The study area is located to the north of the Carpathian mountain range, in the central part of the Upper Silesian Coal Basin (USCB), in southern Poland. The USCB basin forms the western part of the Silesia-Cracow Upland and peripherial part of the Silesian Beskids. It is bounded by line Ostrava-Tarnowskie Góry-Skawina-Ostrava. The south-west part of the Basin extends into Czech Republic, where it occupies the Ostrava and Karvina mining areas. It covers an area of about 5000 km2. This foredeep consist of Carboniferous molasse developed on the Precambrian block of the Upper Silesian Massif. Cambrian, Devonian and Carboniferous rocks were recorded. Carboniferous rocks continuously overlie Devonian deposits. The profile includes the top of the pre-flysch carbonate association, marine clastic sediments that correspond to the flysch succession 1000 m thick as well as the coal-bearing molasse of a foredeep depression. Lower Carboniferous deposits of the carbonate association do not have an established lithostratigraphic division whereas Upper Visean and Lower Serpukhovian marine clastic deposits have been classified into two lithostratigraphic units of a formation rank. The Upper Carboniferous coal-bearing sequence has been divided into lithostratigraphic units of different rank but they are not defined according to the principles of the stratigraphic code. Four lithostratigraphic series have been distinguished as follows: the Paralic Series, the Upper Silesian Sandstone Series, the Mudstone Series and Cracow Sandstone Series. The pattern of coal quality zones in the USCB does not correspond to principal stratigraphical boundaries as well as main geological structures.
Coal mining activity in the USCB has been conducted since the 17th century. In 1979 the largest amount of coal 200x10 Mg/year was mined. At present there are 30 active coal mines in the USCB. Total exploitation of coal is estimated at 70x106 Mg/year. In the study area, hazardous ground deformations are caused primarily by the extensive and longwall mining operations, chiefly in the vicinities of the cities of Katowice, Zabrze and Ruda Slaska. The subsidence in Upper Silesia reaches velocities commonly of a few centimeters per month but there are many areas with subsidence of one centimeter daily.
Exploitation of coal deposits, conducted in the USCB for over 200 years, has created a complicated state of stress and deformation, which is the cause of dynamic phenomena manifested in the form of rock mass shock. Systematic seismic observations have been here for about 60 years. Currently, Central Mining Institute conducts and develops bank "of strong mining tremors" on the basis of data sent by the Upper Silesian Regional seismic network (GRSS) and mining seismological network (KSS).
The level of induced recorded seismic intensity is very diverse and ranges from weak to strong shocks that cause damage.
Places indicating increased mobility of the substrate should be strictly taken into account during the mining activities and the development of spatial plans. Areas that should be surveyed in the first place, are the Halemba coal mine district, adjacent to the Klodnicki fault, area of KWK Murcki designated by lines of fault: Klodnicki (north), Wojciech (east) and unnamed (west) in the form of a wedge zones, faults in the region KWK Sobieski - Jaworzno III, and the entire zone of Bedzinski fault.
Katowice, Poland test site
In DORIS project two types of SAR processing were used: Differential Interferometry (DInSAR) and Permanent Scatterer Interferometry (PSI) inlucding new SqueeSARTM algorithm. InSAR data used for the analysis in Upper Silesian Coal Basin:
- ERS PS dataset 1992-2001 and one interferogram 1997/10/22-1997/12/31
- ENVISAT PS dataset 2003-2010 and one intergerogram 2007/02/07-2007/04/18
- ALOS-PALSAR 5 interferograms from Terrafirma project - period 2007/02-2008/05 with time span 45 or 92 days
- TerraSAR-X PS dataset - period 2011/07/05-2012/06/12
- TerraSAR-X 28 interferograms - period 2011/07/05-2012/06/12 with time span 11 days
The best method for monitoring big surface deformation cause by mining activities was DInSAR of L band (interferograms from ALOS satellite) and X–band satellites (interferograms from TerraSAR-X). This technique is able to detect surface deformations in the range of several decimetres per year.
On the other hand PSI technique from ERS and ENVISAT satellites very well illustrate subsidence occurring in the abandon and active mining areas where subsidence does not exceed 40 mm/yr. The comparison of the PSI data set from various bands is presented in Fig. 1. X-band PSI dataset is significantly bigger than C-band dataset (even 10 times more PS). C-band data illustrate rather general trend, whereas X-band can be used for single basin analysis.
Lack of points in areas of fast ground motions was supplemented by the use of differential interferograms. Areas with subsidence greater than 100 mm/yr have been detected. Example of complementarity of the data can be seen on Fig. 2, were fringes from interferograms are presented as polygons and are located in the “holes” of PSI dataset. The time series graph correspond to the fringes visibility. When the fringe show up in October, PS points near it show stability in earlier months and the subsidence trend after October.
On the basis of this analysis Doris products were created. In the Fig. 3 is presented Ground deformation velocity map by Envisat satellite SAR data. In the Fig. 4 is presented example of Damage assessment map, where are visible areas predicted to be covered by the greatest risk of damage.
Fig 1: Example of PSI datasets obtain from various satellites.
Fig 2: Example of complementarity of the PSI and interferograms from TerraSAR-X satellite.
Fig 3: Ground deformation velocity map by Envisat satellite SAR data.
Fig 4: Example of Damage assessment map in Ruda Slaska area.
A highland in southern Poland located between the upper Vistula and the upper Oder rivers.
Land subsidence, and related hazards, caused by coal mining activities.