Fragility curves and seismic demand hazard analysis of rocking walls restrained with elasto-plastic ties

AbstractThe dynamic stability of out‐of‐plane masonry walls can be assessed through non‐linear dynamic analysis (rocking analysis), accounting for transverse walls, horizontal diaphragms and tie‐rods. Steel tie‐rods are widely spread in historical constructions to prevent dangerous overturning mechanisms and can be simulated by proper elasto‐plastic models. Conventionally, design guidelines suggest intensity‐based assessment methods, where the seismic demand distribution directly depends upon the selected intensity measure level. Fragility analysis could also be employed as a more advanced procedure able to assess the seismic vulnerability in a probabilistic manner. The boundedness of this approach is herein overcome by applying a robust stochastic seismic performance assessment to obtain seismic demand hazard curves. A sensitivity study is carried out to account for the influence of wall geometry, the minimum number of seismic inputs, and the mechanical parameters of tie‐rods. Fragility analysis, prior to seismic demand hazard analysis is applied on over 6000 analyses, revealing that intensity measures are poorly correlated both for 1‐D and 2‐D correlation, hardly leading to the selection of the optimal intensity measure. The tie‐rod ductility, followed by its axial strength and wall size, is the mechanical parameter mostly influencing the results, whereas the wall slenderness does not play a significant role in the probabilistic response

Impact Factor, Citation Index, H-Index: are researchers still free to choose where and how to publish their results?

Over the last decade, the demand to evaluate the impact of any given research study, the credentials of a researcher, and the influence that any single research unit or agency has on the world of research has constantly grown. Many tools have been developed and applied to evaluate the level of innovation, originality and continuity of a single researcher in an objective way. As a consequence, there are comparisons of the performances of different research agencies. Some of these tools, which often provide the result as an ‘index’, are briefly described in this study. However, it is clearly evident that the evaluations provided by these instruments do not always correspond to the real impact of the research, nor are they unique. Indeed, the same index computed using similar criteria on different databases gives different scores, which can lead to confusion and contradictions. In this contribution, the principal anomalies, problems and failures of these evaluation schemes are described. The most evident of these arise from the nature of the evaluation, which being automated, cannot establish the role of any single researcher in papers of ‘pooled’ research, and cannot recognize similar or duplicated papers by the same researcher(s) in more than one journal. The ‘selecting’ effects that these evaluation indices can have on the research are then discussed. Indeed, in an attempt to obtain the highest possible scores in terms of citations, there is a tendency of the single scholar to avoid studies that deal with small areas, or with scientific problems that do not have a broad interest or provide applicative results. In all of these cases, an article describing such studies will in all likelihood appear in a ‘minor journal’ (one with a low impact factor). As a consequence, this will provide a low citation index, will not significantly contribute to the authors’ H-index, and/or will only be published as a report. Moreover, a discussion on the role that these evaluation indices can have in the world of research is presented. Particular attention is paid to the consequences in the field of the geoethics, where scientific, technological, methodological and socio-cultural aspects need to be considered in a different order to that expected in a pure meritocracy

Implicazioni sismotettoniche del terremoto di Taggia del 26 Maggio 1831

Il 26 Maggio 1831, alle ore 10.30, la Liguria occidentale fu interessata da un terremoto che colpì in modo distruttivo 15 paesi ed interessò anche la provincia di Genova, il Piemonte e la Provenza. L’area dei massimi effetti fu localizzata nella parte prossima al mare della valle Argentina, in particolare nei territori dei comuni di Castellaro, Taggia e Bussana, che furono i centri maggiormente danneggiati. In particolare, a Bussana furono distrutte 24 case e 49 vennero demolite poiché pericolanti. A seconda del catalogo considerato, le informazioni macrosismiche disponibili per questo evento sono relative a circa 30 località. Nonostante questo numero non sia in assoluto esiguo, tuttavia appare sottostimato rispetto a quello di altri eventi di caratteristiche simili e periodi contigui, come ad esempio quello del 1854 (86 osservazioni), quello del 1818 (46 siti). Stante l’impossibilità di aumentare il numero di dati a disposizione, e potendo utilizzare solo quelli pubblicati, sono state comunque effettuate una revisione della localizzazione ed un calcolo preliminare delle caratteristiche della sorgente utilizzando il programma Boxer 3.3. I risultati ottenuti conducono alla interpretazione secondo cui l’azimuth della sorgente sismogenetica sarebbe in direzione quasi perpendicolare a quella della faglia Saorge-Taggia

Research and press: an (im)possible relationship?

