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In the present paper, we analyse ground tilt and seismicity at Campi Flegrei caldera and Ischia Island, two volcanic areas located in the south of Italy. These areas have been well studied for many years from a petrological, volcanological and geophysical view point. Moreover, due to the high seismic and volcanic risk for the populations living there, they are continuously monitored by networks of geophysical and geochemical sensors. We summarize the most important results that we obtained so far, concerning the observations of relationships between seismic activity and ground tilt anomalies, focusing on the time interval 2015&ndash, 2018. First, we present a detailed description of the tiltmeter and seismic networks in both the investigated areas, as well as their development and improvement over time that has enabled high quality data collection. From the joint analysis of the seismic and borehole tiltmeter signals, we often notice concurrence between tilt pattern variations and the occurrence of seismicity. Moreover, the major tilt anomalies appear to be linked with the rate and energy of volcano-tectonic earthquakes, as well as with exogenous phenomena like solid Earth tides and hydrological cycles. The analysis that we present has potential applicability to other volcanic systems. Our findings show how the joint use tilt and seismic data can contribute to better understanding of the dynamics of volcanoes.

Seismic isolation is an effective method for the protection of buildings and their contents during strong earthquakes. This research work aims to assess the appropriateness of the linear and nonlinear models that can be used in the analysis of typical low-rise base isolated steel buildings, taking into account the inherent nonlinearities of the isolation system as well as the potential nonlinearities of the superstructure in case of strong ground motions. The accuracy of the linearization of the isolator properties according to Eurocode 8 is evaluated comparatively with the corresponding response that can be obtained through the nonlinear hysteretic Bouc-Wen constitutive model. The suitability of the linearized model in the determination of the size of the required seismic gap is assessed, under various earthquake intensities, considering relevant methods that are provided by building codes. Furthermore, the validity of the common assumption of elastic behavior for the superstructure is explored and the alteration of the structural response due to the inelastic deformations of the superstructure as a consequence of potential collision to the restraining moat wall is studied. The usage of a nonlinear model for the isolation system is found to be necessary in order to achieve a sufficiently accurate assessment of the structural response and a reliable estimation of the required width of the provided seismic gap. Moreover, the simulations reveal that the superstructure`s inelasticity should be taken into account, especially if the response of the structure under high magnitude earthquakes is investigated. The consideration of the inelasticity of the superstructure is also recommended in studies of structural collision of seismically isolated structures to the surrounding moat wall, since it affects the response.

The current paper presents an efficient methodology for numerically simulating in three dimensions adjacent buildings that may experience pounding during strong earthquakes. In particular, a new approach to the numerical problem of spatial impact modeling that does not require the 'a priori' determination of the contact points is presented, taking also into account the geometry at the vicinity of an impact. In the current study, the buildings are simulated as linear multi-degree-of-freedom-systems, but the methodology can be easily extended to consider nonlinear behavior as well. A software application has been specifically developed to implement the proposed methodology, using modern object-oriented design and programming. The developed software is utilized in a simple example, and the computed results are compared with the corresponding analysis results obtained from a commercial general-purpose software application that uses typical contact elements for the simulation of impacts. A discussion follows on the advantages and capabilities of the proposed methodology and the developed software. Copyright copyright 2013 John Wiley & Sons, Ltd. 43 7 985 1003

SUMMARY During strong earthquakes, structural poundings may occur between adjacent buildings because of the limited separation distance and the deformations of their stories. A potential mitigation measure for this problem is the incorporation of layers of soft material, such as rubber, which can act as collision bumpers, in order to prevent the sudden impact pulses. In an effort to investigate the effectiveness of such an impact mitigation measure, relevant numerical simulations and parametric studies can be performed. However, none of the known impact models, which are available in the literature, is able to represent the usage of rubber bumpers with sufficient accuracy. The current study presents a simple but efficient methodology that can be used to simulate the incorporation of rubber layers between neighboring structures with relatively narrow seismic gaps. Such methodology will enable us to numerically investigate the effectiveness of using rubber bumpers to mitigate potential earthquake-induced pounding. In particular, a new nonlinear inelastic force-based impact model, able to appropriately describe the behavior of rubber under impact loading, taking also into account the limited thickness of the bumper, is introduced. Finally, a numerical example of simulating earthquake-induced pounding between two multistory buildings with the consideration of rubber bumpers at impact locations is presented. Copyright [copy 2012 John Wiley & Sons, Ltd. 42 1 81 100

This paper presents selected indicative results from an extensive parametric investigation that has been performed in order to assess the effects of potential earthquake-induced poundings on the overall dynamic response of seismically isolated buildings. In particular, a seismically isolated building and its adjacent fixed-supported buildings are subjected to various earthquake excitations that induce structural impact among the buildings in series. The results indicate that the seismically isolated building may hit against the adjacent buildings at the upper floor levels before the occurrence of any pounding at the isolation level with the surrounding moat wall. The severity of the impact depends on the dynamic properties of the adjacent buildings, in combination with the earthquake characteristics. Copyright © 2009 John Wiley & Sons, Ltd.

