Validation and comparison of Advanced Differential Interferometry Techniques: Murcia metropolitan area case study   总被引：1，自引：0，他引：1  

G. Herrera  R. Toms  J.M. Lopez-Sanchez  J. Delgado  F. Vicente  J. Mulas  G. Cooksley  M. Sanchez  J. Duro  A. Arnaud  P. Blanco  S. Duque  J.J. Mallorqui  R. De la Vega-Panizo  O. Monserrat 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(5):501-512

This paper is focused on the analysis of the performance of Stable Point Network (SPN) and Coherent Pixel Technique (CPT), which are Advanced Differential Interferometry Techniques (A-DInSAR) that estimate, among other results, mean deformation velocity maps of the ground surface and displacement time series from a SAR dataset. The test site is the metropolitan area of the city of Murcia (Spain) where a moderate slow subsidence induced by the overexploitation of aquifers is present. SAR data acquired between July 1995 and August 2005 from ERS and ENVISAT sensors have been processed by the SPN and CPT techniques and compared with in situ instrumental measurements assumed as reference. Experimental results have shown that both SPN and CPT techniques provide estimates of the deformation evolution in time with an absolute difference below 6 mm consistently in all comparisons: SPN vs extensometer, CPT vs extensometer and SPN vs CPT. The proposed validation and comparison experiment between both A-DInSAR techniques has been useful to observe their differences and complementarities.  相似文献   

Sedimentary processes in the Selvage sediment-wave field, NE Atlantic: new insights into the formation of sediment waves by turbidity currents   总被引：5，自引：0，他引：5  

Russell B. Wynn  Philip P. E. Weaver  Gemma Ercilla  Dorrik A. V. Stow  & Douglas G. Masson 《Sedimentology》2000,47(6):1181-1197

An integrated geophysical and sedimentological investigation of the Selvage sediment-wave field has revealed that the sediment waves are formed beneath unconfined turbidity currents. The sediment waves occur on the lower continental rise and display wavelengths of up to 1 km and wave heights of up to 6 m. Wave sediments consist of interbedded turbidites and pelagic/hemipelagic marls and oozes. Nannofossil-based dating of the sediments indicates a bulk sedimentation rate of 2·4 cm 1000 years^–1, and the waves are migrating upslope at a rate of 0·28 m 1000 years^–1. Sediment provenance studies reveal that the turbidity currents maintaining the waves are largely sourced from volcanic islands to the south. Investigation of existing models for sediment-wave formation leads to the conclusion that the Selvage sediment waves form as giant antidunes. Simple numerical modelling reveals that turbidity currents crossing the wave field have internal Froude numbers of 0·5–1·9, which is very close to the antidune existence limits. Depositional flow velocities range from <6 to 125 cm^–1. There is a rapid increase in wavelength and flow thickness in the upper 10 km of the wave field, which is unexpected, as the slope angle remains relatively constant. This anomaly is possibly linked to a topographic obstacle just upslope of the sediment waves. Flows passing over the obstacle may undergo a hydraulic jump at its boundary, leading to an increase in flow thickness. In the lower 15 km of the wave field, flow thickness decreases downslope by 60%, which is comparable with results obtained for other unconfined turbidity currents undergoing flow expansion.  相似文献   

Arabia Terra,Mars: Tectonic and Palaeoclimatic Evolution of a Remarkable Sector of Martian Lithosphere     

Anguita  Francisco  Anguita  Jorge  Castilla  Gabriel  De La Casa  Miguel-Angel  Domínguez  José-María  Herrera  Raquel  Llanes  Pilar  López  Mónica  Martínez  Vicente 《Earth, Moon, and Planets》1997,77(1):55-72

A regional geologic study of Arabia Terra, a densely cratered area of Mars northern hemisphere, has revealed the individuality of this province. This is best expressed by an equatorial belt with a crater age distinctly younger as compared to the northern part of Arabia Terra and to Noachis Terra to the south. We interpret this as an incipient back-arc system provoked by the subduction of Mars lowlands under Arabia Terra during Noachian times. The regional fracture patterns are also best explained in this manner, making it unnecessary to appeal to a rotational instability of the planet, which is not supported by the palaeoclimatic indicators in the area. This model could be the first regional-scale confirmation of Sleep's (1994) hypothesis of a limited plate consumption as an explanation of the martian dichotomy. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Non-topological solitons as the possible origin of intrinsic extragalactic redshifts     

L. Herrera 《Astrophysics and Space Science》1994,215(1):131-133

The eleven-year sunspot cycles are considered to represent one of the solar activities. The daily observations of the sunspots in the KAAU Solar Observatory (KAAUSO) have been utilised to reduce a period of the present solar cycle, using Fourier technique. The highest peak in the amplitude spectrum was for a frequency of 0.00029 day^–1, for which the maximum occurred mid 1990.  相似文献   

Boundary methods in water resources     

I. Herrera 《Advances in water resources》1982,5(3):130-135

A brief review of boundary methods is presented. Emphasis is placed on alternatives to boundary integral equations. Different theoretical questions required to give a firm foundation to these procedures are discussed. Extensions to non-linear problems are explained. Examples of application to fluid problems are included.  相似文献   

Supernovae: Where and why do they break off?     

