Scientific Programs

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The research involved in this SEIVAS project (http://civilgeo.teicm.gr/index.php?cat_id=55) concerns a full scale study for the building stock located in the city of Serres (Greece), aiming at a reliable estimation of seismic losses and thus the rational and effective treatment of seismic risk.

The first phase of this project involves the estimation of seismic hazard in the greater area of Serres and the development of a series of seismic scenarios that correspond to various levels of seismic action. Furthermore, utilizing state-of-the-art techniques, the soil profile is identified in several locations of the city, allowing the estimation of the strong ground motion and the development of the corresponding response spectra.

The next phase of the project involves the inventory of a reliable sample from the building stock in Serres and the development of a database with all building characteristics that affect their seismic response. Moreover, seismic vulnerability functions will be developed, utilizing Greek as well as international experience, tailored to the special characteristics of the buildings present in Serres. Finally, combining the outcome of the aforementioned actions, a series of seismic risk scenarios for the building stock will be developed and distributed including the estimated losses in monetary terms as well as predictions for the post-earthquake tagging of the buildings.

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In this project we compare and evaluate different surface geophysical methods in order to estimate the dynamic properties of the subsurface. Those methods are applied in situ and not in the lab without changing the earth's material.

Additionally, they are cost effective and fast to implement on the field since a borehole is not necessary. Finally, they are of great interest since they can be used in a massive number of applications (geotechnical research, building subsidence, Microzonation, ground motion prediction equations, loss estimation in case of an earthquake).

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The E2VP-2 project (http://www.nuquake.eu/Projects/E2VP2-organigramme.pdf) is the continuation of a project launched in 2007 by the Cashima Project and which aimed to evaluate the reliability of numerical simulations when they are used to reproduce observed site effect phenomenon in complex geometries (E2VP-1, phase 1). The phase 2 of this project (2012-2015) will continue the work begun during the first phase, mainly on the "validation" part. This will include examining whether the gap between simulation and actual data observed in "phase 1" may be reduced by working on the seismic source parameter and the geometric and geotechnical site. For the "phase 2", improvement of source parameters and geological description of the basin will be carried out by EPPO-ITSAK in collaboration with AUTH-Geophysical Laboratory as well as identification/quantification of the different sources of uncertainty will be attempted. The scope of the work includes a twofold action aiming at decreasing uncertainties involved in various steps better understanding and validating results of 3D ground motion simulation. The two parallel actions can be are described in the following two Work Packages:

• Contribution to the construction of an updated geological and geotechnical model of the site and help in the preparation of the E2VP-2 sensitivity studies concerning geological and geometrical aspects
• Contribution to the optimization of the source parameter definition of recorded earthquakes, providing signals of all available recorded intermediate to long distance earthquakes (30km≤R≤200km) and contribution to the preparation of the E2VP-2 sensitivity studies concerning the source parameter aspects

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Primary scientific goal of this project is the establishment of novel measurement strategies for an efficient structural imaging of shallow and medium depth sedimentary environments using noise correlation tomography (NCT). The NCT has become an important tool within passive seismic observation campaigns and is based on a simple statement from the theory of diffuse wave fields. This statement says that the correlation of the observations at two spatially separated recording stations images the propagation properties of the medium in between those stations.

In practice, given the characteristics of the seismic background ambient vibration wave field and the position of seismological recording equipment on the surface of the Earth, on observes usually the surface wave portion in the correlation results. If one chooses to evaluate all two-station combinations of a network recording, it is possible to apply tomographic imaging techniques using distinct periods of the observed surface waves and thus allows sensing different depths of the medium.

Currently experiments are optimized to long term recordings for obtaining best signal to noise ratios in the analysis results. At small spatial scales and industrial type applications (geotechnically relevant dimensions for structural engineering projects / seismological site characterization), however, it is of considerable interest to find optimal measurement strategies which minimize experiment time while at the same time do maintain the tomographic imaging quality and thus allows for 3D structural interpretation at reasonable cost.

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The NERA project (http://www.nera-eu.org/) integrates key research infrastructures in Europe for monitoring earthquakes and assessing associated hazard and risk. The project aim is to achieve an integration that significantly facilitates cross discipline assessment of hazard and risk assessment and reduce vulnerability of constructions and citizens to earthquakes. NERA's long-term objective is to integrate seismic and engineering infrastructures and thus establish an effective integrated network of European research infrastructures for earthquake risk assessment and mitigation. NERA's strategy is to combine expertise in observational and strong ground motion seismology, modelling, geotechnical and earthquake engineering and information technology. Within NERA they develop multidisciplinary advanced infrastructures facilitating integrated data and product access and use of the data to a broad scientific public. Its activities take optimal advantage of developments within other relevant EC-projects and European and global initiatives, contributing among others to the ESFRI EPOS infrastructure and the OECD GEM program. NERA is organised along a number of working packages/activities:

• Cooperative actions (Networking Activities),
• RTD actions (Joint Research Activities),
• Transnational Access and
• Service Activities.