceptions of air quality. This study estimates Beijing's daily area PM(2.5) mass concentration by means of a novel technique SPA (Single Point Areal Estimation) that uses data from the single PM(2.5) observation station of the U.S Embassy and the 18 PM(10) observation stations of the Beijing Municipal Environmental Protection Bureau. The proposed technique accounts for empirical relationships between different types of observations, and generates best linear unbiased pollution estimates (in a statistical sense). The technique extends the daily PM(2.5) mass concentrations obtained at a single station (U.S. Embassy) to a citywide scale using physical relations between pollutant concentrations at the embassy PM(2.5) monitoring station and at the 18 official PM(10) stations that are evenly distributed across the city. Insight about the technique's spatial estimation accuracy (uncertainty) is gained by means of theoretical considerations and numerical validations involving real data. The technique was used to study citywide PM(2.5) pollution during the 423-day period of interest (May 10, 2010 to December 6, 2011). Finally, a freely downloadable software library is provided that performs all relevant calculations of pollution estimation.
期刊：
IEEE GEOSCIENCE AND REMOTE SENSING LETTERS,2013年10(3):495-499 ISSN：1545-598X
通讯作者：
Qi, SX
作者机构：
[Ma, Jie; Qi, Shengxiang; Tian, Jinwen; Yang, Changcai] Institute for Pattern Recognition and Artificial Intelligence, Huazhong University of Science and Technology, Wuhan, 430074, China;[Tao, Chao] School of Geosciences and Info-Physics, Central South University, Changsha, 410083, China
期刊：
Journal of Power Sources,2013年234:197-200 ISSN：0378-7753
通讯作者：
Chen, QQ
作者机构：
[Zhang, Tingting; Chen, Quanqi; Qiao, Xiaochang] School of Chemistry, Xiangtan University, Xiangtan 411105, China;[Chen, Quanqi; Yang, Jianwen] College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China;[Li, Diquan] School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
作者机构：
[Xiaoqing Deng] Department of Information, Hunan Business College, Changsha 410205, China;[Gong Cheng] School of Geosciences and Environment Engineering, Central South University, Changsha 410083, China
通讯机构：
[Deng, Xiaoqing] Hunan Business Coll, Dept Informat, Changsha 410205, Hunan, Peoples R China.
关键词：
Critical point theory - Discrete Hamiltonian systems - Homoclinic orbits - Second order discrete Hamiltonian systems - Second orders - Sufficient conditions
摘要：
In this paper, a class of second order discrete Hamiltonian systems without any periodicity assumptions are considered. Base on the critical point theory, some sufficient conditions for the existence of homoclinic orbits are obtained. The results obtained extend the results in [2006] by relaxing the assumptions on the sign of the potential.
作者机构：
[Ding, X. L.; Zhang, L.] Hong Kong Polytech Univ, Dept Land Surveying & Geoinformat, Kowloon, Hong Kong, Peoples R China.;[Li, Z. W.; Sun, Q.; Hu, J.; Zhu, J. J.] Cent S Univ, Sch Geosci & Infophys, Changsha 410083, Hunan, Peoples R China.
通讯机构：
[Li, Z. W.] Cent S Univ, Sch Geosci & Infophys, Changsha 410083, Hunan, Peoples R China.
摘要：
One-dimensional measurement along the Line-Of-Sight (LOS) direction has greatly limited the capability of InSAR technique in the investigation of surface displacements and their dynamics. In recent years, great efforts have been made to resolve complete three-dimensional (3-D) displacements from InSAR measurements. This contribution is intended to provide a systematic review of the progress achieved in this field. Based on an analysis of the InSAR LOS measurements, we first cover two commonly used techniques, i.e., Offset-Tracking and multi-aperture InSAR (MAI), with which the surface displacement in the azimuth direction can be measured together with the LOS displacement. Several methods for mapping 3-D displacements using InSAR measurements are subsequently presented and categorized into three groups: (i) combination of multi-pass LOS and azimuth measurements; (ii) integration of InSAR and GPS data; and (iii) prior information assisted approaches. The strengths and weaknesses of each method are analyzed to show the applicability of each method to specific 3-D displacement mapping cases, in hope to provide a useful guidance in choosing a suitable approach accordingly. Finally, suggestions for resolving the challenging issues and outlook of future research are given. (c) 2014 Elsevier B.V. All rights reserved.
作者：
Feng, GuangCai;Hetland, Eric A.;Ding, XiaoLi;Li, ZhiWei;Zhang, Lei
期刊：
Geophysical Research Letters,2010年37(1):- ISSN：0094-8276
通讯作者：
Feng, GC
作者机构：
[Zhang, Lei; Feng, GuangCai; Ding, XiaoLi] Department of Land Surveying and Geo-Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong;[Hetland, Eric A.] Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, United States;[Li, ZhiWei] Department of Geomatics, Central South University, Changsha 410083, China
通讯机构：
[Feng, GuangCai] Hong Kong Polytech Univ, Dept Land Surveying & Geoinformat, Kowloon, Hong Kong, Peoples R China.
