Land subsidence phenomena in urbanized areas of

2 downloads 0 Views 7MB Size Report
In Greece, the Thessaly Plain [1-4], Kalochori village in the east sector of Thessaloniki ... of Florina Prefecture [12-14] are few examples of areas where land ...
Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

Land subsidence phenomena in urbanized areas of Attica observed by applying advanced DinSAR techniques Kaitantzian A. a, Parcharidis I. b, Loupasakis C. a a

Laboratory of Engineering Geology and Hydrogeology, School of Mining and Metallurgical Engineering, National Technical University of Athens, 9, Heroon Polytechniou Str., 157 80, Athens, Greece,+30-2107722069,+30-2107722087; b Department of Geography, Harokopio University of Athens, 70, El. Venizelou Str., 17671, Athens, Greece, +30-2109549345 ABSTRACT Synthetic Aperture Radar Interferometry (SAR) technology has been enabled to investigate the spatial distribution and temporal evolution of displacements occurring at the areas due to land subsidence related hazards. Land motion mapping data, produced by hybrid interferometric technique (Singular Value Decomposition algorithm) and PSI (Persistent Scatterer Interferometry) analysis, revealed vertical displacements affecting the Thriassio basin and the region of Moschato. The outcomes of these techniques provided important information about the spatial extent and time series of the surface deformation that should be evaluated considering the geological, hydrogeological, morphological and tectonic settings of the areas to assess land subsidence hazard mechanism. Keywords: Land subsidence, Singular Value Decomposition (SVD), Persistent Scatterer Interferometry (PSI), Thriassio basin, Moschato region

1. INTRODUCTION Land subsidence is a common phenomenon occurring in several areas worldwide and in many cases urbanized areas, causing damages in buildings and linear infrastructure with high economic cost. In Greece, the Thessaly Plain [1-4], Kalochori village in the east sector of Thessaloniki plain [5-11], the Amyntaio basin of Florina Prefecture [12-14] are few examples of areas where land subsidence phenomena has been identified and monitored. In recent years, Synthetic Aperture Radar Interferometry (SAR) technology has been enabled in order to enhance the ability of the researchers to resolve the spatial distribution and temporal evolution of displacements. This action highly important as the early detection of surface deformations allows taking measures before the outbreak of severe subsidence phenomena and therefore allows for timely protection of the affected areas. Specifically in the present study, PSI (Persistent Scatterer Interferometry) analysis and hybrid interferometric technique (Singular Value Decomposition algorithm) has been applied to detect ground deformations. The main difference between of these advanced DinSAR techniques is that PSI is a scatterer based interferometry whereas SVD is a pixel based interferometry. This paper is aimed to present and compare the results of PSI analysis and the first outcomes of the SVD technique for the urbanized areas of Attica. In addition, the evaluation of all available geological, geotechnical, hydrogeological and tectonic data is performed in order to identify the main causes of the observed ground deformations and to validate the contribution of the remote sensing data on the study of the phenomena.

2.CASE STUDIES 2.1. Thriassio basin The Thriassio basin is situated in the western part of the city of Athens covering an area of approximately 100km2 (Fig.1a). The geological units occurring in the study area are the Mesozoic and Paleozoic bedrock formations occupying the bordering mountains and the Quaternary deposits occupying the plain area, with increasing thickness towards the northwest part of the Aspropyrgos town (Fig.1b).

RS100 - 11 V. 1 (p.1 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes:

Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

According to the geotechnical boreholes drilled in the study, reaching down to depths varying from 20 to 35m, the Quaternary formations consist of fine grain materials (clays, silty clays, clays including organic material, sandy clays, silty sand) intercalated by coarse grain layers (clayey sand-gravels, gravels and cobbles). The Thriassio basin is bordered to the north by the normal Thriassio fault (Thr-Fault) with a NW-SE direction and a length of 15km, while in the east and in the west the Thriassio basin is bordered by faults with an NE–SW direction. The active normal Fili fault (Fl-Fault) is located 5km southeast of the study area and is expressed as an abrupt linear front extending about 6km in the general NW- SE direction and SW dip direction. The good alignment of ridges against this front indicates that this fault activated during the Sept. 7, 1999, 5, 9 R earthquake [15]. From a hydrogeological point of view two aquifers systems were distinguished at the plain of the Thriassio basin. The unconfined shallow aquifer extending in the upper Quaternary deposits and the karstic aquifer developing in the underling karstified carbonate formations that outcrop in the margins of the plain. A large number of well overexploit the groundwater leading to a sea-water intrusion front extending 8 to 10 Km away from the coast - line [16].

