SI helps to map relative susceptibility to ground and slope instabilities in the Lanzhou loess area of Gansu Province, China

The PSI (Persistent Scatterer Interferometry) processing of ENVISAT ASAR data (period 2003-2010) provided spatially dense information (more than 400 PS/km2) on ground surface displacements in Lanzhou, capital of Gansu Province, NW China. The geomorphological and geological context of the local Yellow River valley indicate that the lower, flat areas with floodplain and valley-fill deposits (Holocene terraces with mainly reworked loess at the surface) are stable, whereas some higher, gently sloping valley sides appear locally unstable, particularly where the Late Pleistocene terraces are covered by young aeolian (Malan) loess. The PS velocity data suggest that the relative susceptibility to ground and slope instabilities is the highest on the 4th and 5th order river terraces. This is consistent with the presence of collapsible Malan loess and recent land use of these terraces involving irrigation and construction.