A framework for probabilistic seismic risk assessment of NG distribution networks

Lifelines are essential infrastructures for human activities and the economic developm ent of a region. Lifelines vulnerability reduction is an actual question, particularly with reference to NaTech events, like earthquakes. In this regard, worldwide past seismic experiences revealed heavy damages to NG distribution networks. It is therefore essential to perform seismic risk assessment of NG buried pipelines systems with the aim to identify potential criticalities and avoid significant consequences. For such reasons, this work illustrates the proposal of a probabilistic framework for seismic risk assessment of NG lifelines. The proposed procedure is subsequently applied to a specific case study in Italy to highlight its feasibility

Seismic Risk Assessment Tools Workshop

Held in the European Crisis Management Laboratory on 11-12 May 2017, the Workshop brought together on one side the developers of some of the most widely used modern seismic risk assessment tools and on the other a number of Civil Protection authorities from countries of the European Civil Protection Mechanism. The objective was to demonstrate the use and capabilities of the tools, explore the possible use in near-real-time impact assessment and promote their use in risk planning and disaster response. The systems presented in the workshop demonstrated a very high sophistication and increased flexibility in accepting data from a large number of sources and formats. Systems that were initially developed on a national scale can now work on a global level with little effort and the use of global-scale exposure data is almost seamless. An urgent need for more accurate exposure data being openly available was identified, as well as the need of proper use of the fragility curves. Inter-system collaboration and interoperability in some cases to increase ease of use was greatly appreciated and encouraged. All systems participated in a real-time simulation exercise on previously unknown seismic data provided by the JRC; some additional automation might be in order, but in general all systems demostrated a capacity to produce results on a near-real-time basis. The demonstrations were unanimously welcomed as very useful by the participating Civil Protection Authorities, most of which are either using a locally-developed system of moving towards using one of those presented in the workshop.JRC.E.1-Disaster Risk Managemen

Seismic Risk Assessment in the Attica Basin

This paper aims to determine the exposure-based earthquake risk posed in the Attica Basin, Greece using a GIS based methodology. The hazard level is based on grouped geological formations according to the New Ground Anti-Earthquake Regulation of Greece and the structural setting of the area. Vulnerability is calculated using two different methodologies. The first one uses a deterministic approach by attributing population values to each building block divided by the of each municipality and the second one uses a probabilistic approach by using centroids based on a building block level and then creating their kernel density. Both of these approaches are combined with land use maps to create the final vulnerability layers. Risk is calculated in two ways, using the product and a weighted overlay of the hazard and vulnerability layers. In the Risk maps, proof of concept comes from overlaying the damages from the earthquakes of 1981 and 1999 that affected Attica Basin. Moreover, both the maps show high Risk probability in the area of the east part of the Attica Basin but without significant damages from past earthquakes. This suggests that the Kifisos Fault Zone might act as a seismic barrier depending of the location of the epicentre

Seismic reliability assessment of classical columns subjected to near-fault ground motions

A methodology for the performance-based seismic risk assessment of classical columns is presented. Despite their apparent instability, classical columns are, in general, earthquake resistant, as proven from the fact that many classical monuments have survived many strong earthquakes over the centuries. Nevertheless, the quantitative assessment of their reliability and the understanding of their dynamic behavior are not easy, because of the fundamental nonlinear character and the sensitivity of their response. In this paper, a seismic risk assessment is performed for a multidrum column using Monte Carlo simulation with synthetic ground motions. The ground motions adopted contain a high- and low-frequency component, combining the stochastic method, and a simple analytical pulse model to simulate the directivity pulse contained in near source ground motions. The deterministic model for the numerical analysis of the system is three-dimensional and is based on the Discrete Element Method. Fragility curves are produced conditional on magnitude and distance from the fault and also on scalar intensity measures for two engineering demand parameters, one concerning the intensity of the response during the ground shaking and the other the residual deformation of the column. Three performance levels are assigned to each engineering demand parameter. Fragility analysis demonstrated some of the salient features of these spinal systems under near-fault seismic excitations, as for example, their decreased vulnerability for very strong earthquakes of magnitude 7 or larger. The analysis provides useful results regarding the seismic reliability of classical monuments and decision making during restoration process

Integral seismic risk assessment through fuzzy models

The usage of indicators as constituent parts of composite indices is an extended practice in many fields of knowledge. Even if rigorous statistical analyses are implemented, many of the methodologies follow simple arithmetic assumptions to aggregate indicators to build an index. One of the consequences of such assumptions can be the concealment of the influence of some of the composite index’s components. We developed a fuzzy method that aggregates indicators using non-linear methods and, in this paper, compare it to a well-known example in the field of risk assessment, called Moncho’s equation, which combines physical and social components and uses a linear aggregation method to estimate a level of seismic risk. By comparing the spatial pattern of the risk level obtained from these two methodologies, we were able to evaluate to what extent a fuzzy approach allows a more realistic representation of how social vulnerability levels might shape the seismic risk panorama in an urban environment. We found that, in some cases, this approach can lead to risk level values that are up to 80% greater than those obtained using a linear aggregation method for the same areas.Peer ReviewedPostprint (published version