Analisi della risposta sismica di un edificio campione nel Comune di Ariano Irpino (AV)

Nella pratica ingegneristica vengono usate correlazioni derivate da regressioni statistiche tra numero dei piani degli edifici e frequenze di risonanza. Tuttavia la discrepanza tra comportamento reale e valori aspettati può essere talvolta significativa, e solo l’acquisizione di dati sperimentali consente di comprendere il reale comportamento dinamico di una struttura. La sperimentazione, in situazioni anche complesse, e la raccolta di nuovi dati possono essere molto importanti nel campo dell’ingegneria strutturale. In questo articolo vengono presentati i risultati del monitoraggio sismico effettuato su un edificio campione in muratura (il municipio di Ariano Irpino), tipologia costruttiva largamente diffusa tra gli edifici pubblici strategici (ad esempio scuole, caserme ed ospedali). Sono state utilizzate 7 stazioni sismologiche a sei canali equipaggiate con sismometri ed accelerometri. I dati sismici sono stati acquisiti in modalità continua, in punti strategici della struttura, su diversi livelli, dal gennaio 2006 a dicembre 2007. Sono stati selezionati una ventina di terremoti di magnitudo bassa o intermedia (1.5 ≤ M ≤ 4.8) avvenuti a distanze epicentrali variabili da 4 a 116 km. Le registrazioni sono state analizzate sia mediante la tecnica dei rapporti spettrali rispetto alla base dell’edificio sia calcolando i rapporti spettrali tra componente orizzontale e verticale di ogni sensore. L’analisi svolta ha consentito di evidenziare numerose frequenze di vibrazione dell’edificio. Mediante simulazioni numeriche su un modello tridimensionale rappresentativo della struttura in esame è stato possibile associare i picchi in frequenza ai modi propri in campo lineare. In particolare, sono stati ben identificati i primi 3 modi di vibrazione (due flessionali ed uno rotazionale)

FORTI EFFETTI DI AMPLIFICAZIONE DEL MOTO IN ZONA DI FAGLIA DURANTE LA SEQUENZA SISMICA DEL 2009 IN ABRUZZO

Negli anni 1997-1998, durante la sequenza dell’Umbria-Marche, la stazione accelerometrica di Nocera Umbra superò ripetutamente, per terremoti di magnitudo > 5, il picco di accelerazione di 0.5 g. Tali valori furono i maggiori mai registrati in Italia, e apparvero subito inusuali per terremoti di faglia normale a magnitudo moderate. Una serie di studi del sito della stazione permise di attribuire l’ampiezza anomala a un forte effetto di amplificazione locale prodotto dalle variazioni verticali della velocità delle onde di taglio nella roccia danneggiata di una faglia sub-verticale in prossimità della stazione. Anche durante i terremoti della sequenza Aquilana si sono trovate evidenze di effetti analoghi. La stazione a banda larga FAGN, in prossimità della faglia di San Demetrio, ha mostrato una accentuata variabilità dell’ampiezza delle sue registrazioni, con valori che superano fino ad un fattore 10 le ampiezze delle stazioni vicine. Mediante un’analisi su 350 terremoti si è trovato che le massime amplificazioni avvengono per terremoti localizzati a sud-ovest della stazione, in posizione favorevole alla propagazione nella zona di faglia dalla sorgente al ricevitore. Utilizzando metodi sia analitici che numerici è stato possibile attribuire gli effetti osservati alle eterogeneità di una zona di faglia larga 300-400 m e profonda 3 km, approssimativamente, con una riduzione di velocità di circa il 30% rispetto alla roccia non deformata. Anche il forte impulso di spostamento di 40 cm picco-picco registrato durante la scossa principale a Castello d’Ocre da una stazione GPS (CADO) con campionamento a 10 Hz non trova giustificazione plausibile se non modellando un effetto di risonanza in prossimità dello strumento. In questo caso è possibile generare modelli che riproducano l’osservazione usando valori della larghezza della zona di faglia di qualche centinaio di metri con forti riduzioni della velocità delle onde di taglio rispetto ai blocchi rigidi adiacenti. Queste osservazioni confermano la potenziale pericolosità del territorio in prossimità delle zone di faglia, nonostante non siano emerse durante il terremoto dell’Aquila chiare evidenze di anomalie del danno persistenti lungo le faglie. Recenti studi in California sembrano mettere in luce l’estrema variabilità delle onde intrappolate nelle zone di faglia, per cui l’effetto appare sporadicamente sia per quanto riguarda le stazioni di registrazione lungo la faglia che per quanto riguarda le zone-sorgenti nella faglia capaci di generare onde intrappolate.PublishedPrato3.1. Fisica dei terremotiope

