Abstract
Abstract. We report a case study from the Po River plain region (northern Italy), where significant liquefaction-related land and property damage occurred during the 2012 Emilia seismic sequence. We took advantage of a 1 m pixel lidar digital terrain model (DTM) and of the 2012 Emilia coseismic liquefaction data set to (a) perform a detailed geomorphological study of the Po River plain area and (b) quantitatively define the liquefaction susceptibility of the geomorphologic features that experienced different abundance of liquefaction. One main finding is that linear topographic highs of fluvial origin – together with crevasse splays, abandoned riverbeds and very young land reclamation areas – acted as a preferential location for the occurrence of liquefaction phenomena. Moreover, we quantitatively defined a hierarchy in terms of liquefaction susceptibility for an ideal fluvial environment. We observed that a very high liquefaction susceptibility is found in coincidence with fluvial landforms, a high-to-moderate liquefaction susceptibility within a buffer distance of 100 and 200 m from mapped fluvial landforms and a low liquefaction susceptibility outside fluvial landforms and relative buffer areas. Lidar data allowed a significant improvement in mapping with respect to conventionally available topographic data and/or aerial imagery. These results have significant implications for accurate hazard and risk assessment as well as for land-use planning. We propose a simple geomorphological approach for liquefaction susceptibility estimation. Our findings can be applied to areas beyond Emilia that are characterized by similar fluvial-dominated environments and prone to significant seismic hazard.
Highlights
Soil liquefaction is one of the most outstanding hydrogeological processes that can occur during earthquakes, provided the existence of saturated loose sandy layers confined by impermeable deposits within a certain distance from the earthquake epicenter
In order to find a simple and homogeneous approach to define areas characterized by different liquefaction potential, we performed a quantitative analysis of the spatial distribution of the 2012 coseismic liquefaction effects using GIS tools
Among the liquefactions observed on mapped fluvial landforms, alluvial ridges and levee ridges hosted 63 % of the observed liquefaction effects, while crevasse splays account for 20 % and abandoned riverbeds for 17 % (Fig. 7)
Summary
Soil liquefaction is one of the most outstanding hydrogeological processes that can occur during earthquakes, provided the existence of saturated loose sandy layers confined by impermeable deposits within a certain distance from the earthquake epicenter. Liquefaction phenomena are responsible for significant damage to lifelines, infrastructure, agricultural lands and properties, as recently highlighted by the 2010–2011 Canterbury earthquake sequence in New Zealand (van Ballegooy et al, 2014) and by the 2012 Emilia earthquake sequence in the Po Plain, northern Italy (EMERGEO Working Group, 2013). The assessment of liquefaction susceptibility in fluvial and coastal plains is a worldwide topic that is growing in interest, probably because of the recent need for “new” areas for urban and industrial development related to the fast growing of global population.
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