Mapping the susceptibility of earthquake-induced soil liquefaction at the continental scale is a challenge. Susceptibility of soils to liquefaction is the tendency of certain geomaterials to undergo a severe stiffness degradation and loss of shear strength. The latter could be induced by cyclic loading induced by seismic events. The liquefaction surface evidence is a local phenomenon, and detailed geotechnical field investigations are not available for regional studies, not to mention at continental scales. The literature review shows earthquake-induced soil liquefaction evidence in several European countries, yet, a comprehensive picture of the susceptibility at the European scale is not available. This work aims to develop a methodology to assess the earthquake-induced soil liquefaction susceptibility in Europe using geospatial parameters weighted via the Analytic Hierarchy Process (AHP). The major outcome of the study is a novel Liquefaction Susceptibility map of Europe (LSE), based on the building of ten different European macro-units for earthquake-induced soil liquefaction. These European macro-units have been delineated in this work in order to be homogenous areas from the geological, physiographical, and geomorphological points of view. The adopted input parameters are the depositional environment of the sediments, the distance from water bodies (coast and rivers), and the compound topographic index (as a proxy of the soil saturation). The resolution of the LSE map is 900 × 900 m. The results have been cross-compared with soil liquefaction susceptibility maps available for a region of Greece (i.e. Thrace), Portugal, Bulgaria, and sites where liquefaction manifestations occurred across Europe. The LSE can be adopted to identify at large scale the areas susceptible to liquefaction including also the territories across Europe characterized by low seismicity and potentially affected by anthropogenic seismicity.
Microzonation for earthquake-induced liquefaction hazard is the subdivision of a territory at a municipal or submunicipal scale in areas characterized by the same probability of liquefaction manifestation for the occurrence of an earthquake of specified intensity.The liquefaction hazard at a site depends on the severity of expected ground shaking as well as on the susceptibility to liquefaction of that site. This in turn depends on geological, geomorphological, hydrogeological and geotechnical predisposing factors. Thus, liquefaction hazard implies the existence of territories characterized by a moderate to high level of intensity of expected ground shaking. Microzonation charts for ground shaking and liquefaction hazard play a key role for the mitigation of seismic risk of an urban centre as they provide a valuable tool for the implementation of prevention strategies and land use planning. The LIQUEFACT project fully addressed the problem of microzoning a territory for earthquake-induced liquefaction hazard in a specific work package. Four municipal testing areas were selected across Europe as peculiar case studies where to construct microzonation charts for earthquake-induced liquefaction hazard. They are located in Emilia-Romagna region (Italy), Lisbon metropolitan area (Portugal), Brežice territory (Slovenia) and Marmara region (Turkey). Their location was identified based on the following criteria: severity of expected seismic hazard, availability of geological and geotechnical data, presence of liquefiable soil deposits, documented cases of liquefaction manifestations occurred in historical earthquakes, representativeness of different geological settings, density of population in selected areas (exposure). This paper illustrates the general procedure developed in LIQUEFACT for the assessment of earthquake-induced liquefaction hazard at urban scale and presents the main achievements of the microzonation studies carried out at the four previously mentioned European testbeds. Since the microzonation studies have been carried out using a shared framework and methodology, this paper has the ambition to serve as technical guidelines for updating the standards and the operational criteria currently used in different countries worldwide to construct seismic microzonation maps of liquefaction hazard. Keywords Liquefaction • Earthquake • Microzonation • Guidelines • LIQUEFACT projectsite-specific geotechnical investigations with pre-existing geological and geotechnical data from public and private sources.Existing information on quaternary deposits and man-made landfills, geomorphological maps, trench pits, boreholes and piezometric monitoring data, shall be stored and analysed in a georeferenced (GIS) environment to identify homogeneous lithostratigraphic units susceptible to liquefaction. These data shall be complemented with field and laboratory geotechnical and geophysical information from pre-existing investigation campaigns. This will eventually allow to plan and implement the complementary experimental investi...
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