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Earthquake early warning (EEW) constitute a major tool for seismic resilience enhancement in modern societies, helping mitigate some of the devastating effects of earthquakes (e.g., deaths, business interruption) in the face of increasing exposure and vulnerability to seismic events worldwide. However, traditional EEW approaches (such as feasibility studies and decision-making related to triggering alerts by different end users) are essentially based on seismological considerations.In this study, jointly developed with the University College London in the framework of the EU H2020 TURNkey Project (https://earthquake-turnkey.eu/), we adopt a risk-based approach to EEW. We present the results of a state-of-the-art feasibility study for EEW in schools performed across the Patras region of Greece, which combines traditional seismologically-driven EEW decision criteria (warning time) with proxy risk-oriented measures for earthquake impact (building fragility and the number of exposed students). The results, showing the effectiveness of EEW under certain conditions, are the premises for the demonstration of an innovative end-user-centred approach for improved risk-informed decision-making on triggering EEW alerts, which merges earthquake-engineering-related seismic performance assessment procedures and metrics with multi-criteria decision-making within an end-to-end probabilistic framework. The approach, demonstrated using an archetype school building for the case-study region, emphasizes that the best action (i.e., “trigger” or “don’t trigger” an EEW alert) for a given level of ground shaking depends on the stakeholder preferences towards the predicted damage/loss estimates consequences., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Deliverable from WP3 of TURNkey project

Deliverable from WP3 of TURNkey project

This report details the procedures that have been applied, developed or improved in Task 3.4 for the rapid generation of ground shaking maps (i.e., shake-maps). The report revolves around several actions and technical results, which are organized as follows:  Section 3 summarizes the state-of-the-art of current shake-map algorithms and systems, based on a review by Guérin-Marthe et al. (2021). The USGS ShakeMap v4 approach is compared to a method based on Bayesian updating, which is put forward as one of the technical solutions to be implemented in the TURNkey platform.  Section 4 is based on previous work carried out in Task 3.3.2: in each TB, various GMMs (Ground-Motion Models) are evaluated and ranked, via different scoring metrics. The selected GMMs may then be used for the generation of shake-maps in each TB.  Section 5 details novel research efforts, where the GMM coefficients are updated in order to match the observations. This approach is useful to rapidly update a GMM in a given area for a given earthquake, so that the updated GMM may be reused for subsequent events (e.g., in a seismic sequence) in order to improve the accuracy of ground-shaking estimates. Two parallel and complementary methods are presented, namely a direct calibration of the coefficients (EUC) and a Bayesian updating of the uncertain coefficients in the shake-map (BRGM).  Section 6 discusses site amplification models that are available in each TB: besides local models, Vs30 maps generated at the European level (in the European project SERA) are extracted for each TB. Recommendations are given for each TB on which model should be applied, and whether the SERA model represents a satisfying approximation.  Section 7 explores additional sources of observations that may be used to characterise shake-maps: collection and aggregation of felt reports by EMSC; and extraction of Twitter data and integration as soft evidence in the shake-maps by BRGM. The Bayesian approach for the derivation of shake-maps has been implemented in a Python code, which is briefly described in the companion deliverable report D3.9.

Proceedingsof the XXV Conferenza Geotecnica di Torino ,CGT,Torino (Italy),November 2018.

On May 20, 2012, a seismic event of moment magnitude MW = 6.1 hit and caused severe damage on a large area in the river Po Valley, located in the northern Italy. This earthquake was characterized by extensive occurrence of soil liquefaction and basin effects lying over deep deposits. Within the scope of the European research project titled LIQUEFACT, a reference site located in the countryside near the hamlet of Pieve di Cento (at the boundary of the province of Bologna towards Ferrara) was selected as a trial field in order to assess the effectiveness of several mitigation measures against liquefaction. As a first step of the task, this paper presents the geotechnical model of the site based on in-situ investigations and pre-existing geological studies, which allowed to locate the bedrock depth. As a second step, representative input motions for the LIQUEFACT project were selected aiming at simulating the 20.V.2012 seismic event as well as three possible future scenarios with an increasing level of seismic intensity. Finally, preliminary dynamic analyses are presented, that reproduce the observed liquefaction triggering after the 2012 main event and predict the seismic soil response at the test site.&nbsp

A significant seasonal modulation of seismicity, with a peak in spring and summer, is evidenced in the Himalaya and the Alps, two regions characterized by present day mountain building and glacial retreat. In addition, a secular modulation of seismicity, which can be correlated with surface atmospheric temperature changes in the Northern Hemisphere, is found over the last ten centuries. Therefore, secular variations in permanent glacial dimensions, naturally associated with long-term average surface atmospheric temperature changes, and seasonal snow load may cause crustal deformations that modulate seismicity.

È stato affrontato il problema della definizione della pericolosità sismica (input sismico) tramite la modellazione dei possibili scenari compatibili con la storia sismica e la sismotettonica della zona di Nimis. I sismogrammi sintetici, che tengono conto dei principi fondamentali della fisica relativi alla generazione e propagazione delle onde sismiche, consentono di colmare le lacune nei dati, inevitabilmente incompleti a causa della limitata finestra temporale coperta dalle osservazioni, rispetto ai tempi dei processi geologici causa dei terremoti. L’elevata sismicità della zona rende complessa la realizzazione di strutture resi- denziali utilizzando tecniche antisismiche tradizionali, mentre risulta particolarmente vantaggioso l’impiego di tecniche avanzate, quali l’isolamento sismico, che consente, nell’ambito della normativa vigente, la realizzazione di costruzioni con interessanti soluzioni architettoniche.

North Africa is one of the most earthquake-prone areas of the Mediterranean. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss of life and considerable economic damage to the region. In order to mitigate the destructive impact of the earthquakes, the regional seismic hazard in North Africa is assessed using the neo-deterministic, multi-scenario methodology (NDSHA) based on the computation of synthetic seismograms, using the modal summation technique, at a regular grid of 0.2 × 0.2°. This is the first study aimed at producing NDSHA maps of North Africa including five countries: Morocco, Algeria, Tunisia, Libya, and Egypt. The key input data for the NDSHA algorithm are earthquake sources, seismotectonic zonation, and structural models. In the preparation of the input data, it has been really important to go beyond the national borders and to adopt a coherent strategy all over the area. Thanks to the collaborative efforts of the teams involved, it has been possible to properly merge the earthquake catalogues available for each country to define with homogeneous criteria the seismogenic zones, the characteristic focal mechanism associated with each of them, and the structural models used to model wave propagation from the sources to the sites. As a result, reliable seismic hazard maps are produced in terms of maximum displacement (D max), maximum velocity (V max), and design ground acceleration.

Estimates of seismic hazard obtained using the neo-deterministic approach (NDSHA) and the probabilistic approach (PSHA) are compared for the Italian territory. The NDSHA provides values larger than those given by the PSHA in areas where large earthquakes are observed and in areas identified as prone to large earthquakes, but lower values in low-seismicity areas. These differences suggest the adoption of the flexible, robust and physically sound NDSHA approach to overcome the proven shortcomings of PSHA, thus allowing for a reliable seismic hazard estimation, especially for those areas characterized by a prolonged quiescence, i.e. in tectonically active sites where events of only moderate size have occurred in historical times.