J. Mulas

Radar interferometry techniques for the study of ground subsidence phenomena: a review of practical issues through cases in Spain

Subsidence related to multiple natural and human-induced processes affects an increasing number of areas worldwide. Although this phenomenon may involve surface deformation with 3D displacement components, negative vertical movement, either progressive or episodic, tends to dominate. Over the last decades, differential SAR interferometry (DInSAR) has become a very useful remote sensing tool for accurately measuring the spatial and temporal evolution of surface displacements over broad areas. This work discusses the main advantages and limitations of addressing active subsidence phenomena by means of DInSAR techniques from an end-user point of view. Special attention is paid to the spatial and temporal resolution, the precision of the measurements, and the usefulness of the data. The presented analysis is focused on DInSAR results exploitation of various ground subsidence phenomena (groundwater withdrawal, soil compaction, mining subsidence, evaporite dissolution subsidence, and volcanic deformation) with different displacement patterns in a selection of subsidence areas in Spain. Finally, a cost comparative study is performed for the different techniques applied.

Control of deformation of buildings affected by subsidence using persistent scatterer interferometry

In this article, satellite radar data are analysed to control the deformation of the buildings of Murcia City (SE Spain) affected by subsidence. This phenomenon has occurred as a result of groundwater overexploitation in drought periods, and special attention is paid to the most recent drought which occurred between 2005 and 2008. In the first part of this work, the study area is presented followed by a description of the characteristics and effects of subsidence on the buildings of the urban area. Persistent scatterer interferometry is used to process a satellite base radar dataset measuring the temporal and the spatial evolution of subsidence. These results are analysed with respect to several factors that control subsidence mechanisms: water table decrease, thickness of the compressible layer and the type of foundation of the buildings. To validate these results, a detailed structural damage analysis of several buildings is presented. According to the results presented in this work, it may be concluded that damage of buildings is triggered by soil consolidation due to groundwater overexploitation, demonstrating that the inclusion of this technique can be particularly interesting in structural monitoring framework of civil infrastructures, as a complementary tool to control subsidence damage.

Application of TerraSAR-X data to the monitoring of urban subsidence in the city of Murcia

This paper presents an analysis of the performance of TerraSAR-X for subsidence monitoring in urban areas. The city of Murcia has been selected as a test-site due to its high deformation rate and the set of extensometers deployed along the city that provide validation data. The obtained results have been compared with those ob-tained from ERS/ENVISAT data belonging to the same period and validated with the in-situ measurements.

Losses Caused by Recent Mass-Movements in Majorca (Spain)

The main income of the island of Majorca (Balearic Islands, Spain) comes from tourism (83 % of its GDP), as it welcomes over nine million visitors each year. During the years 2008–2010, Majorca experienced one of the coldest and wettest winters in living memory. The result was that 34 mass movements were triggered, distributed along the Tramuntana Range, in the northwest sector of the island, namely 14 rockfalls, one rock avalanche, 15 landslides and 4 karstic collapses. Fortunately, there were no deaths but there were numerous cases of damage to dwellings, holiday apartment blocks, barns and power stations, and especially the road network in the range, most significantly the numerous blockages on the Ma-10 road, which caused significant economic losses in the different tourist resorts. On the southern coast of the range, 17 holiday homes have been evacuated recently due to the impending risk of a large rockfall. Total economic losses are valued at approximately 11M Euro, which represents 0.042 % of the Balearic Autonomous Region GDP.

Recent Mass Movements in the Tramuntana Range (Majorca, Spain)

Between 2008 and 2010, the island of Majorca (Spain) experienced the coldest and wettest winters of the last 40 years. Accumulated rainfall was twice the average and values of intense rainfall up to 296mm/24h were recorded. Additionally, high precipitation coincided with anomalous, low temperatures and freezing in the highest zones of the Tramuntana range (NW sector of the island). As a result, 34 mass movements were recorded: 14 rockfalls, 1 rock avalanche, 15 landslides and 4 karstic collapses. The geological structure determines the distribution and the failure pattern of the movements. Most of the movements have taken place after antecedent rainfall over 800mm. Intense rainfall >90mm/24h also caused rockfalls. Additionally, the rockfalls have also occurred after several freeze-thaw cycles, being a determining and unusual factor in this warm region. The results aim to contribute to the design of an early warning system coordinating emergency, infrastructure and meteorological centres, in a region of high risk.