Reliable ground-motion measurements are essential for seismic hazard assessment and require seismological stations to be installed in free-field conditions, away from structural interferences. However, global network analyses show diverse installation configurations that can affect measurements. Although topographic effects are natural, their influence can extend over several meters, making them closely related to operators' installation choices. Although summit effects are well studied and known to cause strong amplifications, the impact of cliffs or escarpments remains less explored. In this study, 16 SmartSolo IGU-16HR 3C nodes were placed on either side of a 30-m cliff located in Cephalonia (western Greece), for 4-10 months, recording 307 low-to-moderate-magnitude seismic events. The main results reveal that de-amplifications recorded at the cliff base are greater than amplifications determined at the cliff top, particularly between 5 and 15 Hz. This study shows that amplification and de-amplification are primarily driven by topography, whereas their directional dependence is likely shaped by both topographic and lithologic factors. Furthermore, the anisotropy related to cliff fracturing interacts with the effects of source back azimuth. Amplification and de-amplification can be correctly predicted using the frequency-scaled curvature (FSC) and illuminated FSC proxies, provided that an exponential functional form is used for determining de-amplifications at the base of near-vertical cliffs. Furthermore, the azimuthal dependence observed, inducing strong de-amplifications depending on the direction observed, seems related more to the anisotropy of geologic formations than to the cliff topography itself. These effects should be considered when using data from stations in similar topographic settings. Neglecting them can bias ground-motion models and underestimate earthquake magnitudes, particularly for stations at the base of cliffs. From these considerations, we strongly recommend installing future seismological stations a few tens of meters away from the bases and ridges of even small cliffs or escarpments.
Heritage buildings represent tangible links between present and past; embody the creativity and traditions from past generations. The distinctive character of these buildings, primarily expressed through their authenticity and inherited values, emphasizes the need for innovative and carefully adapted conservation approaches. In this context, the present study explores the potential and limitations of non-destructive techniques (NDTs) in the diagnosis and conservation of cultural heritage buildings. By presenting relevant examples from professional literature, the role of NDTs to support sustainable conservation goals is demonstrated.
Unreinforced masonry structures (URM) are prevalent in under- developed and developing countries. The majority of these URM structures are not engineered, they simply follow local construction techniques and usually do not comply to any seismic standards. After a thorough description of the methods of construction and the materials used for URM buildings all over the world, the most common seismic damage and failures types for each system are presented and explained through figures and actual case study pictures. Then the book focuses on the low-cost repair, strengthen-ing and retrofitting tailored for non-engineered (URM) buildings in seismic-prone regions. Emphasizing on local and global stability, it encompasses a diverse spectrum of strengthening approaches. Each technique is meticulously described, providing insights into its range of applications, the basic scientific concept and key con-siderations for the design and the application process. Through meticulous planning and execution, these techniques enhance seismic resilience while considering factors such as building con-dition, seismic hazard, and cultural significance. This state-of-the-art document encompasses the knowledge as -similated from the effect of past seismic events on different types of URMs and aims to empower communities in safeguarding lives and heritage against seismic hazards providing solutions both cost-effective and comprehensive. It focuses on low-cost seismic repair, strengthening and retrofitting techniques, considering the main URM structural typologies and respective seismic failures in under-developed and developing countries and could serve as a useful tool for practical engineers and designers.
Abstact In this study site characterization of twelve accelerometer station sites of the Hellenic Accelerometers Network (HAN) is presented. An established European protocol is applied that consists of non-invasive active (Multichannel Analysis of Surface Waves: MASW) and passive (Ambient Vibration Analysis: AVA) methods. Data processing is carried out systematically, using new techniques of dispersion curves estimation and their inversion to obtain 1D shear wave velocity profiles at the examined sites. Surface geology and other site information previously indicated six sites as reference “rock” and six as stiff to soft soil. After data processing in this study, it was determined that only five of them fulfil the engineering bedrock criterion (\(\:{V}_{S30}\) > 800 m/s), with one of them - station ART2 (Arta) - identified as very hard rock (\(\:{V}_{S30}\) ~2000 m/s). The remaining seven investigated sites fall within stiff to soft soil categories (380 ≤ \(\:{V}_{S30}\) ≤ 618 m/s). The results show that, for stiff soil and rock sites, geology and topographic slope- inferred \(\:{V}_{S30}\) values, in some cases significantly, especially for \(\:{V}_{S30}\) > 500 m/s. These results highlight the importance of direct geophysical investigation for reliable site classification and for reducing bias in ground motion modeling, e.g. Ground-Motion Models (GMMs) and Generalized Inversion Techniques (GITs). The updated station sites characterization metadata set provides a reference framework for future updates of the Hellenic Accelerometers Network recordings and contributes to the harmonization of European strong-motion stations metadata within EPOS as well as in the European Strong Motion database.
This chapter delves into the comprehensive array of repair, strengthening, and retrofitting techniques tailored for non-engineered unreinforced masonry (URM) buildings in seis-mic-prone regions. Emphasizing local and global stability, it encompasses a diverse spec-trum of strengthening approaches, ranging from repointing to advanced solutions such as ring beams and tie rods. Each technique is meticulously detailed, providing insights into its range of applications, application processes, and key considerations. Through meticulous planning and execution, these techniques enhance seismic resilience while considering fac-tors like building condition, seismic hazard, and cultural significance. With a commitment to cost-effectiveness and accessibility, this chapter aims to empower communities in safe-guarding lives and heritage against seismic hazards.
