1. Long and short term monitoring of ground deformation in Thessaly basin using space-based SAR Interferometry
Harokopio University of Athens
Department of Geography
PhD Candidacy Oral Examination by
Falah Atta Fakhri
Supervisors: Dr. Issaak Parcharidis
Dr. George Mighiros
Dr. Efthimis Karymbalis
Tuesday, June 25, 2013

2. Agenda Chapter One: Introduction
Chapter Two: Data acquisition and SAR interferometric techniques and processing
Chapter Three: Impact of groundwater on ground deformation.
Chapter Four: Impact of fault movement and earthquakes on ground deformation
Chapter Five: Impact of lithology types on ground deformation
Chapter Six: Impact of soil on ground deformation
Chapter Seven: The conclusions derived from this research study and Discussion .

3. Chapter One: Introduction PREFACE
Natural hazards comprise:
Hydro-meteorological hazards, which include floods and flash floods, droughts, wildfires, tropical cyclones and hurricanes, and severe storms.
Geological hazards, which include tectonic movement, earthquakes, tsunamis, volcanoes and explosive crater lakes, landslides, mudflows, erosion, and siltation.
Human-induced hazards comprise:
which include wars, groundwater and oil withdrawal, mining, and land degradation.
Together, all of these hazards contribute to serious environmental problems which in consequence affect and destroy the economic development of countries and finally, in turn, impact on all walks of life.

4. Study area
The study area is located in the eastern part of the northern Thessaly Plain in central of Greece.

5. Thessaly plain, indicating that the study area exists within the frames of ascending and descending radar image tracks

6. Study area problems and constraints
The study area suffers from a ground deformation phenomenon which affects civil construction and agricultural activity.
Furthermore it is a very complicated area due to the distribution of human hazards, which include groundwater withdrawal, and due to the presence of natural hazards for instance active tectonics.

7. SAR Interferometry
This new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by spaceborne SAR at two distinct times.

8. SAR Interferometric Techniques
Repeated pass Interferometry (Conventional InSAR)
In repeat-pass InSAR, two or more SAR images are acquired at different times with the same or a corresponding sensor from almost identical aspect angles.
Interferometric Stacking
The basic idea of interferogram stacking is to combine multiple observations into a single result.
Persistent Scatterers Interferometry (PSI)
This technique exploits temporal and spatial characteristics of interferometric signatures, collected from point targets.

9. Objectives of the Research Study
1- To evaluate the possibility of applying SAR interferometric techniques to monitor and map ground deformation in urban and agricultural lands over the long and short terms.
2- To investigate and identify the causes of ground deformation.
3- To evaluate the possibility of recognizing each individual cause of ground deformation by monitoring the time series behavior of ground deformation using the statistical results of SAR interferometric techniques.

10. 4- To apply spatial and qualitative correlations between ground deformation and parameters (precipitation, groundwater, fault movement, earthquake, lithology, and soil) to reveal the reality of ground deformation within the study area.

11. Flowchart of study research methodology
Additional data collection
SAR interferometry
Geology
Soil
Hydrology and hydrogeology
Meteorology
Data acquisition
Field- work
Thematic maps
Preprocessing
Persistent scatterer interferometry
Repeated pass interferometry
Stacking interferometry
Data management
Development of geographic information system
Production and
interpretation of deformation maps
Create spatial correlation
Create statistical correlation
Results

12. Chapter Two: Data acquisition and SAR interferometric techniques and processing
Data and Methodology
SAR Data Selection and Interferometric Processing (Ascending Track 143)
The total dataset consists of 24 Single Look Complex (SLC) SAR C-band images of ERS-1/2, during 1995–2000. Additionally, 15 SLC images of ENVISAT ASAR acquired during 2003–2008 by ESA, which cover the study area, have also been selected along this track.