Seismic site response estimation in the near source region of the 2009 L'Aquila, Italy, Earthquake

To better estimate the seismic ground motion during the April 6th, 2009 earthquake in L'Aquila, we deployed temporary arrays in the near-source region. Several arrays have been successively set up in the Aterno valley's epicentral area and have recorded the aftershocks that followed the main shock, between April and September. The data has been processed in order to study the spectral ratios of the horizontal component of ground motion at the soil site and at a reference site, as well as the spectral ratio of the horizontal and the vertical movement at a single recording site. The results obtained confirm the presence of large amplification effects in both L'Aquila's historic centre and in the suburban areas. The resonance frequency has been found to be close to 0.6 Hz in downtown L'Aquila whereas the suburban areas show amplification at frequencies ranging from 2 Hz to 5 Hz.PublishedSkopje, Macedonia4.1. Metodologie sismologiche per l'ingegneria sismicaope

Seismic site response estimation in the near source region of the 2009 L'Aquila, Italy, Earthquake

To better estimate the seismic ground motion during the April 6th, 2009 earthquake in L'Aquila, we deployed temporary arrays in the near-source region. Several arrays have been successively set up in the Aterno valley's epicentral area and have recorded the aftershocks that followed the main shock, between April and September. The data has been processed in order to study the spectral ratios of the horizontal component of ground motion at the soil site and at a reference site, as well as the spectral ratio of the horizontal and the vertical movement at a single recording site. The results obtained confirm the presence of large amplification effects in both L'Aquila's historic centre and in the suburban areas. The resonance frequency has been found to be close to 0.6 Hz in downtown L'Aquila whereas the suburban areas show amplification at frequencies ranging from 2 Hz to 5 Hz

The contribution of seismic data in microzonation studiesfor downtown L’Aquila

After the 2009 April 6th Mw 6.3 L’Aquila earthquake (Central Italy) the Italian Civil Defense Department promoted the microzoning study in the ten zones in the epicentral area that suffered major damage. In this paper we present the activities and the results concerning a temporary seismic network installed in the historical L’Aquila city center indicated as “macroarea 1” in the microzoning project. Seismic data were collected to investigate the amplification effects in the city and to support the microzoning activities in verifying both geological profiles and 1D numerical modeling of the seismic response of the city. The conventional spectral approaches using both microtremor and earthquake data allowed to determine the fundamental resonance frequencies and the amplification factors within the city respectively. The spatial variability of these quantities can be related to the geological and geomorphologic characteristics of the investigated area. A comparison between the network data and the data recorded by the two strong motion instruments installed in the city was also made. This allows verifying the relative response of the accelerometric stations that recorded in the city the major events of the sequence.Published741–7594.1. Metodologie sismologiche per l'ingegneria sismicaJCR Journalreserve

Preliminary results from EMERSITO, the rapid response network for site effect studies