摘要：
We infer co-seismic fault slip during the 2008 M-w 7.9 Wenchuan earthquake from interferometric synthetic aperture radar (InSAR) and GPS observations of ground deformation. We use ALOS/PALSAR data from ascending orbits on six tracks, and we do not use data that are strongly affected by ionospheric perturbations. We use a fault model composed of three planar fault segments of the Beichuan fault, and one planar segment representing the parallel Pengguan fault. Maximum thrust-slip is up to 6.7 m near the surface, and occurs in two locations, near Yingxiu in the south and Beichuan in the center of the rupture. Maximum strike-slip is over 4 m, and occurs near Pingtong and Nanba along the northern end of the rupture. We find that the ratio of coseismic thrust-to strike-slip on the Beichuan fault decreases from 1.5 to 0.7 from the SW to the NE. Citation: Feng, G., E. A. Hetland, X. Ding, Z. Li, and L. Zhang (2010), Coseismic fault slip of the 2008 Mw 7.9 Wenchuan earthquake estimated from InSAR and GPS measurements, Geophys. Res. Lett., 37, L01302, doi:10.1029/2009GL041213.
期刊：
International Journal for Numerical and Analytical Methods in Geomechanics,2010年34(17):1767-1796 ISSN：1096-9853
通讯作者：
Zhao, C.(chongbin.zhao@iinet.net.au)
作者机构：
[Ord, A.; Hobbs, B. E.] CSIRO Division of Exploration and Mining, P. O. Box 1130, Bentley, WA 6102, Australia;[Ord, A.; Hobbs, B. E.] School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;[Zhao, Chongbin] Computational Geosciences Research Centre, Central South University, Changsha 410083, China;Computational Geosciences Research Centre, Central South University, Changsha 410083, People's Republic of China
通讯机构：
[Zhao, Chongbin] Cent S Univ, Computat Geosci Res Ctr, Changsha 410083, Peoples R China.
关键词：
nonaqueous phase liquid;residual saturation;NAPL dissolution;front instability;reactive mass transport;porous media
作者机构：
[Qian Zhao, Yu; Hong Wang, Xiao] School of Geosciences and Info-physics, Central South University, Changsha, Hunan 410083, China;[Shih, Frank Y.] College of Computing Sciences, New Jersey Institute of Technology, Newark, NJ 07102, United States;[Fang Wang, Xiao] Ecole Centrale de Lyon, ICJ, UMR5205, F-69134, France
通讯机构：
[Zhao, Yu Qian] Cent S Univ, Sch Geosci & Infophys, Changsha 410083, Hunan, Peoples R China.
期刊：
EARTH AND PLANETARY SCIENCE LETTERS,2012年349:186-197 ISSN：0012-821X
通讯作者：
Sun, Y
作者机构：
[Chen, Youlin] Array Information Technology, Greenbelt, MD, United States;[Sun, Ya; Liu, Jianxin] School of Geosciences and Info-Physics, Central South University, Changsha, China;[Sun, Ya; Liu, Huafeng; Niu, Fenglin] Department of Earth Science, Rice University, Houston, TX, United States
通讯机构：
[Sun, Ya] Cent S Univ, Sch Geosci & Infophys, Changsha, Hunan, Peoples R China.
摘要：
We analyze a large amount of receiver function data recorded by regional seismic networks of the China Earthquake Administration to estimate crustal structure and deformation beneath the southeast margin of the Tibetan plateau and its surrounding areas. We develop a comprehensive analysis method that facilitates robust extraction of azimuthal seismic anisotropy from receiver function data. The method includes an estimate of fast polarization direction and splitting time by a joint analysis of radial and transverse receiver function data, and an evaluation of measurement reliability by statistical and harmonic analysis. We find significant seismic anisotropy with a splitting time of 0.5-0.9 s beneath the SE margin of the Tibetan plateau. Both the splitting time and fast polarization direction are comparable to those estimated from SKS/SKKS data, suggesting that crustal anisotropy is the main cause of shear wave splitting of the SKS/SKKS wave. This also suggests that deformation in the upper mantle is either weak or predominantly vertical, and is obviously different from the one in the crust. A vertical flow in the upper mantle, combined with the observation of a thin lithosphere beneath the study area, leads to the inference that part of the mantle lithosphere may have been removed and is descending into deep mantle. Stations located in the surrounding areas, on the other hand, exhibit very little to no crustal anisotropy. The estimated Moho depth and Vp/Vs ratio also show a distinct difference between the SE Tibetan plateau and the surrounding regions. Stations on the Tibetan plateau have a Vp/Vs ratio of similar to 1.79, which is substantially higher than those measured at the Yunnan-Guizhou (Yungui) plateau (similar to 1.69). Our observations here are consistent with the scenario that the SE Tibet has been built by lower crustal flow. They also suggest that the mantle lithosphere beneath the margin may have been mechanically decoupled from the upper crust. (C) 2012 Elsevier B.V. All rights reserved.