The relationship between research results and press communications is very tangled, does not matter which study field one considers. In fact similar complications affect medicine, earth sciences, biology, natural sciences. This abstract concerns the earth sciences due to the frequent natural disasters that strike our planet and thus to the interest of the press towards these phenomena than other scientific aspects, for example, of biology or zoology. However similar consideration could probably apply to many other scientitic topics and environments. Although results proposed by both scientists and journalists aim to inform people, they have completely different rhythms, language and operative means. The coexistence of the two sources and flows of information is certainly difficult already in everyday life but becomes almost critical right after the occurrence of a natural catastrophe. In summary, the main differences in the way the same information is treated by the two parties are: - the scientific result is always accompanied by the uncertainties with which it has been obtained. When interpreted by a journalist, the part of the information concerning the likely associated errors is neglected for several reasons. It is difficult to understand and especially to explain to the reader; does not match the requirement for modern news to be short and fast; apparently does not change the principal information. - the scientific result is always susceptible of adjustments and changes. It is often very hard to know when a result is definitive in science since other data or other evidences may slightly or significantly change the conclusions. This aspect does not match the requirements for press news, that cannot be published as “preliminary” - as a consequence, the scientific result needs time. The reasons are already summarized above: new data may be incoming, new comments or studies from colleagues working in similar fields may be available, the availability of more modern or powerful instruments may change the point of view. Again, this is incompatible with the press necessities: the information must be available as soon as possible, does not matter if it is preliminary or not precise. The concept of "good" in press often coincides with "prompt". - the scientific results need technical language, which is indeed to be avoided in a newspaper article or a tv talk. Therefore the problem of how to render scientific concepts understandable becomes crucial. As a conclusion, a compromise between the two groups of necessities is required. It is clear that important steps have been done from both sides in the last years: researcher are now trying to disseminate their results to a broader audience while journalists try to adopt a more technical language educating readers or spectators to enlarge their dictionary. But unfortunately it is not enough, as some examples of the presentation will show

The role of instrumental versus macroseismic locations for earthquakes of the last century: a discussion based on the seismicity of the North-Western Apennines (Italy)

Many seismological observatories began to record and store seismic events in the early years of the twentieth century, contributing to the compilation of very valued databases of both phase pickings and waveforms. However, despite the availability of the instrumental data for some of the events of the last century, an instrumental location for these earthquakes is not always computed; moreover, when available, the macroseismic location is strongly preferred even if the number of points that have been used for it is low or the spatial distribution of the observations is not optimal or homogeneous. In this work I show how I computed an instrumental location for 19 events which occurred in the Garfagnana-Lunigiana region (Northern Tuscany, Italy) beginning from 1902. The location routine is based on a Joint Hypocentral Determination in which, starting from a group of master events, the systematic errors that may affect the data are summed up in the corrective factors complementing the velocity propagation model. All non-systematic errors are carefully checked and possibly discarded by going back to the original data, if necessary. The location is then performed using the classic approach of the inverse problem and solved iteratively. The obtained locations are then compared to those already available from other macroseismic studies with the aim to check the role to be attributed to the instrumental locations. The study shows that in most cases the locations match, in particular when considering the different significance of the location parameters, especially for the strongest events: the instrumental location provides the point where the rupture begins, while the macroseismic one is an estimate of the area where the earthquake possibly took place. This paper is not meant to discuss the importance and the necessity of macroseismic data; instead, the aim is to show that instrumental data can be used to obtain locations even for older seismic events, without any intention to define which location is better or more reliable

