Persistent Scatterer Interferometry（ PSI） is widely used to monitor the slowly accumulated land subsidence in urban areas. However

a few explorations concentrated on monitoring the significant subsidence by PSI and its applicability in such areas.In this study

typical industrial towns（ subsidence troughs） located around the boundary between Tianjin and Langfang cities were chosen as the study areas for subsidence detection and analysis with multiband Synthetic Aperture Radar（ SAR） images to evaluate the potential and applicability of PSI to monitor significant ground subsidence. Land subsidence was extracted using PSI through phase spatial correlation analysis and three dimensional phase-unwrapping approaches. In total

23 L-band（ wavelength is23. 6 cm） Phased Array type L-band Synthetic Aperture Radar（ PALSAR） images acquired between 2007 and 2010

and 23C-band（ wavelength of 5. 6 cm） Advanced Synthetic Aperture Radar（ ASAR） images acquired between 2007 and 2009 were selected for multiband data processing. The results derived from the two types of SAR images were comprehensively and mutually compared and validated. In addition

the reliability of the PSI method for significant subsidence detection was explored by considering the different sensitivities to subsidence of the PALSAR and ASAR systems. The spatiotemporal distribution of the subsidence in the study area was also analyzed with respect to the geological settings and groundwater exploitation information. The derived subsidence in the study area presents a significant inhomogeneous pattern

and the subsidence trend derived from the two types of SAR images ranges between 0 and 210 mm / a. The root mean squared error is 6. 5 mm / a between the two types of PSI subsidence results in the subsidence bowl area. Further exploitation indicates that such significant subsidence is mainly caused by excessive exploitation of groundwater. Moreover

the subsidence magnitude is highly related to different land-use categories

such as factories

residential quarters

railways

highways

and farmland

indicating anisotropy of groundwater usage in these areas. Comparison analysis demonstrates that the PALSAR and ASAR PSI results are in good agreement and are consistent with previous studies

although the two data sets have different spatial and temporal resolutions

wavelengths

incidence angles

and time spans. The above results and analysis indicate that the PSI method used in our experiment is applicable to different SAR systems. The PSI method shows good reliability and applicability to monitor long-term significant ground subsidence in areas with sparse PS distributions. Therefore

the PSI method used in this study can provide scientific and effective technical assistance for ground subsidence monitoring in such areas. The results（ subsidence rate and time series） of the PSI method can serve as assistant information when constituting measures to control groundwater exploitation.