In this research work, the Discrete Element Methods (DEM) is utilized to investigate the response of ancient multi-drum columns during harmonic and earthquake excitations by simulating the individual rock blocks as distinct rigid bodies. The drums can undergo rocking either individually or in groups resulting in several different and alternating shapes of oscillations. A specialized software application has been developed, using modern object-oriented programming technologies and computer graphics to effectively perform efficient seismic simulations of multi-block structures. The contact stiffness and damping coefficients are estimated by performing small scale experiments and comparing the response with a corresponding numerical simulation. The effect of the coefficient of friction is numerically examined, since its value can significantly influence the overall response. The sliding effect under dynamic loading is examined both experimentally and numerically. Using the developed software, parametric simulations of multi-drum columns are performed in order to investigate and understand the influence of different characteristics of earthquake excitations as well as the various mechanical and geometrical characteristics of these structures on their seismic response. Furthermore, columns with an epistyle are examined under harmonic excitations, in order to assess the influence of the excitation frequency and the number of drums that compose each individual multi-drum column on the dynamic behavior and response of a colonnade.

In this paper, the seismic behavior of ancient monumental structures with monolithic or multi-drum classical columns is investigated. In particular, the Discrete Element Methods (DEM) are utilized in the study of ancient columns under strong ground excitations, by simulating the individual rock blocks as distinct bodies. A specialized software application has been developed, using modern object-oriented technologies and computer graphics. A large number of parametric studies has been performed in order to investigate the effect of certain parameters on the response of multi-drum columns. Specifically, the influence of the peak ground acceleration and the excitation frequency under harmonic excitations is examined, using small-scale experiments and numerical simulations. The value of the peak ground acceleration that is needed to initiate either sliding or rocking of multi-drum columns was found to decrease with the increase of the frequency of a harmonic excitation. Conversely, the simulations indicate that multi-drum columns are significantly more vulnerable to collapse at low-frequency excitations, which do not commonly occur in the Eastern Mediterranean region where most of these monuments can be found. 30 8 2154 2164

International audience; Off-fault seismogenic deformation in sediments (seismites) has proved useful for recovering long continuous records of earthquake activity. An important example of seismite is clastic dikes that were formed 'dynamically' by fracturing of the host rock and injection of clastic materials. However, they are easily confused with 'passive' dikes that were filled by deposition into preexisting fissures. This study demonstrates the application of anisotropy of the magnetic susceptibility (AMS) analyses to recognition of seismites. We assume that different sources of dike fill have different microfabrics, which manifest in different magnetic fabrics. To test this hypothesis we studied over 250 Holocene clastic dikes, exposed by deep incision into the lacustrine 70-15 ka Lisan Formation in the Dead Sea basin. Typically, they are vertical, up to 30-40 m high, and up to 0.4 m thick. In map view they appear in a radial arrangement spanning a sector of 60 degrees with projected strikes that converge at a structural dome above a rising salt diapir. Field relations and AMS analyses show that 'passive' dikes filled from above have vertical Kmin directions, compatible with sedimentary features. Conversely, horizontal to sub-horizontal Kmin directions occur in dikes that show segmentation typical of horizontal propagation of the fractures and lateral material transport. Vertical zoning of the clay and silt is interpreted as evidence of multiple injection events. Optical Stimulation Luminescence (OSL) ages, spanning 7-14 ka, are in agreement with dike truncation by undisturbed late Holocene alluvium. We conclude that the upward indentation of a salt diapir induced a local stress perturbation, which triggered the formation of a radial set of fractures. Subsequently the fractures were filled by horizontal injection of fine elastics pressurized by earthquake vibrations. Sedimentation from above occurred where the tops of the dikes reached the surface and remained open.

Seismic isolation can significantly reduce the induced seismic loads to a relatively stiff building by inserting flexibility at its base to avoid resonance with the predominant frequencies of common earthquakes. Sometimes the width of the provided seismic gap to facilitate the large relative displacements at the isolation level of a seismically isolated building is limited. Hence, there is a possibility of poundings of the building with adjacent structures during strong earthquakes. This work investigates, through numerical simulations using a specially developed software, how potential poundings of seismically isolated buildings with adjacent structures affects the effectiveness of seismic isolation. 86 7-8 618 626