Factors determining subsidence in urbanized floodplains: evidence from MT‐InSAR in Seville (southern Spain)

Major rivers have traditionally been linked with important human settlements throughout history. The growth of cities over recent river deposits makes necessary the use of multidisciplinary approaches to characterize the evolution of drainage networks in urbanized areas. Since under‐consolidated fluvial sediments are especially sensitive to compaction, their spatial distribution, thickness, and mechanical behavior must be studied. Here, we report on subsidence in the city of Seville (Southern Spain) between 2003 and 2010, through the analysis of the results obtained with the Multi‐Temporal InSAR (MT‐InSAR) technique. In addition, the temporal evolution of the subsidence is correlated with the rainfall, the river water column and the piezometric level. Finally, we characterize the geotechnical parameters of the fluvial sediments and calculate the theoretical settlement in the most representative sectors. Deformation maps clearly indicate that the spatial extent of subsidence is controlled by the distribution of under‐consolidated fine‐grained fluvial sediments at heights comprised in the range of river level variation. This is clearly evident at the western margin of the river and the surroundings of its tributaries, and differs from rainfall results as consequence of the anthropic regulation of the river. On the other hand, this influence is not detected at the eastern margin due to the shallow presence of coarse‐grain consolidated sediments of different terrace levels. The derived results prove valuable for implementing urban planning strategies, and the InSAR technique can therefore be considered as a complementary tool to help unravel the subsidence tendency of cities located over under‐consolidated fluvial deposits. Copyright © 2017 John Wiley & Sons, Ltd.Departamento de Geodinámica, Universidad de Granada, EspañaDepartamento de Ingeniería Cartográfica, Geodésica y Fotogrametría, Universidad de Jaén, EspañaCentro de Estudios Avanzados en Ciencias de la Tierra (CEACTierra), Universidad de Jaén, EspañaInstituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Científicas, EspañaInstituto Andaluz de Ciencias de la Tierra, Universidad de Granada, EspañaDepartamento de Ingeniería Civil, Universidad de Granada, EspañaInstitute for Systems and Computer Engineering, Technology and Science, Universidade de Trás‐os‐Montes e Alto Douro, PortugalInstituto Geológico y Minero de España, EspañaDepartment of Radar Technology, Netherlands Organisation for Applied Scientific Research, Países BajosGrupo de Investigación Microgeodesia Jaén, Universidad de Jaén, EspañaDepartment of Geoscience and Remote Sensing, Delft University of Technology, Países Bajo

PS-InSAR processing methodologies in the detection of field surface deformation—Study of the Granada basin (Central Betic Cordilleras, southern Spain)

9 páginas, 8 figuras, 1 tabla.Differential SAR interferometry (DInSAR) is a very effective technique for measuring crustal deformation. However, almost all interferograms include large areas where the signals decorrelate and no measurements are possible. Persistent scatterer interferometry (PS-InSAR) overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms. Two time series of 29 ERS-1/2 and 22 ENVISAT ASAR acquisitions of the Granada basin, located in the central sector of the Betic Cordillera (southern Spain), covering the period from 1992 to 2005, were analyzed. Rough topography of the study area associated to its moderate activity geodynamic setting, including faults and folds in an uplifting relief by the oblique Eurasian–African plate convergence, poses a challenge for the application of interferometric techniques. The expected tectonic deformation rates are in the order of 1 mm/yr, which are at the feasibility limit of current InSAR techniques. In order to evaluate whether, under these conditions, InSAR techniques can still be used to monitor deformations we have applied and compared two PS-InSAR approaches: DePSI, the PS-InSAR package developed at Delft University of Technology (TU Delft) and StaMPS (Stanford Method for Persistent Scatterers) developed at Stanford University. Ground motion processes have been identified for the first time in the study area, the most significant process being a subsidence bowl located at the village of Otura. The idea behind this comparative study is to analyze which of the two PS-InSAR approaches considered might be more appropriate for the study of specific areas/environments and to attempt to evaluate the potentialities and benefits that could be derived for the integration of those methodologies.This research was supported by the European Space Agency (ESA) in the scope of 3858 and 3963 CAT-1 projects, the PR2006-0330, ESP2006-28463-E, CSD2006- 00041, and CGL 2006-06001 projects from Ministerio de Educación y Ciencia (Spain), the RNM-149 and RNM-282 research groups of the Junta de Andalucía (Spain) and Fundação para a Ciência e a Tecnologia (Portugal). TUDelft radar group and Stanford University are gratefully acknowledged for all the technical support. The SRTM data were provided by USGS/NASA.Peer reviewe

L-band and C-band InSAR studies of African volcanic areas

Radar interferometry has proven to be a very suitable, low-cost and accurate tool to measure surface displacements. We investigate several data fusion or time-series analysis strategies which aim to mitigate C-band InSAR restrictions for volcano deformation monitoring applications. The focus is on active African volcanic areas. Firstly, data fusion of C-band ENVISAT/ASAR and L-band ALOS/PALSAR sensors helps the determination of a rifting event sequence that took place in summer 2007 in Lake Natron area. The second strategy investigated is a new Wavelet Based InSAR time series applied on ERS-2 data covering the Nyiragongo-Nyamulagira area. It allows new ground displacements identifications outside the local rift valley. Lastly, PALSAR Quad-Pol POLInSAR applicability is explored for La Palma Island.Peer reviewe

L-band and C-band InSAR studies of African volcanic areas

Radar interferometry has proven to be a very suitable, low-cost and accurate tool to measure surface displacements. We investigate several data fusion or time-series analysis strategies which aim to mitigate C-band InSAR restrictions for volcano deformation monitoring applications. The focus is on active African volcanic areas. Firstly, data fusion of C-band ENVISAT/ASAR and L-band ALOS/PALSAR sensors helps the determination of a rifting event sequence that took place in summer 2007 in Lake Natron area. The second strategy investigated is a new Wavelet Based InSAR time series applied on ERS-2 data covering the Nyiragongo-Nyamulagira area. It allows new ground displacements identifications outside the local rift valley. Lastly, PALSAR Quad-Pol POLInSAR applicability is explored for La Palma Island.Peer reviewe