MISURE IN SITU DELLE CARATTERISTICHE ELASTICHE ED ANELASTICHE DEI TERRENI DALL'INVERSIONE DELLE RELAZIONI DI DISPERSIONE DELLE ONDE SUPERFICIALI

1994/1995VIII Ciclo1965Versione digitalizzata della tesi di dottorato cartacea

Site Effects in the Eastern Po Plain by Mean of Weak and Strong Earthquakes

We present the activities carried out within the S2 2012-2013 Project, funded in the frame of DPCINGV Agreement, that concerns the mid-long term Seismic Hazard Assessment in Italy on two priority areas, the Po Plain and the Southern Italy. The Po Valley, an area hitherto considered of low seismological interest, has attracted the attention of the seismological community following the events of May 20, 2012. The day after the main shock that stuck eastern Emilia in 2012, the OGS - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale deployed a temporary seismographic network in the Ferrara area. All the investigated locations were set on soft soils. The large amount of collected data allowed comparison between observed PGA and theoretical predictions, ShakeMaps and attenuation laws, but the lack of a reference site during the 2012 recordings did not allow for estimating the amplification factor. In order to accomplish this task, in February 2013, a new 5 stations recording array acquired data at four of the 2012 network sites and at the Casaglia reference site, north of Ferrara, where a borehole Very Broad-Band station is coupled with a midperiod sensor at the surface. This borehole reference station made possible the estimation of site amplification of the 2013 array sites. The reference methods allowed an easier identification of the resonance frequency, which peaks appear sharper than what displayed by single-station methods (both H/V on ambient noise and earthquakes), and relative soil amplification. A large amount of original seismological data has been recorded in a poorly instrumented area, including significant events of the 2012 Emilia and 2013 Lunigiana sequences. The entire dataset of continuous waveforms has been made available on the OGS web based OASIS Database, from the earliest stages of the project. For the largest events strong-motion parameters were calculated and published on the OASIS database. Event time series and metadata (site monographs) are available similarly to the ITACA Database

Seismic hazard for the Trans Adriatic Pipeline (TAP). Part 2: broadband scenarios at the Fier Compressor Station (Albania)

AbstractTo ensure environmental and public safety, critical facilities require rigorous seismic hazard analysis to define seismic input for their design. We consider the case of the Trans Adriatic Pipeline (TAP), which is a pipeline that transports natural gas from the Caspian Sea to southern Italy, crossing active faults and areas characterized by high seismicity levels. For this pipeline, we develop a Probabilistic Seismic Hazard Assessment (PSHA) for the broader area, and, for the selected critical sites, we perform deterministic seismic hazard assessment (DSHA), by calculating shaking scenarios that account for the physics of the source, propagation, and site effects. This paper presents a DSHA for a compressor station located at Fier, along the Albanian coastal region. Considering the location of the most hazardous faults in the study site, revealed by the PSHA disaggregation, we model the ground motion for two different scenarios to simulate the worst-case scenario for this compressor station. We compute broadband waveforms for receivers on soft soils by applying specific transfer functions estimated from the available geotechnical data for the Fier area. The simulations reproduce the variability observed in the ground motion recorded in the near-earthquake source. The vertical ground motion is strong for receivers placed above the rupture areas and should not be ignored in seismic designs; furthermore, our vertical simulations reproduce the displacement and the static offset of the ground motion highlighted in recent studies. This observation confirms the importance of the DSHA analysis in defining the expected pipeline damage functions and permanent soil deformations

Massive earthquake swarm driven by magmatic intrusion at the Bransfield Strait, Antarctica

An earthquake swarm affected the Bransfield Strait, Antarctica, a unique rift basin in transition from intra-arc rifting to ocean spreading. The swarm, counting ~85,000 volcanotectonic earthquakes since August 2020, is located close to the Orca submarine volcano, previously considered inactive. Simultaneously, geodetic data reported up to ~11 cm northwestward displacement over King George Island. We use a broad variety of geophysical data and methods to reveal the complex migration of seismicity, accompanying the intrusion of 0.26-0.56 km³ of magma. Strike-slip earthquakes mark the intrusion at depth, while shallower normal faulting the ~20 km long lateral growth of a dike. Seismicity abruptly decreased after a Mw 6.0 earthquake, suggesting the magmatic dike lost pressure with the slipping of a large fault. A seafloor eruption is likely, but not confirmed by sea surface temperature anomalies. The unrest documents episodic magmatic intrusion in the Bransfield Strait, providing unique insights into active continental rifting

