Insights into spatially correlated ground motion intensity measures using Italian earthquakes

Modelling the spatial correlation of ground motion intensity measures (IMs) has become a keystone in seismic hazard and risk analysis of portfolios of buildings, spatially distributed infrastructures and earthquake-induced phenomena. The quantification of the seismic performance of such systems over a region requires knowledge of the joint probability of occurrence of different ground motion IMs at multiple locations. Therefore, the classical Probabilistic Seismic Hazard Assessment (PSHA) tools, which are based on the hypothesis of independency between IMs at closely spaced sites, are not appropriate. Over the past decade, the spatial correlation of peak ground acceleration (PGA) and spectral acceleration (SA) has been widely studied. Although common findings suggest that the correlation of intra-event residuals decreases quite rapidly with increasing separation distances, these models feature different rates of decay. Among the causes that may lead to inconsistencies between models, with significant impact on hazard and loss estimates, are the multiple techniques used to estimate the correlation structure, the region and local site conditions, as well as the choice of the databases. Furthermore, little effort has been directed towards other IMs suitable to characterize the resulting damage to structures and predict ground failure: peak ground velocity (PGV), peak ground displacement (PGD) and spectral displacement (SD) as well as Arias intensity (퐼") and cumulative absolute velocity (CAV), to name but a few. A proper definition of the seismic action in terms of spectral displacement ordinates has progressively gained importance in performance-based seismic design, and 퐼" and CAV have been found to be adequate for many other earthquake engineering applications, such as evaluating the susceptibility to liquefaction and earthquake-induced landslides. In this study, we use geostatistical tools in order to compute the spatial correlations of such ground motion parameters. We perform comparisons with other existing models with the aim of: (1) identifying factors that most affect the correlation structure, and (2) quantifying the variability of correlation lengths between different events and regions. Moreover, spatial correlation models are usually calibrated on the within-event component of residuals, obtained based on ergodic ground motion prediction equations (GMPEs). Therefore, we also analyse the spatial correlation of event- and site- corrected residuals, retrieved relaxing the ergodic assumption, to further investigate the factors that determine the spatial dependency of IMs. In order to address these issues, we use the 2016-2017 Central Italy seismic sequence database, which includes nine Mw ≥ 5.0 earthquakes that occurred over a time period of five months. These data allow some uncertainties to be removed and an evaluation of the event-to-event variability of the spatial correlation because the same seismic region is considered. Our preliminary results will provide a more accurate picture of ground motions, and thus improve the modelling of earthquake losses for risk model development

The 3D numerical simulation of near-source ground motion during the Marsica earthquake, central Italy, 100 years later

In this paper we show 3D physics-based numerical simulations of ground motion during one of the most devastating earthquakes in the recent Italian history, occurred on Jan 13, 1915, Marsica, Central Italy. The results provide a realistic estimate of the earthquake ground motion and fit reasonably well both the geodetic measurements of permanent ground settlement, and the observed macroseismic distribution of damage. In addition, these results provide a very useful benchmark to improve the current knowledge of near-source earthquake ground motion, including evaluation of the best distance metrics to describe the spatial variability of the peak values of ground motion, the relative importance of fault normal vs fault parallel components, the conditions under which vertical ground motion may prevail, as well as the adequacy of 1D vs 3D modelling of site amplification effects

Development and Manufacture of the Coil End Spacers of the LHC Pre-series Dipoles

The coil end spacers play an important role in the performance of superconducting coils, as their shape and location determine the mechanical stability of the conductors in the coil ends (and hence the overall coil training performance) and the local field quality. The dipole end spacers are often of a size and a geometry difficult to be industrially series manufactured and measured. Efficiency of the production and related costs are a key issue to achieve the required production rate of the LHC main dipoles at an affordable price. For the latter reasons, a design approach integrating state-of-the-art CAD/CAM optimization techniques allowing to considerably decrease design and machining time was implemented. This paper gives examples and describes the design criteria, the computation methods, the machining and measuring procedures adopted to carry out the pre-series production

Exploring the impact of spatial correlations of earthquake ground motions in the catastrophe modelling process : a case study for Italy