Fig.1.a)Location map and b) Geological map of the Thriassio basin.

2.2. Moschato region The study area is located in the southwestern part of the city of Athens with more than 25.000 inhabitants. It is situated between the rivers Kiffisos and Ilissos, at the W and E respectively, while the southern border of the study area is the Faliro bay (Fig.2a). The Moschato region is occupied by Quaternary sediments consisting of alluvial and dilluvial deposits. The Neogene basement is composed by marls, sandy marls, sandstones, conglomerates and limestones (Fig.2b). Thanks to the availability of geotechnical boreholes the Quaternary formations are classified in three horizons. The top horizon from the surface to a depth of 25m, consists of soft clay and fine sandy horizon in alternations. The second horizon, with a thickness up to 5m, consists of sandy silty clay layer. The deeper horizon consists of conglomerates and sandstones in alternations.

RS100 - 11 V. 1 (p.2 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes:

Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

With regard to the hydrogeological conditions, the above described stratigraphic pattern led to the development of an unconfined shallow aquifer and of a system of deeper confined aquifers.

Fig.2. a)Location map and b) Geological map of the Moschato region.

3.ADVANCED DInSAR TECHNIQUES 3.1 The PSI technique The PSI (Persistent Scatterer Interferometry) technique is based on the processing of several multi-temporal satellite SAR imagery (at least 15-20, or more) of the same target area. The current technique uses long stacks of radar dataset and analyzes the signals backscattered from the observed scene aiming to estimate and remove atmospheric artifacts[17]. The electromagnetic returns of electromagnetically stable, highly reflective point wise targets (the so-called Permanent Scatterers, (PS) is statistically processed and analyzed to retrieve estimates of the displacements occurred between different acquisitions [18-19]. PSs usually correspond to manmade structures (i.e. buildings, roads, bridge, monuments, pylons), as well as natural reflectors, such as outcropping rocks. Thanks to this multi-interferometric approach the LOS velocity can be estimated, at each Permanent Scatterer, with unprecedented accuracy, sometimes even better than 0.1 mm/year. Displacement time series can be retrieved, acquisition by acquisition, with accuracy on single measurements usually ranging from 1 to 3mm [20]. 3.2. The SVD hybrid interferometric technique The SVD (Singular Value Decomposition) technique creates single reference stack of deformation rates by using the first scene as master scene with zero deformation values. In this way any potential deformation values that may occur between two dates are added to the subsequent one, for each image acquisition until the last one. Therefore, creating a cumulative deformation history for each pixel that exists in the available time interval and thus enabling the creation of time series graphs. The benefit of this technique is that the non-linear deformation can be estimated without the need of a priori assumption of a deformation model or past knowledge and as any other multi-temporal approach, the mitigation of decorrelation phenomena and topographic inaccuracies are limited [21]. 3.3. SAR dataset and processing details Twenty Single Look Complex (SLC) images of ENVISAT ASAR have been processes with the advanced SVD technique. These images have been acquired along descending orbits between the period 2002–2010. The first step of SVD analysis is the selection of the most suitable multi-baseline network for the data sets based on the perpendicular and

RS100 - 11 V. 1 (p.3 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes:

Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

temporal baseline. 114 descending interferograms have been formed in total, by using a multi-reference interferogram generation method (Fig.3). Next, an adaptive phase filtering method has been applied to all interferograms, in order to improve the quality of the phase unwrapping step. Additionally, a baseline refinement has been performed in order to further improve the baseline estimation and consequently mitigate the errors. Then, starting from the multi-reference stack of unwrapped phases has been derived a single reference time series using Singular Value Decomposition (SVD) to obtain the least-squares solution for the phase time series.

