Sebastiano D’Amico

Evaluation of building fundamental periods and effects of local geology on ground motion parameters in the Siracusa area, Italy

The Siracusa area, located in the southeastern coast of Sicily (Italy), is mainly characterized by the outcropping of a limestone formation. This lithotype, which is overlain by soft sediments such as sandy clays and detritus, can be considered as the local bedrock. Records of ambient noise, processed through spectral ratio techniques, were used to assess the dynamic properties of a sample survey of both reinforced concrete and masonry buildings. The results show that experimental periods of existing buildings are always lower than those proposed by the European seismic code. This disagreement could be related to the role played by stiff masonry infills, as well as the influence of adjacent buildings, especially in downtown Siracusa. Numerical modeling was also used to study the effect of local geology on the seismic site response of the Siracusa area. Seismic urban scenarios were simulated considering a moderate magnitude earthquake (December 13th, 1990) to assess the shaking level of the different outcropping formations. Spectral acceleration at different periods, peak ground acceleration, and velocity were obtained through a stochastic approach adopting an extended source model code. Seismic ground motion scenario highlighted that amplification mainly occurs in the sedimentary deposits that are widespread to the south of the study area as well as on some spot areas where coarse detritus and sandy clay outcrop. On the other hand, the level of shaking appears moderate in all zones with outcropping limestone and volcanics.

A microtremor survey to define the subsoil structure in a mud volcanoes area: the case study of Salinelle (Mt. Etna, Italy)

Abstract A microtremor survey aiming to obtain information on subsoil structure was performed in the lower southwestern Etnean flank (Sicily, Italy). The area is characterized by emissions of muddy and salty water which create specific pseudo-volcanic edifices. Recording sites were both randomly selected in the area and along two profiles. Horizontal-to-vertical noise spectral ratio, polarization and surface wave prospecting techniques were used. The spectral ratios results set into evidence different frequency ranges that appear interesting to infer information on the subsoil structure. The depth of the hydrocarbon reservoir was inferred through 1D modeling, by using the information coming from the literature and experimental surveys. Moreover, a strongly directional effect suggests the existence of a NNW-SSE-oriented mud feeding dike.

The Easter Sunday 2011 Earthquake Swarm Offshore Malta: Analysis on Felt Reports

In the last forty years, Malta has only experienced a few occasional tremors from local or regional earthquakes, with only some being reported briefly in the local newspapers. These reports gave limited qualitative and quantitative information about the shaking experience felt across the islands. The Seismic Monitoring and Research Unit at the University of Malta has put in place a ‘Did you feel an earthquake?’ online questionnaire in order to start gathering information from locally felt earthquake related shaking. On Easter Sunday 24th of April 2011 windows rattled, doors shook open, and furniture shifted in many homes across Malta when a series of earthquakes occurred 38 km off the eastern coast. In total, the SMRU located 15 earthquakes with magnitudes ranging from M L 1.8 to 4.1 over a period of 4 days. A total of 489 felt reports were submitted through the online questionnaire. The compilation of the data is a first of its kind for the Maltese islands. Here we present a summary of the reports following the main shock. A maximum intensity value IV on the European Macroseismic Scale was assigned. No structural damage was reported. The data reflects the demographics as well as the different types of buildings found across the archipelago.

Earthquake and People: The Maltese Experience of the 1908 Messina Earthquake

On December 28, 1908 at 5:20 a.m. local time, a devastating earthquake (Mw = 7.2) struck Southern Italy along the Messina Strait (Fig. 1). This event caused severe ground shaking throughout the region and triggered a local tsunami. As result the cities of Messina along Sicily’s coast and Reggio di Calabria were completely destroyed (Baratta, 1910) causing more than 120,000 fatalities and with many left without shelter. The effects of the earthquake were felt within a 300-kilometer radius. Rescuers searched through the rubble for weeks, and people were still being pulled out alive days later, but thousands remained buried there. The 1908 earthquake had a significant impact on buildings and people and local communities which were displaced. The Maltese experience of the Messina 1908 earthquake relied on communication which reached Malta after the event. The assessment of the Maltese experience of the Messina Earthquake has so far been carried out with reference to published newspaper reports and other brief accounts including Herbert Ganado’s Rajt Malta Tinbidel. Alfons Maria Galea a Maltese author and filanthropist published a book in Maltese on the earthquake and its devastating effects in the popular educational series il-Kotba tal-Mogħdija taz-Żmien just a few weeks after the event. The book is a vivid account of the destruction caused by the earthquake, the suffering of the survivors and the reaction of the population in reviving the city. The document presents first-hand accounts of the events in sufficient detail to give a clear picture of the severity of the event, extents of the damage and impact on the population. It is mostly based on accounts received by Galea from persons in institutions including religious orders in Sicily who he knew. Newspaper reports in Malta and other countries together with Galea’s book present clear first-hand accounts of this event and provide information on the building deficiencies and damage, limitations of communication infrastructure during that period, limits to timely emergency response to support the population and emergency action at the beginning of the 20th century.

Earthquake ground-motion simulations for the Maltese Archipelago

The main goal of this paper is to provide earthquake ground motion simulations for particular earthquake scenarios, in terms of ground motion parameters for the Maltese islands. We used a stochastic approach to simulate high-frequency strong-ground motions, using an extended-source model code. This code was developed for earthquake simulations using stochastic finite-fault modelling and a dynamic corner frequency approach. The extended-source model code is a reliable and practical method to simulate ground motion records of moderate and large earthquakes especially in regions where structural damage is expected, but sparse ground motion recordings are available. In this paper, we show that in the Maltese archipelago, the ground motion from the repeat occurrence of historically recorded earthquakes, or from other potential sources, coupled with existing geological conditions and building typologies has the potential to cause significant structural damage in the area.

