Georisks in the Mediterranean and their mitigation

An international scientific conference organised by the Seismic Monitoring and Research Unit, Department of Geoscience, Faculty of Science, Department of Civil and Structural Engineering and Department of Construction and Property Management, Faculty of the Built Environment, University of Malta.Part of the SIMIT project: Integrated civil protection system for the Italo-Maltese cross-border area. Italia-Malta Programme – Cohesion Policy 2007-2013This conference is one of the activities organised within the SIMIT strategic project (Integrated Cross-Border Italo-Maltese System of Civil Protection), Italia-Malta Operational Programme 2007 – 2013. SIMIT aims to establish a system of collaboration in Civil Protection procedures and data management between Sicilian and Maltese partners, so as to guarantee the safety and protection of the citizens and infrastructure of the cross-border area. It is led by the Department of Civil Protection of the Sicilian region, and has as other partners the Department of Civil Protection of Malta and the Universities of Palermo, Catania and Malta. SIMIT was launched in March 2013, and will come to a close in October 2015. Ever since the initial formulation of the project, it has been recognised that a state of national preparedness and correct strategies in the face of natural hazards cannot be truly effective without a sound scientific knowledge of the hazards and related risks. The University of Malta, together with colleagues from other Universities in the project, has been contributing mostly to the gathering and application of scientific knowledge, both in earthquake hazard as well as in building vulnerability. The issue of seismic hazard in the cross-border region has been identified as deserving foremost importance. South-East Sicily in particular has suffered on more than one occasion the effects of large devastating earthquakes. Malta, although fortunately more removed from the sources of such large earthquakes, has not been completely spared of their damaging effects. The drastic increase in the building density over recent decades has raised the level of awareness and concern of citizens and authorities about our vulnerability. These considerations have spurred scientists from the cross-border region to work together towards a deeper understanding of the underlying causes and nature of seismic and associated hazards, such as landslide and tsunami. The SIMIT project has provided us with the means of improving earthquake surveillance and analysis in the Sicily Channel and further afield in the Mediterranean, as well as with facilities to study the behaviour of our rocks and buildings during earthquake shaking. The role of the civil engineering community in this endeavour cannot be overstated, and this is reflected in the incorporation, from the beginning, of the civil engineering component in the SIMIT project. Constructing safer buildings is now accepted to be the major option towards human loss mitigation during strong earthquakes, and this project has provided us with a welcome opportunity for interaction between the two disciplines. Finally the role of the Civil Protection authorities must occupy a central position, as we recognize the importance of their prevention, coordination and intervention efforts, aided by the input of the scientific community. This conference brings together a diversity of geoscientists and engineers whose collaboration is the only way forward to tackling issues and strategies for risk mitigation. Moreover we welcome the contribution of participants from farther afield than the Central Mediterranean, so that their varied experience may enhance our efforts. We are proud to host the conference in the historic city of Valletta, in the heart of the Mediterranean, which also serves as a constant reminder of the responsibility of all regions to protect and conserve our collective heritage.peer-reviewe

Update on the Malta Seismic Network

The Central Mediterranean is one of the most seismically active and tectonically dynamic regions in the Mediterranean characterised by a system of extension in the north (Appenines), a slab rollback in the centre (Calabria) and a rift zone in the south (Sicily Channel), all within a general convergent setting between the African and European plates. Unlike the northern regions of the Central Mediterranean (and others such as along the Hellenic subduction zone), earthquake monitoring within the Sicily Channel has, so far, been inadequate. During the last two years the Seismic Monitoring and Research Unit (University of Malta) has been upgrading its earthquake monitoring capabilities, with the addition of new broadband seismic stations and state-of-the-art real-time monitoring. The new setup will not only help to investigate better the regional seismicity within the Sicily Channel, but will also facilitate early warning of potentially felt earthquakes originating hundreds of kilometres away from Malta. This investment is part of the project SIMIT (B1-2.19/11) funded by the Italia-Malta Operational Programme 2007–2013.peer-reviewe

