M. Foumelis

Seismotectonic investigation on the Bam earthquake prone area (Iran) based on ASAR interferometry

In this study the Satellite Radar Interferometry (InSAR) was applied to investigate the crustal deformation caused by the Bam Earthquake (M/sub w/=6.5) that occurred in Iran on December 26, 2003. It was a multiple seismic event that destroyed the historical City of Bam and provoked great damages in the urban centers of the region. The Bam area in the south-eastern part of Iran is an active seismic zone and the Bam Fault System is comprised by three specific segments (north, east and SE of Bam). The three-pass interferometric technique was applied using ENVISAT ASAR scenes. According to the interferometric processing results subsidence has occurred in the area NE of Bam City, while dextral strike-slip displacement has taken place in the southern area of Bam. The last deformation could be attribute to a parallel hidden segment of the Bam Fault that is reaching the surface according to the shear displacement during the earthquake.

Ground deformation monitoring of the Santorini volcano using satellite radar interferometry

The island complex of Santorini is located at the central part of the Hellenic Volcanic Arc in the Southern Aegean Sea. This volcano complex basically consists of five islands, Thera, Therassia, Palea Kammeni, Nea Kammeni and Aspronisi forming a caldera of 83 km/sup 2/ with 390 m depth. The last significant volcanic activity took place between 1925 and 1950. However, the volcano is at a rest state during the last 50 years. The present work refers to the ground deformation monitoring of the area using ERS1, ERS2 and Envisat radar scenes from 1993 to 2004. A total number of four ERS1&2 SLC radar images covering the period 1993 to 1999, and two ENVISAT ASAR images for the period 2003-2004 were used. The method applied was the two-passes interferometry with a contribution of a high resolution Digital Elevation Model. The interferometric results show that although the volcano is at a rest phase, in the two volcanic centers of Pales and Nea Kammeni ground deformation (subsidence) of 62 mm along the line of sight of the satellite was detected.

Investigation on Bam (Iran) earthquake 26/12/03 based on interferometric coherence

The Bam earthquake of 26/12/2003 (Mw=6.5) demolished the city of Bam and provoked serious damages in Baravat city, which are located in a tectonic intersection zone in the SE of Iran. The present study focus on Bam earthquake seismotectonic investigations and damages assessment based on Envisat interferometric coherence images. Field observations, SAR magnitude and multitemporal SAR images were also used to support and verify the coherence image interpretation. Concerning the damages assessment the results were very poor in terms of recognition and operational capabilities. On the contrary the used of interferometric coherence image came to be very useful for seismic fault and rupture zones detection. Through this method a hidden fault, a parallel segment of the already known Bam fault, was identified.

Remotely sensing data and thematic mapping for sustainable developing in Sperchios river basin (Central Greece)

Policy and decision making in the context of sustainable development requires rapid, effective and efficient access to and integration of appropriate current information from a wide range of sources, including land cover changes information derived from remotely sensed data. Geomorphic factors, such as altitude, slope, aspect and lithology presented in the area comprise the main parameters, including the climate, influencing the distribution of land cover. The use of a Geographic Information System (GIS) allows further spatial analysis of the data derived from remotely sensed images and digital terrain spatial models, and analysis of the impact of land cover change on regional sustainable development. The remotely sensing data used in this study was Landsat 5 TM and Landsat 7 ETM+ images. Normalized Difference Vegetation Index (NDVI) and Selective Principal Component Analysis (SPCA) techniques were applied to detect land cover change and especially vegetation changes from multitemporal satellite data. The area under study is the basin of River Sperchios, which covers an area of some 1.780 km2, is approximately 60-80 km long, 20-30 km wide with its southern and western flanks characterized by high elevations and steep slopes, whilst its northern flank presents lower elevations and more gently slopes. The conclusions obtained show that extensive land cover changes has occurred in the last decades as a result of both natural forces and human activities, which has in turn impacted on the regional sustainable development. The results thus provide very useful information to local government for decision making and policy planning.

Detection of ground deformation in the broader area of Sharm El-Shiekh (Sinai Peninsula, Egypt) by SAR interferometry

Sharm El-Shiekh area is located in the most southern part of Sinai Peninsula boarded by the Gulf of Suez to the west and by the Gulf of Aqaba to the east. The present study concerns the application of Multibaseline/Stacking Differential SAR Interferometry (DInSAR) in order to monitor ground deformation rates in the southern part of Sharm El-Shiekh area. The specific technique was applied in order to reduce the influence of atmospheric effects on ground deformation estimates. For this purpose a total number of 24 ENVISAT ASAR scenes covering the period between 2002 and 2008 were processed and analysed. Interferometric results show both patterns of uplift and downlift in the study area. Specifically an area along the coastline with a N-S direction, corresponding to the build up zone of Sharm El-Shiekh, shows average annual subsidence rates between -5 and -7 mm/yr along the line of sight (LOS). On the contrary, Sharm El Maya, an inner zone parallel to the above subsided area, shows slant range uplift of around 5 mm/yr. The obtained results of SAR inteferometry probably indicate the presence of an active fault that affects the coastal zones of Sharm El-Shiekh area.

Average coherence image derived observations over an urban area: the case of Athens city

In the present study coherence observations, in relation to the land-cover type, obtained using 20 C-band ERS SAR Single Look Complex (SLC) VV-polarization images acquired in descending mode over the metropolitan area of Athens covering the period 1992-1999 are presented. A straightforward approach using a single master SAR image on which the other images are mapped was adopted ensuring perfect registration of the interferometric results. After generating single coherence images, with temporal separation varying between 138 and 1335 days, an averaging procedure followed leading to the average coherence image. In order to identify and statistically interpret the properties of selected land cover types in terms of average degree of coherence, very high resolution QuickBird imagery was downloaded from Google Earth environment. The final geocoding of the average coherence image has been improved using common features in the coherence image and the very high-resolution QuickBird image. Overlay of coherence product on the QuickBird image allows correlating the level of coherence with characteristics and properties of the urban shell. As urban areas are considered of high coherence, observations of this type permit to investigate and evaluate their phase stability in details.