Search results for "seismic"

Centroid-based Cluster Analysis of HVSR Data for Seismic Microzonation

2014

Horizontal to Vertical Spectral Ratio (HVSR) datasets acquired for studies of seismic microzoning in various urban centers of Sicilian towns, have been used to test clustering analysis through a nonhierarchical centroid-based algorithm. In this context clustering techniques may be useful to identify areas with similar seismic behaviour through HVSR data. Centroid-based algorithms generally require the number of clusters, k, and the initial centroid coordinates to be specified in advance. This aspect is considered to be one of the biggest drawbacks of these algorithms. The proposed algorithm doesn’t limit the number of k clusters and choose the initial centroids automatically from the data s…

Seismic Characterization by Inversion of HVSR Data to Improve Geological Modelling

2014

SUMMARY An application of HVSR inversion is presented in order to verify the effectiveness of this technique for purposes of geological reconstruction of the subsoil finalized to studies of seismic microzonation of heavily urbanized areas, where few stratigraphic and geophysical constraints are available and most of the information are derived from the geological maps. In such cases the uncertainty of the results is is enhanced by doubts on the nature of the H/V peaks, not always caused by stratigraphic discontinuities, and to the subjective choices done especially in the step of signal preprocessing. The investigated area (Altavilla Milicia, Sicily) includes the town center and the adjacen…

Seismic investigation for the characterization of a gravity concrete dam

2016

Monitoring of large-scale infrastructures plays an important role for public safety and prevention. The control of the safety assessment of a dam is largely dependent on knowledge of the mechanical parameters of the actual construction, as well as its geological substratum. The application of geophysical methods can considerably contribute to the examination indicating the less consolidated material and the degradation of mechanical parameters. A seismic tomographic approach has been used in a typical gravity concrete dam without reinforcement to detect mechanical properties of the body of the dam and its geological setting. Three seismic travel time tomographies in the dam body as well as …

Parameters affecting the fundamental period of infilled RC frame structures

2015

Despite the fact that the fundamental period appears to be one of the most critical parameters for the seismic design of structures according to the modal superposition method, the so far available in the literature proposals for its estimation are often conflicting with each other making their use uncertain. Furthermore, the majority of these proposals do not take into account the presence of infills walls into the structure despite the fact that infill walls increase the stiffness and mass of structure leading to significant changes in the fundamental period numerical value. Toward this end, this paper presents a detailed and in-depth analytical investigation on the parameters that affect…

Fluid-triggered earthquake swarms in the Rwenzori region, East African Rift—Evidence for rift initiation

2012

The Rwenzori Mountains are located within the Albertine Rift Valley in western Uganda. To monitor the microseismic activity in the area we have deployed a seismic network of up to 35 stations for a period of about 20 months. The analysis of the recordings revealed several earthquake clusters within a restricted area NE of the mountain block. The clusters form elongated pipes with 1–2 km diameter and vertical extensions of 3–5 km. Most of them are located in 5–16 km depths; however one cluster reaches down to 22 km. Each cluster is composed of a series of single earthquake swarms with durations between a few days and more than a week, interrupted by intervals of inactivity of up to several m…

RESILIENCE AND VULNERABILITY OF URBAN SYSTEMS. A METHODOLOGICAL PROPOSAL FOR SEISMIC RISK MITIGATION

2014

Resilience in small urban centers with a strong historical connotation

2015

La resilienza della città storica, misurata dagli eventi rispetto a calamità naturali e fenomeni emergenziali, si presenta spesso al di sopra di qualunque aspettativa. Soprattutto quando principio insediativo, trasformazioni consequenziali a calamità e ridondanze hanno di fatto aumentato la coping capacity e la capacity of response del costruito storico rendendole elevate e di significato. Nonostante ciò la necessità di implementazione di nuove qualità, nell’ottica di riappropriazione dei patrimoni urbani disseminati nel territorio e spesso abbandonati o poco popolati, pone il bisogno di retrofit, manutenzione e misure gestionali che incrementino sicurezza e resilienza. Potendosi indubbiame…

Deep-rooted “thick skinned” model for the High Atlas Mountains (Morocco). Implications for the structural inheritance of the southern Tethys passive …

2006

A re-interpretation of the deep structure of the High Atlas is presented through integration of geophysical and geological data, highlighting the architectural significance of the southern Tethys palaeomargin. Previous crustal models suggest the occurrence of a flat intra-crustal detachment at a depth of � 20 km, a zone where surface thrusts merge and below which the lower High Atlas crust appears continuous. However, within this study seismic refraction data, electrical resistivity surveys and gravity modelling all appear to detect a jump in crustal thickness between the High Atlas and the northern plains. We interpret these data as penetration by thrusts within the ‘‘South-Atlasic fault’’…

Experimental determination of viscous damper parameters in low velocity ranges

2017

In the last decades many strategies for seismic vulnerability mitigation of structures have been developed through analytical studies and experimental tests. Among these, energy dissipation by external devices assumes a great relevance for the relative design simplicity, even if applied to complex structures, and the effectiveness in reducing seismic demand. In particular, the use of fluid viscous dampers represents a very attractive solution because of their velocity-dependent behaviour and relatively low costs. The application on structures requires specific study under seismic excitation and a particular care of structural details. In this context the use of proper constitutive models fo…

Seismic analysis and risk mitigation of existing constructions

2016

Following a thorough and lengthy procedure, we would like to thank all contributors for their highest calibre papers, which comprise the Special Issue on “Seismic analysis and risk mitigation of existing constructions” of the Open Construction and Building Technology Journal. The topic of the Special Issue encompasses a large number of issues spanning the design of special interventions for the reduction of the effects of earthquakes on civil structures and infrastructures, to the structural identification and assessment issues. The field of seismic engineering is continuously looking for new strategies and methods, which empower the designers and make them able to obtain more accurate resp…