L. Herrera  L. A. Núñez 《Astrophysics and Space Science》1992,188(1):9-18

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Instrumental monitoring of the subsidence due to groundwater withdrawal in the city of Murcia (Spain)     

Juan Manuel Pardo  Antonio Lozano  Gerardo Herrera  Joaquín Mulas  Ángel Rodríguez 《Environmental Earth Sciences》2013,70(5):1957-1963

This paper presents the results of investigations of the generalized subsidence occurring in and around the city of Murcia, Spain. Based on this research, this is the first integrated investigation of its type performed in Spain. The phenomenon of ground consolidation in the city of Murcia leads to the appearance of severe cracking and settlement in buildings. Subsidence is the result of two factors: on the one hand, the nature of the ground in this area, as it is made of recent deposits of clay and soft limes filled in with clay–lime backfills in the top layers. On the other hand, the increase in groundwater withdrawal during the 1992–95 drought led to a decrease in the water level of a magnitude never before recorded in the city. The risk prevention management suggested convenience of the installation of a measurement network to study and follow the phenomena of the subsidence to quantify it and to calibrate this theoretical model. This network is composed of extensometers and piezometers, the best devices to measure moderate ground movements, which is the case of Murcia. The first phase (Phase I) of this study of ground settlement in the metropolitan area of Murcia involved the installation of a network with 22 extensometers and taking the first measurement series. In a second phase (Phase II), during a period of 4 years, measurements with extensometers were performed to make the analysis and calibration of the theoretical model. Experience and data analysis showed the convenience of installation of new control points with an incremental extensometer and a piezometer in close position with the aim of precisely correlating piezometric levels with the observed subsidence. The third phase (Phase III) started in 2007, a new control technique, based on radar interferometry (InSAR), is being employed to provide information about subsidence in areas not previously monitored.  相似文献   

Parallel Algorithms for Computational Models of Geophysical Systems     

Antonio Carrillo-Ledesma  Ismael Herrera  Luis M. de la Cruz 《Geofísica Internacional》2013,52(3):293-309

Mathematical models of many geophysical systems are based on the computational processing of large-scale algebraic systems. The most advanced computational tools are based on massively parallel processors. The most effective software for solving partial differential equations in parallel intends to achieve the DDM-paradigm. A set of four algorithms, the DVS-algorithms, which achieve it, and of very general applicability, has recently been developed and here they are explained. Also, their application to problems that frequently occur in Geophysics is illustrated.  相似文献   

Geostatistical simulation of spatial variability of convective storms in Mexico City Valley     

Javier Méndez-Venegas  Graciela S. Herrera  Martín A. Díaz-Viera  Arturo Valdés-Manzanilla 《Geofísica Internacional》2013,52(2):111-120

Precipitation is one of the main components of the hydrological cycle and knowledge of its spatial distribution is fundamental for the prediction of other closely related environmental variables, for example, runoff, flooding and aquifer recharge. Most of the precipitation in Mexico City is due to convective storms characterized by a high spatial variability, implying that modeling its behavior is very complex. In this work stochastic simulation techniques with a geostatistical approach were applied to model the spatial variability of the rainfall of three convective storms. The analysis of the results shows that using the proposed methodology spatial distributions of rain are obtained that reproduce the statistical characteristics present in the available information.  相似文献   

Estimation and evaluation of hourly updated global GPS Zenith Total Delays over ten months   总被引：1，自引：0，他引：1  

Jan Dousa  Gemma V. Bennitt 《GPS Solutions》2013,17(4):453-464

The EUMETNET EIG GNSS Water Vapour Programme (E-GVAP) is responsible for the coordination of near real time GPS Zenith Total Delay (ZTD) production in Europe and for aiding the development of ZTD assimilation into Numerical Weather Prediction (NWP) models. Since 2000, the Geodetic Observatory Pecný (GOP) has been routinely estimating regional ZTDs in near real time. In 2010, GOP developed a modified processing system in order to provide the first optimal and robust ZTD solution with a global scope and hourly upgrade, fulfilling the requirements for assimilation into operational NWP models. Since July 2010, the GOP global tropospheric product has consisted of about 90 sites and has contributed routinely in a testing mode into the E-GVAP database. Global near real time ZTDs generated over ten months have been evaluated with respect to IGS and EUREF routine post-processed ZTD products, ZTDs integrated from radiosonde profiles, and ZTDs calculated from the Met Office global NWP model. Comparison with the GNSS post-processed solutions gives standard deviations of 3–6 mm in ZTD and biases of 1–2 mm, which is comparable to GOP regional near real time solution, however, for some isolated or low data quality stations up to 20 % quality decrease can be found. Comparison with NWP shows a latitudinal trend in the standard deviation with values as low as 4 mm at high latitudes, increasing to almost 20 mm in the tropics, and a lack of variability in the model background ZTD in the tropics. The evaluation with global radiosondes gives ZTD standard deviation of 5–16 mm, which is comparable with previous studies in European scope. Since the 10-month comparison gave satisfactory results, GOP was asked by UK Met Office to disseminate the global product to the end users via the Global Telecommunications System. Since 10 October 2011, the GOP global ZTD product configuration has been extended to about 164 global stations and still processed within 10 min. However, in GOP routine contribution to E-GVAP, about 124 stations are available in general due to hourly data latency above 30 min or data gaps.  相似文献