Site characterisation and response study in Rabat, Malta

The investigation of local ground conditions is an important part of seismic hazard assessment (Fäh et al., 2003). Local geology can greatly alter the seismic waves from earthquakes by amplifying their amplitude, changing the frequency content and increasing the shaking duration during an earthquake (Kramer, 1996). Sedimentary structures hosting dense settlements are likely to suffer from heavy damage, even though they can be situated away from the epicentre of the earthquake (Zor et al., 2010). The main parameters responsible for such effects are the shear-wave velocity (VS) structure and thickness of the sedimentary cover, the impedance contrast between the soft sediments and the underlying bedrock as well as the geometry of their interface (Parolai et al., 2006). Site response studies contribute to earthquake-hazard mitigation strategies such as seismic risk assessments, emergency response-preparedness and land use planning by considering existing and proposed buildings (Zor et al., 2010). Since 1530, an earthquake intensity of VII on the European Macroseismic Scale (EMS-98) scale was experienced on the Maltese archipelago at least four times, with the major source of seismic hazard being the northern segment of the Malta Escarpment. Earthquake activity can also be attributed to active fault zones in the Sicily Channel and the Hellenic Arc. Even though the latter is situated relatively far away from the islands, an earthquake in 1856, with an epicentral location around 1000 km away from the islands, caused significant damage to buildings, with many houses suffering serious cracks to their walls (Galea, 2007). The public perception about seismic risk remains one of negligence and complacency and up to date, no comprehensive seismic site response study has been done on the islands. This study is the first of a series of site response analyses which are to be carried out. It is divided in two parts. Firstly, a series of ambient noise measurements were done at a site in Rabat (Malta) to investigate and evaluate different techniques for estimating one-dimensional shear-wave velocity profiles. The chosen site is characterised by outcropping Blue Clay overlying the harder Globigerina Limestone. The data from the first investigations then serve as input to the equivalent-linear analysis programme SHAKE2000 (Ordonez, 2002) which is used for the site response analysis. In this research work, some advantages and limitations of chosen surface-wave techniques are also assessed. Moreover, any difference between equivalent profiles (satisfying the same experimental data) in site response results is investigated.peer-reviewe

Preliminary assessment of the seismic vulnerability of load-bearing masonry buildings in Malta through numerical modelling

The seismic risk is Malta is perceived to be low, and no significant events have been recorded in recent years. In 1693, a major earthquake struck about 170 kilometres from Malta, devastating south-eastern Sicily, and causing serious damage in buildings in Malta with historical records of significant damage in Mdina but also in Valletta, Rabat and elsewhere.Research suggests that a similar earthquake on the same fault could occur every few hundred years. The present study is part of a wider research initiative in Malta focusing on the vulnerability of buildings to seismic activity including the vulnerability of unreinforced masonry buildings, their characteristics contributing to seismic vulnerability and their effect on the adjacent structures. [excerpt]peer-reviewe

The development of a rapid empirical seismic vulnerability assessment methodology for contemporary load-bearing masonry buildings in the Maltese Islands

According to historical records, the last major earthquake reported to have caused extensive damage in the MalteseIslands dates back to 1693. It is not possible to assess the vulnerability of masonry structures to seismic action through post-earthquake damage assessments. Considering a return period of 475 years, the probability of occurrence of a major seismic event is quite high. This study is an attempt at addressing the issue of the seismic response of the building stock in Malta. It focuses on the typical contemporary load-bearing masonry building typology. This typology mainly consists of blocks of apartments including a semi-basement with no internal walls and, in most cases, roofed over by hollow core precast prestressed planks, and with around 4 overlying residential floors in addition to a penthouse level.peer-reviewe

Enhancements of seafloor observatories and applications for natural hazard assessment and environmental monitoring

The final target of the MONSOON project (MONitoraggio SOttOmariNo for environmental and energetic purposes) is to build up a prototype of a new generation of seafloor observatory for which specific technological developments in terms of power consumption reduction, new data logger and new sensors have been planned. The project is carried out in the main frame of the wide range of scientific and technological activities developed by EMSO Research Infrastructure (European Multidisciplinary Seafloor and water-column Observatory, www.emsoeu.org). The new seafloor observatory is planned to operate either in stand-alone and real-time modes. The latter is possible with the connection to a surface buoy able to 1) provide (via modem) an internet connection to the sea-floor system and 2) communicate with the sea-floor observatory. The observatory is planned to be deployed down to a water depth of 2000m, even in an extreme marine environment, with the presence of hydrothermal vents. All the newly developed components of the observatory have been planned and laboratory-tested. In cooperation with the University of Malta a special activity is carried out to find out technical solutions for the detection of body and surface seismic waves and for the integration of specific seismic sensors into the multidisciplinary seafloor observatory. The purpose of that activity is the integration of a seismic sensor (either a short period or a broad band seismometer) in the same data acquisition system that manages the whole observatory in order to make the observatory able to be used in studies and monitoring activities in the georisks field. After a successful laboratory testing activity, experiments in a selected, real environment are planned. [excerpt]peer-reviewe