Catastrophe models are important tools to provide proper assessment and financial management of earthquake-related emergencies, which still create the largest protection gap across all perils. Earthquake catastrophe models include three main components, namely: (1) the earthquake hazard model, (2) the exposure model and, (3) the vulnerability model. Simulating spatially distributed ground motion fields within either deterministic or probabilistic seismic hazard assessments poses a major challenge when site-related financial protection products are required. In this framework, we develop ad hoc correlation models for different Italian regions (specifically northern, central and southern Italy) and thereafter we perform both deterministic scenario-based and probabilistic event-based hazard and risk assessments in order to advance the understanding of spatial correlations within the catastrophe modelling process. We employ the OpenQuake engine for our calculations. This is an open-source tool suitable for accounting for the spatial correlation of earthquake ground-motion residuals. Our outcomes, albeit preliminary, demonstrate the importance of considering not only the spatial correlation of ground motions, but also its associated uncertainty in risk analyses. Although loss exceedance probability curves for the return periods of interest for the (re)insurance industry show similar trends, both hazard and risk footprints in terms of average annual losses feature less noisy and more realistic patterns if spatial correlation is taken into account. Such results will have implications for (re)insurance companies evaluating the risk to high-value civil engineering infrastructures

Fling Effects from Near-Source Strong-Motion Records: Insights from the 2016 Mw 6.5 Norcia, Central Italy, Earthquake

open10openD’Amico M., Felicetta C., Schiappapietra E., Pacor F., Gallovic F., Paolucci R., Puglia R., Lanzano G., Sgobba S., Luzi L.D’Amico, M.; Felicetta, C.; Schiappapietra, E.; Pacor, F.; Gallovic, F.; Paolucci, R.; Puglia, R.; Lanzano, G.; Sgobba, S.; Luzi, L

Oral or subcutaneus methotrexate: comparison of the efficacy in inducing sustained disease remission in children with oligoarticular JIA

Introduction: Methotrexate (MTX) is widely adopted as a first line treatment in moderate to severe forms of juvenile idiopathic arthritis (JIA), when NSAIDs and intra-articular corticosteroid injections are not sufficient to control joint disease. MTX is generally prescribed at 10-15 mg/m2 weekly and its administration can be either oral or parenteral (subcutaneous (SC) or intramuscular). Contrasting evidence is available in the literature about the difference in efficacy and safety of MTX, according to the route of administration. Objectives: Aim of the study is to compare the efficacy of oral versus SC MTX in inducing sustained disease remission in children with oligoarticular JIA enrolled in two prospective cohorts. Methods: Children with oligoarthritis included in 3 prospective studies were considered for inclusion: a) the TRIMECA trial (1), b) the MD-Paedigree study (2), c) the PharmaChild registry. Patient evaluated at the IRCCS Istituto Giannina Gaslini and at the Ospedale Pediatrico Bambino Gesù were included if they had received methotrexate treatment as a first line systemic medication within 6 months after disease onset and if a follow up of at least 12 month after treatment initiation was available. Patients were then grouped according to the route of MTX administration. Baseline demographic and disease features were compared between the 2 groups. Efficacy was assessed by comparing the rate of inactive disease (ID) and clinical remission on medication (CRM) at 12 months, the rate of patients changing the route of MTX administration or requiring a biologic medication due to treatment failure. Safety was assessed by comparing the frequency of treatment interruption due to side effects of MTX. Results: 79 patients were included in the study: 43 received oral MTX, 36 received SC MTX. At treatment initiation, disease duration was not different in the two groups; children receiving SC MTX were older at baseline (4.6 yrs vs. 2.5 yrs) and at disease onset (4.2 yrs vs. 2.3 yrs). Disease activity was comparable in the 2 groups, with a median of 2 active joints in both groups. Median MTX dose was 14.4 mg/m2 for oral MTX group and 15.2 mg/m2 for SC MTX (Mann-Whitney U test, p < 0.01). At 12 months, children receiving SC MTX achieved more frequently ID (84.9% vs 43.8%, Chi squared test p < 0.001) and CRM (54.5% vs 28.3%, p = 0.002). Patients in SC MTX group were more often prescribed a biologic medication (22.9% vs 6.5%, p = 0.024), but none of them were switched to the oral administration while 37% of children in oral MTX group were turned to SC MTX. One patient in both groups had MTX treatment suspended due to side effects. Conclusion: Our preliminary results support the evidence of an increased efficacy of MTX in inducing sustained disease remission when it is administered subcutaneously