Variations of stress directions in the western Alpine arc

The western Alpine arc originated during the Cretaceous orogenesis as a consequence of the continental collision between the European and Adriatic plates. The distribution of forces acting in this sector of the Alps is still somewhat uncertain. In the past, some efforts have been made to map the distribution of P and T axes but it is known that these can be substantially different from the principal stress directions. In recent work, we presented a first attempt to determine the directions of σ1 and σ3, which we could compute only for a ‘local' regime at the level of the magnitude of the larger events that occurred in the area. To obtain the stress orientation, we applied the technique developed by Gephart and Forsyth to invert fault plane solutions. In this work we present the results of a detailed analysis performed on a larger area, applying the same methodology. A total of 86 earthquakes with magnitudes ranging from 2.5 to 5.3 has been used for inversion. The results confirm the impossibility of defining, within the available data, a regional stress field. In fact, different local behaviours have been demonstrated in four subregions. For the first subregion, namely the northern part of the western Alps, the inversion of 28 earthquakes, resulting in a misfit of 5.9°, revealed a distensive regime orientated N-S. For the second subregion, the outer part of the western Alps, the inversion of 16 earthquakes led to a misfit of 5.3° for a distensive E-W orientated regime. In the inner part of the chain, an opposite result was obtained by the inversion of 14 earthquakes, confirmed by a misfit of 4.7°. Finally, the region of the Ligurian Sea revealed an almost horizontal NW-SE orientated σ1, whereas σ3 is NE-SW orientated with a dip of around 30°-40°. The inversion for this subarea was carried out on a data set of 28 earthquakes and characterized by a misfit of 7.1°. The uncertainty of the stress axis orientation (90 per cent confidence limits) is, on average for all inversions, around 40

Il terremoto a scuola: una occasione di legame tra società e ricerca

In una società come quella attuale, in cui sapere e tematiche sociali e ambientali si fondono nella realtà di tutti i giorni, la scuola non svolge più la sola semplice funzione di insegnamento. Essa ha infatti il ben più difficile compito di rendere i giovani consapevoli della realtà in cui vivono e di guidarli verso la conoscenza di tutto ciò che possa essere utile a migliorare e preservare ciò che li circonda. Questo vale in ogni ambito e si applica indifferentemente all’ambiente, alla cultura umanistica, al patrimonio culturale, a quello economico. In questo compito gli insegnanti possono essere agevolati dalla collaborazione con i ricercatori che, per loro funzione, tentano di risolvere problemi che incidono sul patrimonio e possono contribuire alla cultura della scuola in campi specifici ma soprattutto negli aspetti applicativi e con gli aggiornamenti a cui spesso, con i loro studi, contribuiscono in prima persona. In questo senso e con questo obiettivo l’Istituto Nazionale di Geofisica e Vulcanologia (INGV nel seguito) ha da molti anni intrapreso un lungo cammino fatto di reciproche collaborazioni con insegnanti e scuole, istituendo un apposito gruppo di lavoro specializzato in divulgazione per le scuole e per i cittadini. Negli anni è stato creato un sostanzioso patrimonio di pubblicazioni a stampa, supporti multimediali, audiovisivi e siti web creati con il compito di agevolare la divulgazione su temi scientifici

DISSEMINATING SEISMOLOGY IN LIGURIA, NORTHERN ITALY

We describe and discuss some activities of our working group to disseminate scientific issues concerning seismology to the students of the Region Liguria

T waves in Western Mediterranean Sea after the May 21, 2003 Algerian earthquake

Aim of this paper is to discuss on the T phases generated after the mb 6.5 earthquake that shook Algeria on May 21, 2003. The seismograms, recorded by a cluster of seismic stations located on the coast facing the Ligurian Sea, Northern Italy, some 800 km N-NE from the source, represent a good database able to shed some light on the recognition, propagation and characteristics of these quite uncommon phases. The occurrence and the recording of T phases are in fact due to particular conditions, and require both particular characteristics of the bathymetric slope and the existence of a clear path between the instruments and the earthquake’s source: these constraints are exactly realized in the north-western part of the Mediterranean Sea, whose coasts have been affected several times in the past by similar events. The preliminary investigations on the complex recorded seismogram show two different behaviours for stations close the coast and inland. In both cases, two distinct T phases (namely T1 and T2) are observed. In one case they have apparent velocities close to an average SOFAR channel, and are thus the recording of direct T phases. In particular, T1 is probably a precursor due to some scattering, while T2 is the direct T wave. Conversely, the recordings of the stations inland show apparent velocities that suggest back conversion of the original T to P and S waves and a crustal path. The frequency content of the T phases, as derived from the spectral analysis, reveals marked amplitude peaks also in the range 1-3 Hz, conversely to what was proposed by other authors for similar occurrences in other parts of the world. Since the geometry and shape of the SOFAR channel vary, it is highly likely that the spectrum is biased by the water conditions and the frequency content might change in different seas. Finally, the attenuation of the T phase does not depend on the actual distance of the receiver from the source but rather from the backconversion point: the amplitude varies thus with the in-land path and decreases proportionally to x−1