On May 20, 2012, at 02:03 UTC, a ML 5.9 reverse-fault earthquake occurred in the Emilia-Romagna region, northern Italy, at a hypocentral depth of 6.3 km (http://iside.rm. ingv.it/), close to the cities of Modena and Ferrara in the plain of the Po River. The epicenter was near the village of Finale Emilia where macroseismic intensity was assessed at 7 EMS98 [Tertulliani et al. 2012, this issue], while the closest accelerometric station, MRN, located less than 20 km west-ward at Mirandola (Figure 1) recorded peaks of ground accelerations of about 300 cm/s2 (www.protezionecivile.gov.it/resources/ cms/documents/Report_DPC_1_Emilia_EQSd.pdf ). The mainshock triggered liquefaction phenomena a few kilometers eastwards of the epicenter, around the village of San Carlo. On the same day, two other shocks of ML 5.1 followed (02:07, 13:18 GMT; http://iside.rm.ingv.it/). On May 29, 2012, at 07:00 UTC another ML 5.8 earthquake hit the region (http://iside.rm.ingv.it/), with the epicenter close to the village of Mirandola (Figure 1). Three other strong aftershocks occurred afterwards, of ML 5.3 (May 29, at 10:55), ML 5.2 (May 29, at 11:00) and ML 5.1 ( June 3, at 19:20). For a detailed description of the seismic sequence, see Moretti et al. [2012], Scognamiglio et al. [2012], and Massa et al. [2012], in this issue. The Emilia seismic sequence resulted in 25 casualties, several of whom were among the workers in the many factories that collapsed during working hours, and there was extensive damage to monuments, public buildings, industrial sites, and private homes. The Po Plain region that was struck by the 2012 Emilia seismic sequence is a very large E-W trending syntectonic alluvial basin, which covers about 45,000 km2. It is surrounded by the Alps to the north and the Apennines to the south, and it is filled with Plio-Pleistocene terrigenous sediments and Holocene deposits, with depths varying from a few hundred meters up to several kilometers. The epicentral area was located south of the Po River, corresponding to the active front of the northern Apennines thrust belt (north-vergence), which is composed of buried folds and thrust faults that locally produce structural highs (Figure 1), and are known as Pieghe Emiliane and Ferraresi [Pieri and Groppi 1981]. The top of this limestone and marl bedrock rises to ca. 100 m from the surface and has been derived locally from borehole logs. The seismic response of this ca. 150-m-deep soft cover was investigated using weak-motion events and microtremors recorded in a borehole by Margheriti et al. [2000]. The occurrence of the May 2012 seismic sequence made it possible to study the seismic response under near-field conditions. These studies are aimed at providing tools to reduce the impact of future earthquakes on the local communities. In addition to the amplification due to one-dimensional (1D) resonance, it is well known that seismic responses of deep sedimentary basins are affected by 2D and 3D effects (e.g., wave diffraction, conversion at the basin edges, trapping and focusing of energy within the soil volume). Evidence of basin-induced surface waves and edge effects have been observed in many basins worldwide; e.g., the Osaka basin in Japan [e.g., Kawase 1996, Pitarka et al. 1998], various southern California basins [Graves et al. 1998, Day et al. 2008], and the Parkway basin in New Zealand [Chávez-García et al. 1999]. In Italy, good examples of site amplification in alluvial basins can be found for the Gubbio, Città di Castello, L'Aquila and Fucino basins [ Bordoni et al. 2003, Bindi et al. 2009, Cara et al. 2011, Milana et al. 2011]. Therefore, the day after the mainshock, the INGV rapidresponse network for site effects, called EMERSITO, planned the experiments presented in this report. EMERSITO put together independent research groups from several territorial centers of the Istituto Nazionale di Geofisica e Vulcanologia (INGV; National Institute of Geophysics and Volcanology) who agree to collaborate spontaneously and on the basis of a data archiving and sharing policy. They then deployed their seismic equipment in the epicentral area, building on the experience of the 2009 L'Aquila earthquake [Di Giulio et al. 2011, Margheriti et al. 2011, Milana et al. 2011]. The deployment was planned also in collaboration with the geological survey of the Regione Emilia Romagna (Servizio Geologico e Sismico e dei Suoli) and the University of Modena, as well as being in the framework of SISMIKO [Moretti et al. 2012]. As a result of this effort, since May 22, three linear arrays have been deployed (Figure 1), with a total of 22 sites instrumented, 16 of them equipped with both velocimeters and accelerometers. These arrays recorded most of the aftershock sequence, including the MW 5.8 May 29, 2012, 07:00 earthquake. The continuous recordings will be archived into the EIDA database (http://eida.rm.ingv.it/) under restricted access. The aim of this report is to describe the experiments performed by the EMERSITO team, as well as the main features of the recorded earthquakes. A preliminary insight in the site response of the investigated area within the context of the geological structure of the Po Plain is also given