Fig.3. Multi-baseline network for ASAR/ENVISAT

The new interferometric results were compared with a dataset of 56 SAR imagery in C band obtained from satellites ERS-1&2, acquired along descending orbits from 1992 to 2001. These available space born radar measurements data were processed with the Persistent Scatterer Interferometry (PSI) Wide Area Processing (WAP) technique by the German Space Agency (DLR) within the ESA Terrafirma project. Furthermore, the evaluation of the geological, geotechnical and hydrogeological conditions of the areas combined with the SVD and PSI data is performed in order to provide substantial information for the interpretation of the land subsidence phenomenon.

4. RESULTS AND DISCUSSION In the case of Thriassio basin, by correlating the two successive deformation patterns, presented at fig.4a and b, different trends can be identified. The SVD results of ENVISAT data from 2002 to 2010 indicate that the Elefsis town and the northern west part of the Thriassio basin have been exhibiting deformations of -3mm/yr along the Line of Sight (LOS). On the contrary, the PSI results of ERS 1&2 data, from 1992 to 2001, indicate that the entire area extending northwest of the Aspropyrgos town exhibits displacements ranging between -3 and -10 mm/yr, along the LOS.

RS100 - 11 V. 1 (p.4 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes:

Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

Fig.4. a) Velocities from 1992 to 2001 as derived by the PSI analysis of ERS1&2 data. b) Velocities from 2002 to 2010 as derived by the SVD analysis of ENVISAT data.

According to ground water level measurements referring to the time periods 1999 to 2001 and 2006 to 2008, the level of the piezometric surface in the Thriassio basin presented significant rise at the entire basin during the second period (Fig.5).This fact is clearly related with the change of the economical status at the industrial area of Thriassio basin during the last years of the economic crises. This change led to the reduction of the ground water consumption and to the gradual recharge of the aquifers. Furthermore, examining the isopiezometric curves map (Fig. 6) referring to the conditions of the shallow aquifer in October 1999, it can be easily identified that the depression cones caused by the private industrial drills are related with the areas affected by land subsidence (Fig 4a). So it is clear that the land subsidence phenomena occurring at the site are related with the overexploitation of the aquifers. So the reduction on the land subsidence deformations rates occurring during the period 2002 - 2010 is related with the rise of the ground water level. At this point it should be noted that the compaction of an aquifer system depends not only on the piezometric level variations, but also on the geotechnical characteristics of the aquifer deposits. According to the laboratory data the compression index (Cc) of the fine grained layers ranges from 0.084 to 0.495, indicating their high compressibility potential.

RS100 - 11 V. 1 (p.5 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes:

Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

Pi ezometric l evel (m)

Ground water level time series 12 10 8 6 4 2 0 -2 -4 -6

THR136 THR142 THR70 THR16 THR106 THR165

Time Fig.5. Ground water level time series (1999–2008) of the water wells indicated in fig.6.

Fig. 6. Isopiezometric curves map October 1999 (measurements data from author [22]).

In the case of Moschato region, land subsidence can be identified at the area extending between the riverbeds of Kiffisos and Ilissos River with LOS deformation rates of -1.5 to -6.9 mm/yr during the period 1992 - 2001 and of -1.5 to -3mm/yr for the period 2002-2010 (Fig.7).

RS100 - 11 V. 1 (p.6 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes:

Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

According to the available geotechnical data from authors [23] the alluvial deposits consist of soft clay of low to high plasticity (CL, CH) with loose to medium-dense, sandy silt-silty sand (SM) and silt (ML, CL-ML). By comparing the preconsolidation effective stresses with the effective geostatic stresses of the site it is clear that the materials are underconsolidated. This fact, combined with the high compression index of the clay layers justifies the manifestation of notable vertical displacements due to the natural compaction of the material.

Fig.7. a) Velocities from 1992 to 2001 as derived by the PSI analysis of ERS1&2 data b) Velocities from 2002 to 2010 as derived by the SVD analysis of ENVISAT data.

