GMES Terrafirma II Stassfurt Case Study - Preliminary Results -

Transcription

1 GMES Terrafirma II Stassfurt Case Study - Preliminary Results - Presenter: Kai Hahne Author: Friedrich Kuehn BGR/Germany kai.hahne@bgr.de friedrich.kuehn@bgr.de PSI-Processing by DLR Oberpfaffenhofen/Germany

2 The Study Area: - The Stassfurt/Bernburg site lies south of Magdeburg in the German Federal state of Saxony-Anhalt. - The entire area is characterized by numerous abandoned underground mines. - Abandoned lignite mines vary in depth from about 30 to 100 m. Potash was mined at depths of 200 to 600 m. Magdeburg - Lignite mining was shut down in the 1950s; mine galleries collapsed, resulting in collapse sinkholes and land subsidence. - Potash mining ran out in the 70ties; mines were flooded. Due to mine convergence and subrosion large-scale land subsidence and collapse sinkholes have been formed. Stassfurt Bernburg

3 Bernburg Oblique aerial photograph by F. Kuehn, BGR Stassfurt Town Land Subsidence Land Subsidence Land Subsidence Collapse Sinkhole Stassfurt Study Area: Large-scale mining activities of the past have left tailings dumps and abandoned mines. Lakes occupy areas of subsidence. Sinkholes result from collapsed mines. The sinkhole left of tailings dump was formed by collapse of a potash mine. Further collapse-prone ground exists NW and SE.

4 Stassfurt: Simplified vertical section explaining formation of land subsidence and collapse sinkholes at the flanks of the rock salt diapir: SW Land subsidence NE Overburden Mass movement Land subsidence marker (4.5 m level) Historic town center is ground water lake now. Rock Salt Abandoned mines flooded and subject to convergence Buildings, severely damaged by land subsidence.

5 Extract of Processing Report (DLR): Process Date: December 14, 2006 Software used: PSI-GENESIS Number of scenes used: 84 Date range of analysis: April 29, September 17, 2005 Satellite data used: ERS-1/2 and ENVISAT-ASAR Master Scene Date: March 28, 1998 Projection system used: UTM, Zone 32N, WGS84 Reference point location: Easting: m; Northing: m Area of results: Easting: m m; Northing: m m Number of PS identified: 6112 (coherence > 0.42) PS density (PS/km 2 ): 2.8 Point motion statistics (mm/yr classes) of points in each mm/year class -max to -3.5: 2.6 % -3.5 to -1.5: 7.5 % -1.5 to +1.5: 89.1 % +1.5 to +3.5: 0.8 % +3.5 to +max: 0.0 %

6 Stassfurt Bernburg Section of Landsat 7 Pan image with classified PS-points (C>0.42).

7 Section of Geological Map Mined subsurface space Potash horizon at -325 m NN Enlarged section of Landsat 7 Pan image with classified PS-points (C>0.42), layout of former potash horizons at -325 m NN (blue) and mined subsurface space (yellow) according to geological map (above).

8 Copyright Airphotos: Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR) Persistent-scatterer-cluster formed by 5 single points representing area of maximum land subsidence in Stassfurt (above/right): - Average velocity at points of cluster: mm/year - Single point of max. motion: mm/year (in circle).

9 Bernburg area (add-on test site) Stassfurt Geological section west of Bernburg A B Rock salt Salt mining area Ilberstedt (active) B Bernburg Carnallite seam (potash) Rock salt and potash are subject to mining Potash mining area Aderstedt (abandoned) ESCO rock salt mining area (abandoned) A Classified PSI data on Landsat 7 (Pan) image

10 Point of maximum ground motion with mm/year ( ) Bernburg Study Area Aderstedt area Bernburg/ South Copyright Airphoto: Landesamt fuer Geologie und Bergwesen (LGEB), Saxony-Anhalt ESCO Mine Plant

11 Bernburg/West (Aderstedt): Land subsidence due to abandoned potash mine field at west of Bernburg. Picture Copyright Airphoto: Landesamt fuer Geologie und Bergwesen (LGEB), Saxony-Anhalt Persistent-scatterer-cluster formed by 7 points representing large area of extreme land subsidence west of Bernburg (Aderstedt): - Average velocity at points of cluster: mm/year - Single points of max. motion: and mm/year (circle). Area of subsidence

12 200 m Bernburg/South: Land subsidence caused by abandoned rock salt mine: Asymmetric motion affecting department store (1992 to 2005 data): Cluster 1: -31 cm total motion Cluster 1 Cluster 2: -22 cm total motion Cluster 2 Difference - east/west wing: 9 cm mm/y Cluster 1 Copyright Airphoto: Landesamt fuer Geologie und Bergwesen (LGEB), Saxony-Anhalt Persistent-scatterer-clusters formed by 5 and 3 points on departments store north of abandoned "ESCO Rock Salt Mine": Cluster 2 - Average velocity at points of cluster 1: mm/y, - Average velocity at points of cluster 2: mm/y.

13 Summary: - PSI proved to be efficient tool for ground motion detection even if its rate amounts to parts of a mm per year. - In Stassfurt and Bernburg recent land subsidence could be detected for areas of abandoned potash and rock salt mine convergence, areas of active rock salt mining. - PSI-results high-reliably correspond with geological setting and ground-based leveling data. Further issues to consider: - East Germany was subject to strong socio-economic impact after > Deconstruction and restoration of industrial plants and mining sites, > Restoration of settling areas, > Strong influence on stability of persistent scatterers over long periods, > Shorter time series required (new processing for 1995 to 2000?). General conclusion: - Due to good experience with GMES/Terrafirma projects, BGR is going to utilize PSI for further projects (technical cooperation, underground storage issues, etc.).

14 Thanks to: - Landesamt für Geologie und Bergbau (State Authority for Geology and Mining) of the Germany Federal State of Saxony-Anhalt - Partners of the research project Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks (Dynamics of flooded salt mines and their overburden rocks) for support with ground truth data, advice and discussion.