13. Flowchart of preprocessing ASR images
Processing raw data to obtain SLC format images
Geometrical correction
Add the parameters of orbits
Estimate perpendicular baselines of all the selected images
Multi-look
crop image;
Resample images by estimating initial range and azimuth offsets
Corregister of SLC images
Simulation SLC SAR images with the
DEM , 90 (m) (SRTM)
Flowchart of preprocessing ASR images

14. Multi-look average image ascending track highlighting the study area and the mountains around the basin and urban area

15. Results and discussion
Repeated pass interferometry processing
Master image Slave image B┴ (m) Interval Days

16. Coherence map for time interval 19960228_19960403 ascending track
LARISA

17. Differential interferogram for time interval 19960228–19960403 ascending track
LARISA

18. Interferometric stacking processing
Average coherence for time interval 1995–2008 ascending track highlighting the coherence of the reference point inside the red circle
LARISA

19. Ground deformation rates along LOS direction deduced by interferometric stacking, for the considered time intervals (1995–2008) Ascending track and different acquisition. Background is an average of multi-look SAR intensities. The selected reference point is marked with a green Bp is m, 29 interferograms
LARISA

20. Persistent (Permanent) Scatterers Interferometric (PSI)
Distribution of geo-coded radar targets (persistent scatterers) in Larissa basin before expansion. The average in line of sight (LOS) velocity for the period (1995–2006) number of points are 1866
LARISA

21. Distribution of geo-coded radar targets (persistent scatterers) in Larissa basin after expansion. The average in line of sight (LOS) velocity for the period (1995–2006) number of points are 62551
LARISA

22. SAR Data Selection and Interferometric Processing (Descending Track 279)
The total dataset consists of 48 SLC SAR C-band images of ERS-1/2 from 1992 –2000 and additionally, 25 SLC images of ENVISAT ASAR from 2002 – 2010 acquired by ESA,, which cover the study area have been selected along this track

23. Repeated pass interferometry processing
Master image Slave image B┴ (m) Days

24. Coherence map for time interval 19980802–19980906 descending track
LARISA

25. Differential interferogram for time interval 19980802–19980906 descending track
LARISA

26. Interferometric stacking processing
Coherence map for time interval 1992–2010 descending track highlighting the coherence of reference point inside the red circle
LARISA

27. Ground deformation rates along LOS direction deduced by interferometric stacking, for the considered time intervals ( ), Bp 0-150, 73 inteferograms
LARISA

28. Persistent (Permanent) Scatterers Interferometry (PSI)
Distribution of geo-coded radar targets (persistent scatterers) in Larissa basin before expansion. The average in line of sight (LOS) velocity for the period (1992–2010) number of points are 1930
LARISA

29. Distribution of geo-coded radar targets (persistent scatterers) in Larissa basin after expansion. The average in line of sight (LOS) velocity for the period (1992–2010) number of points are 4801
LARISA

30. Chapter Three: Impact of groundwater on ground deformation
Location of groundwater monitoring network within study area, superimposed on SLC SAR image

31. Three point candidates of the PSI with different distances from borehole AD6 ASCENDING TRACK
Gap of data

32. LOS Displacemnt of point candidates of PSI corresponding to monthly precipitation amount. Displacement time series of point candidates are rescaled to the first acquisition (i.e. 28 June 1995). ASCENDING TRACK

33. LOS Displacemnt of point candidates corresponding to the groundwater level of borehole AD6. Displacement time series of point candidates are rescaled to the first acquisition (i.e. 28 June 1995). ASCENDING TRACK
There is no continuous significant correlation between deformation of this PSI point and groundwater level fluctuation for the borehole AD6. This may be attributable to the short time series (1995–2006)

34. Interferometric fringes
Conventional SAR Interferometry Seasonal Deformation – ASCENDING TRACK
Borehole
Groundwater level (m)
Interferometric fringes
SR72
20.62
Significant
SR77
18.50
High Significant

35. Interferometric fringes
Conventional SAR Interferometry Seasonal Deformation – DESCENDING TRACK 279
Borehole
Groundwater level (m)
Interferometric fringes
SR72
34.00
High Significant
SR77
36.43

36. Impact and interference type of clay minerals with fluctuation of groundwater level on land deformation
Rainfall
Groundwater withdrawal
Rising groundwater level
Decline of groundwater level
Presence of clay minerals which have the capability to swell and shrink
Water enters between clay layers
Water leaves from among mineral layers
Activation of swelling operation
Activation of shrinking operation
Subsidence of the ground
Uplift of the ground
Compression of materials
Maybe are caused microseismic (3–4) magnitude?

