APPLICATION OF TERRASAR-X DATA TO THE MONITORING OF URBAN SUBSIDENCE IN THE CITY OF MURCIA Daniel Monells (1) , Giuseppe Centolanza (1) , Jordi J. Mallorqui (1) , Sergi Duque (1) , Paco López-Dekker (1,4) , Roberto Tomás (2) , Gerardo Herrera (3) , Juan M. López-Sánchez (2) , Fernando Vicente (2) , Victor D. Navarro-Sanchez (2) , Joaquín Mulas (3) (1) Remote Sensing Lab.-UPC, Spain; (2) Universidad de Alicante (UA), Spain; (3) Instituto Geológico y Minero (IGME), Spain; (4) DLR, Germany ABSTRACT 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. Index Terms— Differential, Interferometry, Subsidence, Monitoring 1. INTRODUCTION Orbital DInSAR is a technique widely used to survey the surface of the Earth and monitor hazards due to natural and human agents, such as earthquakes or mining [1][2][3]. Nowadays, there are a large number of satellites in orbit carrying SAR instruments able to perform this monitoring. In this work we will make a comparison of the results of urban subsidence moni-toring obtained using data from veteran satellites ERS-2 and ENVISAT and the new satellite TerraSAR-X. The objective of the paper is to compare the performance of each system under different aspects, such as the management and detection of different kinds of targets (distributed or deterministic), the preservation of the coherence/phase stability and its temporal evolution, and a comparison of the de-formation results using each set of data. This work has been supported by the Spanish MICINN and European Union FEDER funds under project TEC2008-06764-C02. The TerraSAR-X images were provided by DLR in the framework of the scientific project GEO0389. ERS and ENVISAT data were provided by ESA in the framework of the CAT1 1 project 2494. The Cartographical Service of Murcia (CARTOMUR) has provided the DEM and orto-images used in this work. 2. THE COHERENT PIXELS TECHNIQUE (CPT) The Coherent Pixels Technique has been widely used for monitoring urban subsidence [3]. The algorithm can use both coherence and amplitude stability criteria to perform pixels selection. The former is more suited for detecting stable distributed targets and the latter for detecting the so- called Permanent Scatterers (PS). The retrieval of the deformation time-series is done in two steps. Firstly, a linear model adjustment to data provides the linear velocity of deformation, the DEM error and the azimuth position of the PS (only for amplitude-based processing when large Dopplers are present). Secondly, the non-linear processing retrieves the non-linear deformation and the atmospheric phase screen for each image. 3. THE CITY OF MURCIA TEST-SITE Subsidence has occurred in the metropolitan area of Murcia City (SE Spain) as a result of soil consolidation due to piezometric level depletion caused by excessive pumping of groundwater. The study area is part of Segura River valley located in the oriental sector of the Betic Cordillera. Permian and Triassic deformed materials corresponding to the Internal Zones of the Betic Cordillera make up the basement. The basin filling comprises Upper Miocene to Quaternary sediment fluvial deposits. Younger sediments are highly compressible and the most problematic from a geotechnical point of view [4]. They constitute an aquifer system that is divided in two units. The superficial aquifer reaches 30 meters below the surface, and it is formed by recent clay, silt and sands facies. The deep aquifer, located below, is composed of a sequence of gravels and sands alternating with confined silt and clay layers. Subsidence is triggered by the excessive water pumping of the first layer of deep aquifer. In fact a piezometric level decline between 5 and 15 m was measured on this layer during recent drought periods: 1980–1983, 1993–1995 and 2005–2008. After the second drought period, ground subsidence was triggered causing damages in buildings and other structures with an estimated cost of 50 million Euros, generating a 3506 978-1-4244-9566-5/10/$26.00 ©2010 IEEE IGARSS 2010