Prediction of High-Frequency Ground Motion Parameters Based on Weak Motion Data

This research was carried out using computational facilities procured through the European Regional Development Fund, Project ERDF-080 ‘A supercomputing laboratory for the University of Malta (http://www.um.edu.mt/research/scienceeng/erdf_080).

Mobile Spectroscopy in Archaeometry: Some Case Study

We provide an overview of recent results obtained by the innovative application of mobile spectroscopy for in situ investigation in archaeometry. Its growing relevance is linked to the great advantages of avoiding the transport and eventual damage of precious artifacts and of allowing the analysis of those specimens that are, for example, built into infrastructures or in some way permanently affixed. In this context, some case studies of combined instrumental approaches, involving X-ray fluorescence (XRF) and Raman spectroscopy, integrated by infrared thermography (IRT), are, in particular, discussed: the archaeological site of Scifi (Forza d’Agro, province of Messina, Italy) and the Abbey of SS. Pietro e Paolo d’Agro (Casalvecchio Siculo, province of Messina, Italy). In the first case, the elemental composition, as obtained by XRF, of two types of mortars belonging to two different chronological phases, dated back between the 3rd and the 5th century AD, allowed us to hypothesize a same origin area of their raw materials and a different production technique. Again, the combined use of XRF and Raman spectroscopies, supported by IRT technique, on pottery fragments of Greek-Hellenistic age and late imperial period, furnished important information concerning the receipts for the pigmenting agents of the finishing layer, allowing in some cases their unambiguous identification. In the second case, XRF data collected on bricks and stones from the external facade of the abbey allowed us to make some hypothesis concerning the provenance of their constituents materials, supposed to be in the area of valley of the river Agro.

Estimating Stability and Resolution of Waveform Inversion Focal Mechanisms

The main aim of this study is to describe several tools for testing the stability and resolution of waveform inversion focal mechanisms already successfully adopted for crustal earthquakes occurred in the Calabrian Arc region,

Coulomb Stress Changes in the Area of December 2013–January 2014 Sannio-Matese Seismic Sequence (Southern Italy)

The Italian Apennines are seat of extensional deformation, concentrated along the inner part of the mountain belt due to the opening of the Tyrrhenian back-arc basin during the late Miocene and the following rolling back subduction of Adriatic plate with an extension velocity of about 3 mm year−1 (D’Agostino et al. 2008; Faccenna et al. 2004). Apennines chain is a zone of high seismic hazard (http://zonesismiche.mi.ingv.it; “Mappa di pericolositasismica del territorionazionale”; D’Amico et al. 2013a) and it has been affected by a number of earthquakes in the past century suffering intensity X or higher several times in the past centuries (Boschi et al. 2000; CPTI Working Group 2004). The most recent examples are the 1980, M = 6.9, Irpinia events (Pino et al. 2008; Secomandi et al. 2013); the 1997–1998 Umbria-Marche (Caccamo et al. 2007) and the 2009 L’Aquila (D’Amico et al. 2010a, 2013b) sequences.

Quaternary Stress Field and Faulting in the Western Part of the Catanzaro Trough (Calabria, Southern Italy)

The Calabria Arc presents the highest probability of occurrence of major earthquakes in the Italian peninsula. Several destructive historical earthquakes (i.e. 1638, 1659, 1783, 1905 and 1908) affected, in particular, the Catanzaro Trough and its neighbouring areas. These events have been tentatively related to the activity of NE-SW trending normal faults. Some of these earthquakes have been followed by tsunamis, which caused further damages along the Tyrrhenian coast. In this paper, we reconstruct the Quaternary evolution of the Catanzaro Trough by combining field geo-structural and marine geophysical data. The results have been compared with existing database of earthquake focal mechanisms, updated with 8 new focal solutions performed in the present work. Analysis of faults offsetting the Lower-Middle Pleistocene deposits shows that the Catanzaro Trough experienced transcurrent and extensional phases of deformation. In particular, conjugate systems with NW-SE right-lateral and NE-SW left lateral faults were observed to displace the Lower Pleistocene deposits. Whereas NE–SW and N-S oriented normal faults have been identified as the main fault systems acting during late Pleistocene-Holocene phase. The interpretation of on-land structural datasets has been supported by geophysical data (multichannel and Chirp profiles) acquired in the offshore and onshore of the study area. Multidisciplinary approach has allowed to define NE-SW elongated sedimentary basins, as the Lamezia Basin, bordered on the one hand by Sant’Eufemia Fault that may extend up to 30 km-length, on the other hand by two overstepping faults, Vibo Valentia and San Pietro Lametino Faults. These findings carry some relevant implications in terms of seismic hazard, as they suggest that the longer fault segment, the greater its energetic seismic event. Finally, these data fit perfectly with the observed late Pleistocene-Holocene WNW-ESE extensional stress regime derived from existing and new database of earthquake focal mechanisms. This is in agreement with the orientation of the most seismically active grabens of the Calabrian Arc (the Crati, the Mesima and the Gioia Tauro Basins). Amongst these structural lineaments, the NE-SW and N-S trending normal faults play surely a relevant role as part of recent seismotectonics processes controlling the Late Quaternary geodynamics of the central Calabrian Arc, representing the source of the main destructive earthquakes occurred in the region.