37. Chapter Four: Impact of faults movement and earthquakes on ground eformation
In order to examine and investigate the correlation between fault movements and ground deformation by implementing three techniques, conventional SAR interferometric, interferometric stacking and persistent scatterers interferometry (PSI),
Fault traces which are distributed within the study area of the eastern part of northern Thessaly were digitized from the papers by (Caputo, 1993), (Caputo and Pavlides, 1993), (Caputo et al., 1994), (Caputo et al., 2004), (Caputo and Helly, 2005) and (Caputo et al., 2006).
Thereafter these were corrected and rectified depending on 7 geological maps of Thessaly at a scale of 1:50,000 issued by the Greek Institute of Geology and Mineral Exploration, which were used along with field observations.
In addition, by using a seismotectonic map of Greece with seismogeological data at a scale of 1:500,000, a shape file was consequently created and identified utilizing GIS software ArcGIS 9.3.

38. Earthquake events data within the study area were collected by utilizing the earthquake catalogue of the (Institute of Geodynamics), National Observatory of Athens,
An attribute table was then created from this catalogue.
Consequently, a shape file of earthquake events was created utilizing Arc GIS 9.3 for the period 1964 – 2010 with magnitude M >= 3 and depth varying between 0 – 30 km.

39. Distribution of faults and earthquakes within study area

40. The interference effects of fault movement on ground deformation will be discussed and interpreted in a probability approach depending on spatial correlation, for the reason that no statistical correlation or model-building has been done between ground deformation and fault movement.

41. Ascending track 143 Interferometric stacking

42. Total deformation at Larissa estimated with interferometric stacking technique, June 1995-March 2008

43. Descending track 279 Interferometric stacking

44. Total deformation at Larissa estimated with interferometric stacking technique, November 1992 – October 2010

45. ASCENDING TRACK 1995 – 2006 Persistant Scatterers Interferometric (PSI)

46. Frequency of deformation rate of points targets at LARISA 1995-2006

47. Frequency of deformation rate of points targets at Tyrnavos 1995-2006

48. Frequency of deformation rate of points targets in Giannouli 1995-2006

49. Location of selected candidate points minimum and maximum deformation rate, ascending track 143, settlement of Larissa

50. Conventional SAR Interferometry ASCENDIGN TRACK SEASNAL DEFORMATION 19960228_19960403

51. Conventional interferogram corresponding to a 7 km cross-section of Larissa in the period _

52. Spatial profile showing the displacement field as observed by conventional interferometry within a 7 km cross-section of Larissa, in the period _ red lines correspond to the faults

53. Conventional SAR Interferometry DESCENDIG TRACK SEASNAL DEFORMATION 19980802_19980906

54. Conventional interferogram corresponding to 7 km cross-section of Larissa in the period _

55. Spatial profile showing the displacement field as observed by conventional interferometry within a 7 km cross-section of Larissa, in the period _ red lines correspond to the faults

56. Chapter Five: Impact of lithology types on ground deformation
The type of lithology has an important impact on ground deformation for the reason that any physical or chemical change of shape or size of materials will be reflected in the stability of objects.
Spatial correlation between lithology type and ground deformation has been created to verify the impact of lithology on ground deformation, taking into account the general type of lithology within the study area.
Thirty settlements were identified. However, just 19 were selected to examine and investigate the influence of lithology type on ground deformation.

57. The geological formations are grouped into three classes taking into account their lithology, consolidation, origin and age.
FIRST CLASS IS Alluvial = al
SECOND CLASS IS Fluvio-lacustrine deposits = Pt2
THIRD CLASS IS Terrestrial fluvio-torrential deposit = pl-pt

58. Geological map of Thessaly, map is modified from IGME
Geological map of Thessaly, map is modified from IGME. Faults are modified according of Caputo.

59. Ascending track 143 1995 - 2008 Interferometric Stacking
Minimum and maximum deformation rates in LOS of interferometric stacking of 19 settlements corresponding to type of lithology.
Alluvial = al
Fluvio-lacustrine deposits = Pt2
Terrestrial fluvio-torrential deposit = pl-pt

60. Descending track 279 1992- 2010 Interferometric Stacking
Minimum and maximum deformation rates in LOS of interferometric stacking of nineteen settlements corresponding to type of lithology.
Alluvial = al
Fluvio-lacustrine deposits = Pt2
Terrestrial fluvio-torrential deposit = pl-pt