期刊：
ISPRS Journal of Photogrammetry and Remote Sensing,2008年63(6):621-634 ISSN：0924-2716
通讯作者：
Ding, X.L.(lsxlding@polyu.edu.hk)
作者机构：
[Li, Z.W.; Huang, C.; Chen, Y.L.; Ding, X.L.] Department of Land Surveying and Geo-informatics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, Hong Kong;[Li, Z.W.; Zhu, J.J.] School of Info-Physics and Geomatics Engineering, Central South University, Changsha, 410083 Hunan, China
通讯机构：
[Ding, X.] Hong Kong Polytech Univ, Dept Land Surveying & Geoinformat, Kowloon, Hong Kong, Peoples R China.
关键词：
Synthetic aperture radar (SAR);Modified Goldstein filter;Phase filtering;Coherence;Look number
摘要：
Phase noise in a radar interferogram is directly related to interferometric coherence and the look number of the interferogram. Therefore an optimal radar interferogram filter should incorporate information on both interferometric coherence and look number. We present a modification to the commonly used Goldstein filter by Suggesting an improved determination of the filtering parameter. Experimental results with both simulated and real data sets show that the new filter offers much better results when used to filter radar interferograms. (C) 2008 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS). Published by Elsevier B.V. All rights reserved.
摘要：
The usefulness of gravity-based spatial access models is limited because of the uncertainty introduced by the range of values of the impedance coefficient. To solve this problem, this paper proposes the concept of spatial access ratio (SPAR) derived from the enhanced 2-step floating catchment area (E2SFCA) method - a recent extension of the gravity model - to assess potential spatial access. First, a sensitivity assessment is conducted to verify the effectiveness of SPAR and its advantages in overcoming the uncertainty problem. Then, the E2SFCA method and the shortest travel time method are employed to measure potential spatial access to colorectal cancer (CRC) prevention and treatment services in Texas based on data at the census tract level. The socio-demographic and geographic distributions of potential spatial access to CRC services are also examined. The sensitivity assessment reveals substantial fluctuations in the values of the spatial access index calculated directly by the E2SFCA method under different values of the impedance coefficient. However, the values of SPAR remain stable under different values of the coefficient. A comparative analysis indicates that potential spatial access to primary care physicians (PCPs), CRC screening facilities, and oncologists varied among different racial/ethnic and socioeconomic population groups as well as in different geographic regions in Texas. Non-Hispanic blacks, Asians, and people in affluent areas had a geographical advantage in accessing CRC services than other groups. The urban/rural difference was more obvious and serious than those of different racial/ethnic groups and groups with different socio-economic statuses, as metropolitan residents had more than three times the potential spatial access than isolated rural residents. (C) 2011 Elsevier Ltd. All rights reserved.
作者机构：
[Feng, Guangcai; Zhu, Jianjun; Li, Zhiwei] Cent S Univ, Sch Geosci & Infophys, Lab Radar Remote Sensing, Changsha 410083, Hunan, Peoples R China.;[Shan, Xinjian; Zhang, Guohong] China Earthquake Adm, Inst Geol, State Key Lab Earthquake Dynam, Beijing 100029, Peoples R China.;[Zhang, Lei] Hong Kong Polytech Univ, Dept Land Surveying & Geoinformat, Kowloon, Hong Kong, Peoples R China.
通讯机构：
[Li, Zhiwei] Cent S Univ, Sch Geosci & Infophys, Lab Radar Remote Sensing, Changsha 410083, Hunan, Peoples R China.
关键词：
Satellite geodesy;Radar interferometry;Earthquake source observations;Seismicity and tectonics
摘要：
We map the complete surface deformation of 2015 M-w 7.8 Gorkha Nepal earthquake and its M-w 7.3 aftershock with two parallel ALOS2 descending ScanSAR paths' and two ascending Stripmap paths' images. The coseismic fault-slip model from a combined inversion of InSAR and GPS data reveals that this event is a reverse fault motion, with a slight right-lateral strike-slip component. The maximum thrust-slip and right-lateral strike-slip values are 5.7 and 1.2 m, respectively, located at a depth of 7-15 km, southeast to the epicentre. The total seismic moment 7.55 x 10(20) Nm, corresponding to a moment magnitude M-w 7.89, is similar to the seismological estimates. Fault slips of both the main shock and the largest aftershock are absent from the upper thrust shallower than 7 km, indicating that there is a locking lower edge of Himalayan Main Frontal Thrust and future seismic disaster is not unexpected in this area. We also find that the energy released in this earthquake is much less than the accumulated moment deficit over the past seven centuries estimated in previous studies, so the region surrounding Kathmandu is still under the threaten of seismic hazards.
