Three-Dimensional Nepal Earthquake Displacement Using Hybrid Genetic Algorithm Phase Unwrapping from Sentinel-1A Satellite

Introduction: Geophysicists had forewarned for decades that Nepal was exposed to a deadly earthquake, exceptionally despite its geology, urbanization and architecture. Gorkha earthquake is the most horrible natural disaster to crash into Nepal since the 1934 Nepal-Bihar earthquake. Gorkha earthquake occurred on April 25, 2015, at 11:56 NST and killed more than 10,000 people and injured more than 23,000 population. Objective: The main objective of this work is to utilize hybrid genetic algorithm for three-dimensional phase unwrapping of Nepal earthquake displacement using Sentinel-1A satellite. The three-dimensional best-path avoiding singularity loops (3DBPASL) algorithm was implemented to perform 3D Sentinel-1A satellite phase unwrapping. The hybrid genetic algorithm (HGA) was used to achieve 3DBPASL phase matching. Advancely, the errors in phase decorrelation were reduced by optimization of 3DBPASL using HGA. Results: The findings indicate a few cm of ground deformation and vertical northern of Kathmandu. Approximately, an area of 12,000 km2 has been drifted also the northern of Kathmandu. Further, each fringe of colour represents about 2.5 cm of deformation. The large amount of fringes indicates a large deformation pattern with ground motions of 3 m. Conclusion: In conclusion, HGA can be used to produce accurate 3D quake deformation using Sentinel-1A satellite

Mexico City Subsidence Measured by InSAR Time Series: Joint Analysis Using PS and SBAS Approaches

International audienceIn multi-temporal InSAR processing, both the Permanent Scatterer (PS) and Small BAseline Subset (SBAS) approaches are optimized to obtain ground displacement rates with a nominal accuracy of millimeters per year. In this paper, we investigate how applying both approaches to Mexico City subsidence validates the InSAR time series results and brings complementary information to the subsidence pattern. We apply the PS approach (Gamma-IPTA chain) and an ad-hoc SBAS approach on 38 ENVISAT images from November 2002 to March 2007 to map the Mexico City subsidence. The subsidence rate maps obtained by both approaches are compared quantitatively and analyzed at different steps of the PS processing. The inter-comparison is done separately for low-pass (LP) and high-pass (HP) filtered difference maps to take the complementarity of both approaches at different scales into account. The inter-comparison shows that the differential subsidence map obtained by the SBAS approach describes the local features associated with urban constructions and infrastructures, while the PS approach quantitatively characterizes the motion of individual targets. The latter information, once related to the type of building foundations, should be essential to quantify the relative importance of surface loads, surface drying and drying due to aquifer over-exploitation, in subsoil compaction

Non-local methods for InSAR parameters estimation

In the thesis work the nonlocal paradigm has been investigated in the framework of Multitemporal SAR Interferometry, e.g. Differential Interferometry, Tomography, etc., and single InSAR pair, e.g. DEM generation. In the former, Adaptive Multi-Looking methods have been developed for the generation of interferometric data-stacks. Following the nonlocal approach, the proposed methods rely only on similar pixels according to a suitable similarity measure that exploits the stack's temporal information. An hybrid approach that jointly uses the nonlocal paradigm and transform domain filtering has been investigated for InSAR pair phase estimation. On the track of the BM3D and SARBM3D algorithms, different approaches to the filtering in the transform domain are investigated. Furthermore, a novel approach to the similarity computation and filtering, based on a relative-topography content of the interferometric phase rather than its absolute value, is proposed

Integrated analysis of building vulnerability in urban areas affected by slow-moving, intermittent landslides using SAR Interferometry

Slow-moving landslides are a natural hazard which affects wide areas in the world causing relevant economic damage to structures and infrastructures. To this reason, the analysis of landslide-induced consequences plays a key role in risk prevention and mitigation activities. The thesis shows a general methodology which can be used to forecast spatial and temporal evolution of building vulnerability in urban settlements affected by slow-moving and intermittent landslides. Multi-level and integrated analysis of landslide kinematics and exposed elements allows to assess at different scales of representation and at different levels of accuracy, future conditions of damage of existing facilities. Satellite Radar Interferometry and in particular the Differential SAR Interferometry (DInSAR) technique has been successfully applied as a remote-sensing tool to provide information both on spatial and temporal landslide evolution and on interaction with structures in urban areas. Integration of C and X-band SAR data (acquired between 2002 and 2016) with conventional monitoring techniques allows to reach a thorough knowledge of landslide kinematics; subsequently, structural analyses to detect the relationship between slope movements and building damage have been performed, by using qualitative, semi-quantitative and quantitative approaches. Such methodology has been tested in Moio della Civitella urban settlement, Salerno Province, whose territory is affected by several slow-moving landslides. At small scale of representation, preliminary cause-effect relationship and the updating of landslide inventory map have been provided; at medium scale of analysis, vulnerability zoning map through matrix-approach and influence of vulnerability factors on performance of structures through fragility curves approach, have been defined. Finally, at a detailed scale, structural behavior of buildings has been investigated by means of analytical or numerical analyses. The proposed methodology could be applied to other scenarios affected by similar phenomena and once validated, can be valuably used for damage analysis and forecasting

Earth resources: A continuing bibliography with indexes (issue 51)

This bibliography lists 382 reports, articles and other documents introduced into the NASA scientific and technical information system between July 1 and September 30, 1986. Emphasis is placed on the use of remote sensing and geophysical instrumentation in spacecraft and aircraft to survey and inventory natural resources and urban areas. Subject matter is grouped according to agriculture and forestry, environmental changes and cultural resources, geodesy and cartography, geology and mineral resources, hydrology and water management, data processing and distribution systems, instrumentation and sensors, and economic analysis