61. Chapter Six: Impact of soil on ground deformation
The goal of this chapter is to examine the potential of using the PSI technique to identify the deformation of soil vertically (i.e., line of sight, LOS), and to study the statistical behavior of deformation for each point target through the statistical time series schemes of the data set, as well as the effect of soil type on its deformation.
According to the Exploratory Soil Survey and soil classification system (Soil Survey Staff, 1998) and (Soil Survey Staff, 1999), the classification of soil units of the study area (north part of Larissa) has been completed and 5 different orders were recognized (Alfisols, Entisols, Inceptisols, Mollisols, Vertisols)

62. The soil properties of each order have been examined, such as texture, drainage, erosion and slope. Soil data has been manipulated using Arc GIS 9.3 software, and several maps, such as soil texture, soil drainage, slope, and erosion have been created

63. Map of exploratory soil survey depicts the distribution of soil orders within the study area in the northern part of Larissa. Based on SLC of SAR image.

64. Ascending track 143
PSI candidate points within the non-urban area, mean displacement rates , ascending track 143. Movements are in the satellite line-of-sight direction. Based on SLC of SAR image.

65. Chapter Seven: The conclusions derived from this research study and Discussion
The data of SAR images ERS1/2 and ASAR ENVISAT which have been used in this research study are shown the possibility for investigating and identifying the temporal and spatial ground vertical movement within study areas of Larisa basin. However, the cons of these types of data were the spatial resolution which is 20 meters, consequently this spatial resolution does not was large enough to detect the ground deformation for objects which are located within large scale. However, the temporal resolution was applicable good enough to the objectives of this study.
The SAR interferometric conventional technique, has pros to investigate the ground deformation during short-term within urban and non-urban area. However, the cons of this technique are the deformation is limited by the atmospheric path delay term.

66. The SAR interferometric stacking technique has the advantages to bypass the cons of the atmospheric path delay, however no time series could be obtained for each single object by this technique.
The persistent scatterers technique has the advantages to obtain the ground deformation for each single object for long-term time series; however the disadvantage of this technique is the hard conditions ought to apply to get the candidates points specially within agricultural fields.

67. Approximately all correlation cases between fluctuation of groundwater level and land deformation point to non-continuous significant correlation through the short and long distances between boreholes and point candidates of PSI within ascending and descending tracks. This may be a reflection of the spatial complexity of aquifer systems, the variety of subsidence and uplift deformation, and the large number of illegal wells.
Significant interferometric fringes are observed within approximately all of the boreholes in two differential interferograms of two tracks, ascending and descending, through the fluctuation of groundwater level.
The Persistent Scatterers Technique, through the application of spatial correlation between the locations of points targets and fault traces, reveals or/and indicates the possibility of the influence of fault movements on ground deformation.

68. In spite of the controversy regarding the gap of the last large magnitude earthquake in Larissa (1941), which remains a major issue, nevertheless, fault movements, which are the main reason of earthquakes creation, may be attributed to the impact of mutual processes between the swelling and shrinkage of clay minerals.
SAR interferometry techniques successfully revealed the impact of lithology type on ground deformation through the ascending and descending tracks.
Subsidence could not be attributed to the sole impact of the type of lithology. This was because there are several nested and interconnected factors such as lithology, fault movements, type of clay minerals and amount of precipitation.

69. Papers have been published from the dissertation
Fakhri F, “Use Sar Interferometry DInSAR And PSI To Identify The Geohazard Risk Of Nato Airport North East Larissa (Central Greece) ” International Forum On Satellite Earth Observation For Geohazard Risk Management Santorini, May 2012.
Fakhri F, Parcharidis I, Karymbalis E, Pavlopoulos K, Relationship Between Lithology And Ground Deformation Estimated Using SAR Interferometry Over The Settlements Of Thessaly Prefecture (Central Greece). 4th Workshop On Remote Sensing And Geology Earsel Mykonos, Greece, 24 – 25 May 2012.
Fakhri F, Psomiadis Emmanouil, Parcharidis Issaak1 Monitoring Soil Deformation Using Persistent Scatters Interferometry (PSI) Technique: The Case Study Of Thessaly Prefecture (Central Greece) /12/ Ieee 3903 Igarss 2012
FAKHRI F, Investigating Of causes Short and Long Term Ground Deformation by Implementing SAR Interferometric Techniques in Larissa. ESA Living Planet Symposium September, 2013 Edinburgh, United Kingdom

70. THANK YOU FOR YOUR ATTENTION