The medium-to long-term effects of soil liquefaction in the po plain (Italy)

The 2012 Emilia seismic sequence has shed light on some unusual geomorphological processes and related landforms observed in the Po Plain between the provinces of Modena and Bologna, namely small-scale sinkhole formation, in a non-karstic setting. In some of the areas previously affected by sinkholes, during the Emilia earthquakes, widespread coseismic effects were observed, as soil liquefaction, sand venting and ground cracks. Before 2012, these effects have been seldom observed in the Po Plain, mainly because of moderate seismicity. Known historical earthquakes, or eventually older events, could have been the original triggering factor of liquefaction of susceptible soils at shallow depth and formation of dikes and sills, as precursors of future sinkholes. To test this model, data collection on boundary conditions and a number of further field experiments is ongoing. In particular, the research is focused on three main issues: the setup of a geological model of the area, taking into account structural a tectonic features; the analysis of surface displacements horizontal (geodynamic) and vertical displacements (natural and/or artificial subsidence) and their relationships with the development of sinkholes. This is performed through the exploitation of SAR interferometric data and GPS data; geological and geotechnical characterization of soils, through a number of continuous boreholes, trenches and CPT tests for building cross sections and 3D models of areas prone to sinkhole development. These pieces of information are used for set up a numerical model and simulating the process of sinkhole triggering ad evolution in the River Po alluvial plain.