A comparison between the equal depth curves of the bedrock Athenian schist formations and the distribution of the vertical displacements indicates that the greater subsidence values have been observed in the area where the thickness of the deposits exceeds over the depth of 20m. In the mid-1990s the water level was measured to lie 6m below ground level [24]. Interestingly enough, according to resent measurements in 2016 the shallow aquifer appeared to be recovered. Concluding the occurring land subsidence phenomena at the Moschato region could be attributed primarily to the natural compaction of the fine grained alluvial deposits. Furthermore, the overexploitation of groundwater reservoir cannot be entirely excluded.

5. CONCLUSIONS The applied InSAR techniques of SVD and PSI contributed to the detection and estimation of the ground deformation in the Thriassio basin and the Moschato region between the period 1992-2010. The obtained interferometric results have been evaluated by the geological, hydrogeological and tectonic settings of the areas in order to provide substantial information for the interpretation of the land subsidence phenomenon. For the area of the Thriassio plain the most important factor causing displacements are the overexploitation of groundwater reservoir. The detected subsidence at the Moschato region is probably related to the natural compaction of the fine grained alluvial deposits. Overall, exploitation of remote sensing data is proved as a valuable and suitable technique for increasing knowledge about the extent and the rate of the deformations in areas that are affected by land subsidence.

RS100 - 11 V. 1 (p.7 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes:

Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

ACKNOWLEDGEMENTS The Terrafirma Extension project has funded the SAR imagery processing of the ERS1/2 data referring to the period 1992-2001. The Terrafirma project is one of the many services supported by the Global Monitoring for Environment and Security (GMES) Service Element Programme, promoted and financed by ESA. Also, the authors gratefully acknowledge the German Aerospace Centre (DLR) for having processed the ERS1/2 SAR data.

