On the use of ground-motion simulations within ShakeMap methodology: application to the 2008 Iwate-Miyagi Nairiku (Japan) and 1980 Irpinia (Italy) earthquakes

ShakeMap package uses empirical Ground Motion Prediction Equations (GMPEs) to estimate the ground motion where recorded data are not available. Recorded and estimated values are then interpolated in order to produce a shaking map associated with the seismic event of interest. The ShakeMap approach better works in regions with dense stations coverage, where the observed ground motions adequately constrain the interpolation. In poorly instrumented regions, the ground motion estimate mainly relies on the GMPE, that account only for average characteristics of source and wave propagation processes. In this study we investigated the improvement of ShakeMap in the near fault area when including synthetic estimates. We focus on the 2008, Mw 7.0, Iwate-Miyagi Nairiku (Japan) earthquake as a case study because recorded by a huge number of stations. As first we calculated the shakemaps to be used as reference maps and then removed several subsets of stations from the original data-set, replacing them with: (i) the estimations of the ground motion obtained by using a specific GMPE valid for that area, using simple source information such as the earthquake magnitude and fault geometry; (ii) the peak values from synthetic time-histories computed with a hybrid deterministic-stochastic method for extended fault, using the rupture fault model obtained from the kinematic source inversion of strong-motion records. We evaluate the deviations from the reference map and the sensitivity to the number of sites where recordings are not available. Our results show that shakemaps are more and more reliable as the coverage of stations is dense and uniformly distributed in the near-source area. Moreover, the synthetics account for propagation and source properties in a more correct way than GMPE, and largely improve the results. The hybrid maps reach good fitting levels especially when synthetics are used to integrate real data and for particular strong-motion parameters and stations’ distribution

Introduction of seismic source directivity on hazard map

The seismic hazard maps are mainly influenced by the uncertainty associated to the ground motion predictive equation (GMPE). This uncertainty represents the unexplained part of the ground motion and it is mostly related to the choice of the model’s variables. In fact the representation of the ground motion through the GMPEs is simple compared to the complexity of the physical process involved: if only the magnitude and distance are taken into account, GMPEs predicts isoseismals curves that are expected to be isotropic around the hypocenter or along the fault. Instead, the presence of a fault plane across which a process of failure in shear develops makes this general formulation reliable only on average. In fact this failure is responsible of an asymmetry in the seismic radiation known, since Ben-Menhaem (PhD1961), as directivity effect. While the general knowledge of the earthquakes is treated explicitly in the empirical prediction, specific trends like the directivity effects are hidden in the uncertainty sigma. A way to reduce the sigma is therefore to refine the seismic seismic source description inside the GMPEs (e.g. NGA project, Power et al, Earthquake Spectra, 2008). In this framework we propose a strategy to introduce the directivity in the GMPEs and to study its effect on uncertainties and on hazard maps. For this purpose, we have used two different directivity models acting on the GMPE as corrective factors: one proposed by Somerville et al. (Seis.Res.Lett.1997) and the other one proposed by Spudich and Chiou (Earthquake Spectra 2008).The first factor depends on geometrical parameters and comes from theoretical deduction. The second one includes many source parameters and it is a hybrid factor, which functional formulation is deduced from the theory, calibrated on synthetic simulations and scaled on data. The classic hazard equation is then adapted in order to increase the number of source parameters (i.e. adding one integral over the parametric space for each new variable involved) and taking into account the corrective factors for directivity (Spagnuolo, PhD2010). We present the comparisons of hazard maps depending on the directivity factor and on the probability density functions of the fault strike and of the rupture “laterality”

Malignant otitis externa in the antibiotic resistance era: key to successful treatment

Malignant otitis externa in the antibiotic resistance era: key to successful treatment. Objective: Malignant otitis externa (MOE) is a rare aggressive, necrotizing infection of the external auditory canal and the temporal bone. MOE may have a poor prognosis when it is not treated promptly and adequately. It is most commonly reported in males, older individuals, patients with diabetes, or patients that are immunocompromised. Pseudomonas aeruginosa is the main pathogenic agent involved. This study aimed to evaluate a clinical series of patients with MOE and discuss the current literature on the topic. Methodology: This retrospective study included 8 patients with MOE that were evaluated and treated, medically and/ or surgically, at the University Hospital of Ferrara between January 2012 and December 2016. We retrieved data from medical records on the clinical history, imaging, and treatment. Results: In all cases, a microbiological examination disclosed the presence of P. aeruginosa. The infection was eventually controlled in all cases, after a median of 6 months of therapy. All patients were followed-up for an average of 12 months after infection resolution. Conclusion: Currently, no specific guidelines for MOE treatment are available in the literature. Based on our findings, we proposed a diagnostic and therapeutic flow-chart for managing this infection

Approcci deterministici per la stima del moto del suolo: vantaggi e limiti

Nel Progetto DPC-INGV S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”, le stime del moto del suolo sono state ottenute attraverso l’applicazione di diverse tecniche di simulazione di sismogrammi sintetici. Le esperienze maturate nel corso del progetto hanno condotto alla stesura di linee guida per il calcolo degli scenari di scuotimento al bedrock attraverso approcci deterministici. In questo ambito è stata introdotta una classificazione degli scenari deterministici secondo tre diversi livelli di complessità