NERA project - Deliverable D11.4: Array measurements

The aim of this Task is to present the seismological data and some preliminary empirical results related to two deployed specific arrays; (a) the Argostoli seismological array and (b) the Fucino seismological array. Both experiment arrays provided high quality data that along with corresponding geological and geophysical measurements may serve to critical evaluation of site effects and basin effects. In addition, work on modelling of basin effects may be significantly benefited by the observed acquired in both sites. Given that the analyses of the data obtained during the aforementioned experimental arrays will be performed in close link with activity of NERA-JRA3, the following goals are set: To investigate the link between ground motion spatial variability, strains, seismic wavefield and subsurface properties To compare numerical estimates of ground strain with actual measurements To investigate the capability of estimating ground strains from noise correlation studies. In order to organize and accomplish the work according to the initial schedule, several meetings (actual or/and Skype) among the participants took place during the 2nd year of the NERA-JRA1 project. Minutes of these meetings are given in Appendices 1, 2, 3 and 4.Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation Project, Seventh Framework Programme EC project number: 262330Published4T. Sismologia, geofisica e geologia per l'ingegneria sismic

The 2016–2017 earthquake sequence in Central Italy: macroseismic survey and damage scenario through the EMS-98 intensity assessment

In this paper we describe the macroseismic effects produced by the long and destructive seismic sequence that hit Central Italy from 24 August 2016 to January 2017. Starting from the procedure adopted in the complex field survey, we discuss the characteristics of the building stock and its classification in terms of EMS-98 as well as the issues associated with the intensity assessment due to the evolution of damage caused by multiple shocks. As a result, macroseismic intensity for about 300 localities has been determined; however, most of the intensities assessed for the earthquakes following the first strong shock on 24 August 2016, represent the cumulative effect of damage during the sequence. The earthquake parameters computed from the macroseismic datasets are compared with the instrumental determinations in order to highlight critical issues related to the assessment of macroseismic parameters of strong earthquakes during a seismic sequence. The results also provide indications on how location and magnitude computation can be strongly biased when dealing with historical seismic sequences.Presidenza del Consiglio dei Ministri - Dipartimento della Protezione Civile (DPC)Published2407–24314T. Sismicità dell'Italia1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami2SR TERREMOTI - Gestione delle emergenze sismiche e da maremoto5SR TERREMOTI - Convenzioni derivanti dall'Accordo Quadro decennale INGV-DPCJCR Journa

The impact of weapons and unusual objects on the construction of facial composites

The presence of a weapon in the perpetration of a crime can impede an observer’s ability to describe and/or recognise the person responsible. In the current experiment, we explore whether weapons when present at encoding of a target identity interfere with the construction of a facial composite. Participants encoded an unfamiliar target face seen either on its own or paired with a knife. Encoding duration (10 or 30 s) was also manipulated. The following day, participants recalled the face and constructed a composite of it using a holistic system (EvoFIT). Correct naming of the participants’ composites was found to reduce reliably when target faces were paired with the weapon at 10 s but not at 30 s. These data suggest that the presence of a weapon reduces the effectiveness of facial composites following a short encoding duration. Implications for theory and police practice are discussed

Evaluation of the local site effects in the upper and middle Aterno valley

In the months following the April 6th, 2009, L’Aquila earthquake, several Italian and foreign research institutions installed dozens of seismic stations to monitor more than 100 localities with the aim of studying the local site effects in the epicentral area (upper and middle Aterno valley). The stations (accelerometers and velocimeters) have been deployed inside or very close to the inhabited areas. Among the investigated sites there are Onna, where almost the totality of the buildings collapsed, and the historic centre of L’Aquila, both towns suffering many casualties. The preliminary results for the examined sites show an extreme variability of ground motion and significant amplification for the most damaged localities.In press4.1. Metodologie sismologiche per l'ingegneria sismicaN/A or not JCRope