Hacia los orígenes de la concentración mediática en Argentina

Este artículo se propone examinar críticamente los inicios del proceso de concentración me - diática en Argentina, por medio del estudio de las políticas de comunicación implementadas en el marco de la adopción del modelo económico neoliberal. Para ello se realiza un análisis de la conformación accionaria y de la evolución en términos de facturación y ranking empre - sarial de los grupos mediáticos que obtuvieron las licencias de los canales de televisión abierta de la Ciudad de Buenos Aires tras su paso a manos privadas. Se evalúa en qué medida las características particulares de esta privatización redundaron en beneficios económicos para las empresas adjudicatarias e influyeron en la configuración del mapa de medios argentino

A Python Code for Detecting True Repeating Earthquakes from Self‐Similar Waveforms (FINDRES)

Seismic data are generally scrutinized for repeating earthquakes (REs) to evaluate slip rates, changes in the mechanical properties of a fault zone, and accelerating nucleation processes in foreshock and aftershock sequences. They are also used to study velocity changes in the medium, earthquake physics and prediction, and for constraining creep rate models at depth. For a robust detection of repeaters, multiple constraints and different parameter configurations related to waveform similarity have been proposed to measure cross‐correlation values at a local seismic network and evaluate the location of overlapping sources. In this work, we developed a Python code to identify REs (FINDRES), inspired by previous literature, which combines both seismic waveform similarity and differential S‐P travel time measured at each seismic station. A cross‐spectral method is applied to evaluate precise differential arrival travel times between earthquake pairs, allowing a subsample precision and increasing the capacity to resolve an overlapping common source radius. FINDRES is versatile and works with and without P‐ and S‐wave phase pickings, and has been validated using synthetic and real data, and provides reliable results. It would contribute to the implementation of open‐source Python packages in seismology, supporting the activities of researchers and the reproducibility of scientific results

Seismicity at the Castor gas reservoir driven by pore pressure diffusion and asperities loading

We are thankful to Dr. J. V. Cantavella and IGN for providing waveform data and metadata of the network ES. S.C. and P.N. received funding by the European Union RFCS project PostMinQuake grant 899192. J.A.L.-C. was financed by the European Union's Horizon 2020 research and innovation program under the Marie Skodowska-Curie grant agreement 754446 and UGR Research and Knowledge Transfer Found-Athenea3i and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Projektnummer (407141557). D.S. received funding by the Spanish National FEDER/MINECO Project PID2019-109608GB-I00/AEI/10.13039/501100011033, FEDER/Junta de Andalucia project A-RNM-421-UGR18 and Research group RNM104 of the Junta de Andalucia. F.G. was financed by the European Union's Horizon 2020 Framework Programme under the Marie Skodowska Curie Grant agreement (790900).The 2013 seismic sequence at the Castor injection platform offshore Spain, including three earthquakes of magnitude 4.1, occurred during the initial filling of a planned Underground Gas Storage facility. The Castor sequence is one of the most important cases of induced seismicity in Europe and a rare example of seismicity induced by gas injection into a depleted oil field. Here we use advanced seismological techniques applied to an enhanced waveform dataset, to resolve the geometry of the faults, develop a greatly enlarged seismicity catalog and record details of the rupture kinematics. The sequence occurred by progressive fault failure and unlocking, with seismicity initially migrating away from the injection points, triggered by pore pressure diffusion, and then back again, breaking larger asperities loaded to higher stress and producing the largest earthquakes. Seismicity occurred almost exclusively on a secondary fault, located below the reservoir, dipping opposite from the reservoir bounding fault.European Union RFCS project PostMinQuake grant 899192European Union's Horizon 2020 research and innovation program under the Marie Skodowska-Curie grant 754446UGR Research and Knowledge Transfer Found-Athenea3iGerman Research Foundation (DFG) 407141557Spanish National FEDER/MINECO Project PID2019-109608GB-I00/AEI/10.13039/501100011033FEDER/Junta de Andalucia project A-RNM-421-UGR18Junta de Andalucia RNM104European Union's Horizon 2020 Framework Programme under the Marie Skodowska Curie Grant 79090

Seismicity Rate Changes and Geodetic Transients in Central Apennines

Using template matching and GPS data, we investigate the evolution of seismicity and observable deformation in Central Apennines. Seismicity appears more persistent at the base of the seismogenic layer than in the shallower crust. Diffuse activity is reported on segments at depth, alternating along strike with apparent quiescence on segments that experienced one or more Mw6+ earthquakes in 1997, 2009, and 2016. Central Apennines are likely underlain by a sizeable shear zone with areas of diffuse seismicity bounding shallow normal faults where Mw6+ earthquakes occurred. The deformation observed at the surface seems to follow the seismicity variations at the base of seismogenic layer along the Apenninic chain. Principal and independent component analyses of GPS data exhibit a transient when the 2016 foreshock sequence starts. This transient propagated northward from the Campotosto fault up to the Alto Tiberina fault system and has likely loaded the Mw6+ 2016 earthquake sequence