Monitoring of mining-induced land subsidence by PALSAR and TerraSAR-X

In this study, we applied InSAR time series analysis using PALSAR and TerraSAR-X data to Zonguldak Hardcoal Basin in Republic of Turkey in order to monitor mining induced surface displacement. Zonguldak coal area is located along the Black Sea 240 km eastward from Istanbul. Recently, ground deformation caused by underground exploration has come to the surface, and it has been destroying roads and buildings. We utilized PALSAR and TerraSAR-X data for the detail analysis on the recent land subsidence induced by mining activities. PALSAR data in the fine beam mode were obtained from an ascending orbit, TerraSAR-X data in the StripMap mode were from a descending orbit. The vertical and the east-west displacement were calculated by the composition of the deformation vectors of PALSAR and TerraSAR-X. Additionally, the source depth of the main anomaly detected near the campus of Zonguldak Karaelmas University (ZKU) was estimated by vector analysis using the vertical and east-west displacement. As a result, it was approximately 80 to 100 meters under the sea level. On the other hand, the depth of coal production zones is recorded 300 to 560 meters under the sea level. Thus, it was supposed that the anomaly near the university had been caused by not only mining activities but also the other factor in the shallower geological formation. Because some historical documents said that some caves existed in the limestone formation bedded over coal formations and domestic wastewater is injected into these caves, perhaps the cause of land subsidence is considered the expansion of caves’ space resulted from the solution of limestone rocks by the wastewater injection.