Role of plasma-induced defects in the generation of 1/f noise in graphene

It has already been reported that 1/f noise in graphene can be dominated by fluctuations of charge carrier mobility. We show here that the increasing damage induced by oxygen plasma on graphene samples result in two trends: at low doses, the magnitude of the 1/f noise increases with the dose; and at high doses, it decreases with the dose. This behaviour is interpreted in the framework of 1/f noise generated by carrier mobility fluctuations where the concentration of mobility fluctuation centers and the mean free path of the carriers are competing factors. Published by AIP Publishing

Variability of kinematic source parameters and its implication on the choice of the design scenario

Near-fault seismic recordings for recent earthquakes (Chi Chi earthquake, 1999, and Parkfield earthquake, 2004) show the high spatial heterogeneity of ground motion. This variability is controlled by fault geometry, rupture complexity, and also by wave propagation and site effects. Nowadays, the number of available records in the near-source region is still not enough to infer a robust parameterization of the ground motion and to retrieve multiparametric predictive equations valid at close distances from the fault. The use of a synthetic approach may help to overcome this limitation and to study the strong ground motion variability. In this article we focus on ground-motion dependence on different earthquakes breaking the same fault, as it has been rarely recorded by instruments. We model seismic scenarios from different rupture models of a fault similar to the 1980 Irpinia, Italy, earthquake source (Mw 6.9). A discrete wavenumber/finite element technique is used to compute fullwave displacement and velocity time series in the low-frequency band (up to 2 Hz). We investigate the variability of the ground motion as a function of different source parameters (rupture velocity, slip distribution, nucleation point, and source time function), whose values depend on the state of knowledge of the physical model driving the process. The probability density functions of the simulated ground-motion parameters, such as displacement response spectrum and peak ground velocity, are used to identify particular scenarios that match specific engineering requests

Modelling directivity effects of the October 21, 2002 (Mw = 5.7), Molise, Southern Italy, earthquake

Acceleration time series recorded by the Italian Strong Motion Network (RAN) during the October 31, 2002 (Mw=5.8), Molise earthquake, are employed in order to investigate source effects on the ground motion in the epicentral area. We consider two different seismogenic sources: a fault model inferred from inversion of teleseismic, regional and local seismic signals [Vallée and Di Luccio, 2005], and a fault model based on seismotectonic data [Basili and Vannoli, 2005]. Both source studies suggest a deep location of the earthquake fault plane (ranging from 6.0 to 20.1 km and from 12.0 to 19.9 km, respectively), however, with considerably different fault lengths (5.2 and 10.5 km, respectively), and widths (14.2 and 8 km, respectively). Due to these differences, only the second model allows for effective horizontal unilateral rupture propagation. Finite fault effects are modelled by the Deterministic-Stochastic-Method (DSM) [Pacor et al., 2005], and the Hybrid Integral-Composite source model (HIC) [Gallovic and Brokesova, 2006]. In both methods k-square slip distributions on the faults are considered. We simulate the October 31, 2002 earthquake considering: 1) Vallée and Di Luccio [2005] faultwith a bilateral rupture propagation, and 2) Basili and Vannoli [2005] fault with unilateral directions of the rupture propagation. The spectral attenuation is modelled using a regional estimate of the quality factor [Castro et al., 2004] and k values estimated from acceleration records. Comparison between synthetic and recorded data at nearby stations (hypocentral distances < 60 km) performed in terms of frequency content and peak ground motion, favours the model with unilateral propagation of the rupture. Assuming the source model with unilateral rupture propagation, we utilize both asymptotic and full wave field methods in order to simulate ground shaking scenarios for an area extending up to 150 km epicentral distance. These results are then subjected to comparison with peak ground accelerations recorded in the far field

Variability of kinematic source parameters and its implication on the choice of the design scenario

Near-fault seismic recordings for recent earthquakes (Chi Chi earthquake, 1999; Parkfield earthquake, 2004) show the high spatial heterogeneity of ground motion. This variability is controlled by fault geometry, rupture complexity, and also by wave propagation and site effects. Nowadays, the number of available records in near-source region is still not enough to infer a robust parameterization of the ground motion and to retrieve multi-parametric predictive equations valid at close distances from the fault. The use of a synthetic approach may help to overcome this limitation and to study the strong ground motion variability. In this paper we focus on ground-motion dependence on different earthquakes breaking the same fault, as it has been rarely recorded by instruments. We model seismic scenarios from different rupture models of a fault similar to the 1980 Irpinia, Italy, earthquake source (Mw 6.9). A discrete wavenumber-finite element technique is used to compute full-wave displacement and velocity time series in the low-frequency band (up to 2 Hz). We investigate the variability of the ground motion as a function of different source parameters (rupture velocity, slip distribution, nucleation point, source time function), whose values depend on the state of knowledge of the physical model driving the process. The probability density functions of the simulated ground motion parameters, such as displacement response spectrum (SD) and peak ground velocity (PGV), have been used to identify particular scenarios that match specific engineering requests