REFERENCES [1] Ilia I., Loupasakis C. and Tsangaratos P., "Assessing ground subsidence phenomena with persistent scatterer interferometry data in western Thessaly, Greece," Proc. of the 14th International Congress of the Geological Society of Greece L(3), 1693-1702 (2016). [2] Rozos, D., Sideri, D., Loupasakis, C., and Apostolidis, E., "Land subsidence due to excessive groundwater withdrawal, a case study from Stavros-Farsala site, west Thessaly Greece," Proc. of the 12th International Congress of the Geological Society of Greece 4, 1850-1857 (2010). [3] Kontogianni, V., Pytharouli, S., and Stiros, S., "Ground subsidence, Quaternary faults and vulnerability of utilities and transportation networks in Thessaly, Greece," Environ. Geol. 52, 1085-1095 (2007). [4] Kaplanides, A. and Fountoulis, D., "Subsidence phenomena and ground fissures in Larissa, Karla basin, Greece: their results in urban and rural environment," Eng. Geol. Environ., 729-735 (1997). [5] Costantini F., Mouratidis A., Schiavon G., and Sarti F., "Advanced InSAR techniques for deformation studies and for simulating the PS-assisted calibration procedure of Sentinel-1 data: Case study from Thessaloniki (Greece), based on the Envisat / ASAR archive," International Journal of Remote Sensing 37, 729-744 (2016). [6] Raspini, F., Loupasakis, C., Rozos, D., and Moretti, S., "Advanced interpretation of land subsidence by validating multi-interferometric SAR data: the case study of the Anthemountas basin (northern Greece)," Nat. Hazards Earth Syst. Sci. Discuss. 1, 1213-1256 (2013). [7] Loupasakis, C. and Rozos, D., "Land subsidence induced by water pumping in Kalochori village (north Greece) – simulation of the phenomenon by means of the finite element method," Q. J. Eng. Geol. Hydrog. 42, 369-382 (2009). [8] Raucoules, D., Parcharidis, I., Feurer, D., Novalli, F., Ferretti, A., Carnec, C., Lagios, E., Sakkas, V., Le Mouelic, S., Cooksley, G., and Hosford, S., "Ground deformation detection of the greater area of Thessaloniki (Northern Greece) using radar interferometry techniques," Nat. Hazards Earth Syst. Sci. 8, 779-788 (2008). [9] Psimoulis, P., Ghilardi, M., Fouache, E., and Stiros, S., "Subsidence and evolution of the Thessaloniki plain, Greece, based on historical levelling and GPS data," Eng. Geol. 90, 55-70 (2007). [10] Stiros, S. C., "Subsidence of the Thessaloniki (northern Greece) coastal plain, 1960–1999," Eng. Geol. 61, 243-256 (2001). [11] Andronopoulos, V., Rozos, D., and Hatzinakos I., "Subsidence phenomena in the industrial area of Thessaloniki, Greece," Land Subsidence 200, 59-69 (1991). [12] Tzampoglou P., Loupasakis C., "New data regarding the ground water level changes at the Amyntaio basin- Florina Prefecture, Greece, Athens, Greece," Proc. of the 14th International Congress of the Geological Society of Greece L(2), 1006-1015 (2016). [13] Loupasakis C., Agelitsa B., Rozos D., Spanou N., "Mining geohazards—land subsidence caused by the dewatering of opencast coal mines: The case study of the Amyntaio coal mine, Florina, Greece," Natural Hazards 70, 675-691 (2014). [14] Soulios, G., Tsapanos, T., Voudouris, K., Kaklis, T., Mattas, C., and Sotiriadis, M., "Ruptures on surface and buildings due to land subsidence in Anargyri village (Florina Prefecture, Macedonia)," Environ. Earth Sci. 5, 505-512 (2011). [15] Pavlides S. B., Papadopoulos G., Ganas A., "The Fault that Caused the Athens September 1999 Ms = 5.9 Earthquake: Field Observations," Natural Hazards 27(1), 61-84 (2002). [16] Kounis, G. , "Evaluation of Vulnerability and quality of groundwater Resources in Greece," Technical Report (in Greek), Institute of Geology and Mineral Exploration of Greece, Athens (1986). [17] Adam, N., Rodriguez Gonzalez, F., Parizzi, A., and Liebhart, W., "Wide area persistent scatterer Interferometry," Proc. of the International Geoscience and Remote Sensing 6, 1481-1484 (2011). [18] Ferretti, A., Prati, C., and Rocca F., "Nonlinear subsidence rate estimation using Permanent Scatterers in differential SAR interferometry," IEEE T. Geosci. Remote 38, 2202 - 2212 (2000).

RS100 - 11 V. 1 (p.8 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes:

Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact [email protected] with any questions or concerns.

[19] Ferretti, A., Fumagalli, A., Novali, F., Prati, C., Rocca, F., and Rucci, A., "A new algorithm for processing interferometric data-stacks," IEEE T. Geosci. Remote 99, 1-11 (2011). [20] Colesanti, C., Ferretti, A., Prati, C., and Rocca, F., "Monitoring landslides and tectonic motion with the Permanent Scatterers technique," Eng. Geol. 68, 3-14 (2003). [21] Goel, K., Adam, N. and Minet, C., "Long term analysis of strong non-linear deformations induced by coal mining using the SBAS technique," In ESA Fringe Symp , 19-23 (2011). [22] Parashoudis, V., "Hydrogeological study of Western Attica (Megara Basin and Thriassio Field)," Ministry of Agriculture, Direction of Geology- Hydrology, Department of hydrologic boreholes and mathematical models, Report in Greek (2002). [23] Koukis G. and Sabatakakis N., "Engineering geological environment of Athens, Greece," Bull. Eng. Geol. Environ 59, 127-135 (2000). [24] Koumantakis I., "Research of hydrogeological conditions and of the operating procedures of the ground water in the basin of Attica," Main Issue, (Α΄ and Β΄ Phase), research program in the years 1996 and 1997 performed by the research team of the Section of Geological Sciences in cooperation with the Organization of Planning and Environmental Protection οf Athens (1997).

RS100 - 11 V. 1 (p.9 of 9) / Color: No / Format: A4 / Date: 3/4/2017 11:08:01 PM SPIE USE: ____ DB Check, ____ Prod Check, Notes: