Andrea Morelli

National Institute of Geophysics and Volcanology | INGV · Sezione di Bologna

We present preliminary results about the density structure of the mantle below the Euro-Mediterranean area, down to 1000 km depth. The velocity variations of the P-wave tomography of the Alpine-Mediterranean area (PM0.5, Piromallo and Morelli, 2003), together with the Bouguer anomalies of the satellite-derived GGM02C (Tapley et al., 2005) high-reso...

We present a new 3-D transversely isotropic shear wave velocity model of the European and Mediterranean upper mantle obtained by analysis of surface waves. Data used are fundamental-mode Rayleigh and Love group velocity measurements in the period range 35–170 s, taken on seismograms recorded by European stations for regional earthquakes. The tomogr...

We present a new crustal model for the European Plate, derived from collection and critical integration of information selected from the literature. The model covers the whole European Plate from North Africa to the North Pole (20N-90N) and from the Mid-Atlantic Ridge to the Urals (40W-70E). The chosen parametrization represents the crust in three...

Underdetermination is a condition affecting all problems in seismic imaging. It manifests mainly in the nonuniqueness of the models inferred from the data. This condition is exacerbated if simplifying hypotheses like isotropy are discarded in favor of more realistic anisotropic models that, although supported by seismological evidence, require more...

Rayleigh wave ellipticity measurements from seismic ambient noise recorded on the Greenland Ice Sheet (GrIS) show complex and anomalous behavior at wave periods sensitive to ice (T < 3–4 s). To understand these complex observations, we compare them with synthetic ellipticity measurements obtained from synthetic ambient noise computed for various se...

Seismic Rayleigh wave ellipticity measurements are the horizontal-to-vertical ratio of the Rayleigh wave particle motion, and are sensitive to the subsurface structure beneath a seismic station. H/V ratios measured from the ambient vibrations of the Earth are being increasingly used in glaciological applications to determine glacier and ice sheet t...

In this study, we explore the impact of using different Moho surfaces on the reconstruction of the upper mantle geophysical parameters. The study area is the subsurface of the Antarctica continent. Using the optimization program of Sequential Integrated Inversion (SII) and the gravity anomalies synthetized by a global Gravity Field Model (GFM), we...

We use geophysical data together with a recent subglacial bedrock map (BEDMACHINE model) to obtain and investigate a new three-layer sediment model for Antarctica that locally improves the global sediment model. We provide a combined, continuous, sediment model for Antarctica and surrounding oceans by joining such improved continental sedimentary m...

We present the first three‐dimensional (3D) anisotropic teleseismic P‐wave tomography model of the upper mantle covering the entire Central Mediterranean. Compared to isotropic tomography, it is found that including the magnitude, azimuth, and, importantly, dip of seismic anisotropy in our inversions simplifies isotropic heterogeneity by reducing t...

The Western Alps shows a complex crustal organization due to the subduction of the European plate beneath the Adriatic plate and exhumation of the mantle wedge. The lithospheric structure of the Western Alps, that may hold significance for understanding orogenic processes and evolution, has been the subject of many geophysical studies, but the Moho...

The flow of the Greenland Ice Sheet is controlled by subglacial processes and conditions that depend on the geological provenance and temperature of the crust beneath it, neither of which are adequately known. Here we present a seismic velocity model of the uppermost 5 km of the Greenlandic crust. We show that slow velocities in the upper crust ten...

In this paper we describe the results of an experimental implementation of the recent guidelines issued by the Italian regulatory body for monitoring hydrocarbon production activities. In particular, we report about the pilot study on seismic, deformation, and pore pressure monitoring of the Mirandola hydrocarbon cultivation facility in Northern It...

We report on a passive seismic experiment on a historical tower in northern Italy. Assessment of dynamical properties of such structures is known to be very important to anticipate their response to possible earthquake excitation. We show how classical seismological analyses can image, in high definition and detail, many modes of vibra- tion, conti...

We compile existing seismic, gravity, radar and magnetic data, together with the subglacial bedrock relief from the BEDMACHINE project, to build the most detailed sediment model for Antarctica. We interpolate these data according to a tectonic map of Antarctica using a statistical kriging method. Our results reveal significant sediment accumulation...

A number of oil- and gas-producing leases have been operating in Italy in the last decades, many of which are located in the surroundings of tectonically active regions. Identifying human-induced seismicity in areas with high levels of natural seismicity is a difficult task for which virtually any result can be a source of controversy. We implement...

We study the crustal velocity changes occurred at the restart of produced water injection at a well in the Val d'Agri oil field in January–February 2015 using seismic noise cross-correlation analysis. We observe that the relative velocity variations fit well with the hydrometric level of the nearby Agri river, which may be interpreted as a proxy of...

Paper already published. Preprint file replaced by published article.

We use seismic data together with a subglacial bedrock relief from the BEDMAP2 database to obtain a new three-layer model of the consolidated (crystalline) crust of Antarctica that locally improves the global seismic crustal model CRUST1.0. We collect suitable data for constructing crustal layers, analyse them and build maps of the crustal layer th...

Public concern about anthropogenic seismicity in Italy first arose in the aftermath of the deadly M ≈ 6 earthquakes that hit the Emilia-Romagna region (northern Italy) in May 2012. As these events occurred in a (tectonically active) region of oil and gas production and storage, the question was raised, whether stress perturbations due to undergroun...

Earthquake hypocentral location is perhaps the most classical problem in seismology, the solution of which is often affected by significant uncertainty. In monitoring the effects of underground anthropogenic activities, the earthquake hypocentral location, magnitude, and ground motions are important parameters for managing induced seismicity (as e....

The densely populated Po Plain, a very deep sedimentary basin in northern Italy, is prone to heavy shaking during earthquakes. Seismic hazard assessment must account for local variation in wave amplification. Standard ground motion prediction equations may fail to picture the complexity of strong lateral gradients in seismic response, due to sharp...

In 2014, the Italian Ministry of Economic Development published monitoring guidelines (ILG) describing in detail the governmental regulations for geophysical monitoring in areas interested by exploitation of underground potentials. The ILG prescribe the monitoring of microseismicity, ground deformation and pore pressure near the industrial activiti...

In data 4 maggio 2018, tra il Ministero dello Sviluppo Economico – Direzione Generale per la sicurezza delle attività minerarie ed energetiche (DGS-UNMIG), l’Istituto Nazionale di Geofisica e Vulcanologia (INGV) e Assomineraria, è stato siglato un Accordo Quadro per l’attività di collaborazione scientifica. Successivamente, in data 17 maggio 2018,...

In Italy, the discussion about anthropogenic seismicity started after the deadly M6 Emilia earthquakes in 2012. Occurring these events in an area of gas and oil production, the question raised, whether stress perturbations induced by the exploitation may have triggered these events. In 2014, the Government published monitoring guidelines (ILG) desc...

In data 4 maggio 2018, tra il Ministero dello Sviluppo Economico – Direzione Generale per la sicurezza delle attività minerarie ed energetiche (DGS-UNMIG), l’Istituto Nazionale di Geofisica e Vulcanologia (INGV) e Assomineraria, è stato siglato un Accordo Quadro per l’attività di collaborazione scientifica. Successivamente, in data 17 maggio 2018,...

We develop a new method for measuring ellipticity of Rayleigh waves from ambient noise records by degree-of-polarization (DOP) analysis. The new method, named DOPE , shows a good capability to retrieve accurate ellipticity curves separated from incoherent noise. In order to validate the method we perform synthetic tests simulating noise in a 1D Ear...

In recent years, great efforts have been devoted to the study of the human-induced earthquakes, owing to the effect that these earthquakes can have in terms of seismic hazard. In the past, different authors proposed classification schemes for distinguishing different mechanisms for fluid-induced seismicity generation (see, e.g. McGarr 2000). For ex...

In Italy, the discussion about anthropogenic seismicity started after the deadly M6 Emilia earthquakes in 2012. Occurring these events in an area of gas and oil production, the question raised, whether stress perturbations induced by the exploitation may have triggered these events. In 2014, the Government published monitoring guidelines (ILG) desc...

In Italy, the discussion about anthropogenic seismicity started after the deadly M6 Emilia earthquakes in 2012. Occurring these events in an area of gas and oil production, the question raised, whether stress perturbations induced by the exploitation may have triggered these events. In 2014, the Government published monitoring guidelines (ILG) desc...

The Vrancea region is one of the few locations of deep seismicity in Europe. Seismic tomography has been able to map lithospheric downwelling, but has not been able yet to clearly discriminate between competing geodynamic interpretations of the geological and geophysical evidence available. We study the seismic structure of the Vrancea subduction z...

Up until now, Portugal lacked a countrywide shear velocity model sampling short length-scale crustal structure, which limits interpretations of seismicity and tectonics, and predictions of strong ground motion. In turn, such interpretations and predictions are important to help mitigate risk of destruction from future large on- and offshore earthqu...

Northern Italy is a diverse geological region, including the wide and thick Po Plain sedimentary basin, which is bounded by the Alps and the Apennines. The seismically slow shallow structure of the Po Plain is difficult to retrieve with classical seismic measurements such as surface wave dispersion, yet the detailed structure of the region greatly...

Seismology is learning to use the full-length records of seismic events and background ambient noise to go beyond still-life snapshots of the interior of the Earth, and look into time-dependent changes of its properties. Data availability has grown dramatically with the expansion of seismographic networks and data centers, and new efforts now targe...

The laterally heterogeneous structure of the Antarctic continental lithosphere affects the response to the time-varying cryospheric loads at the surface, and mantle dynamics at depth. So far, knowledge of these complex interactions has been quite sketchy: glacial isostatic adjustment is generally studied by means of layered rheological models, intr...

We measure ellipticity of teleseismic Rayleigh waves at 95 seismic stations in Northern Italy, for wave period between 10 and 110 s, using an automatic technique and a large volume of high-quality seismic recordings from over 500 global earthquakes that occurred in 2008– 2014. Northern Italy includes a wide range of crustal structures, from the wid...

The amplitude ratio between horizontal and vertical components of Rayleigh waves (also known as ellipticity) is in principle uniquely sensitive to local earth structure beneath each recording station. Rayleigh wave ellipticity is mostly influenced by the shallowest layers, so it can be effectively used to infer the structure of the uppermost crust,...

We derive the 3-D crustal structure (S wave velocity) underneath Italy and the Alpine region, expanding and exploiting the database of ambient noise Rayleigh-wave phase- and group-velocity of Verbeke et al. (2012). We first complement the database of Verbeke et al. (2012) with a dense set of new ambient-noise-based phase-velocity observations. We n...

Seismic noise in the period band 3-10 s is known as secondary microseism and it is generated at the ocean surface by the interaction of ocean gravity waves coming from nearly opposite directions. In this paper, we investigate the seismic content of the wavefield generated by a source at the ocean surface and three of the major wavefield shaping fac...

We built a 3D seismic model of the Po Plain and neighboring regions of northern Italy, covering altogether an area about 600 km by 300 km with an approximately 1 km spaced grid. We started by collecting an extensive and diverse set of geological and geophysical data, including seismic reflection and refraction profiles, borehole logs, and available...

Surface-wave dispersion measurements based on seismic background signal (ambient noise) are a very effective means to image S-wave velocity at crustal and lithospheric depths. The goal of our study is to integrate new ambient noise data for central Europe with more traditional models of crustal heterogeneity and discontinuity depths. We find that t...

Since the early 20th century the two main towers of Bologna (Northern Italy), Asinelli and Garisenda, perhaps the main monumental landmark of the city, have been studied by researchers of the University of Bologna, in order to assess their structural safety (Cavani 1912). Following the two mainshocks of the seismic sequence of Emilia Romagna (North...

Following the two mainshocks of the seismic sequence of Emilia Romagna (Northern Italy) (May 20th and 29th, 2013, respectively M 5.9 and 5.8, about 50 km far from Bologna), from June to September 2012 six seismic stations have been installed inside the two principal medieval Towers of Bologna (Italy), Asinelli and Garisenda. Four and two seismic st...

Secondary microseismic noise is generated by the non-linear interaction between ocean waves at the ocean surface during storms. We present here the theory for computing the source site effect of noise body waves due to the bathymetry, by considering noise sources as point vertical forces at the ocean surface. We use ray theory to show that the site...

We present a 3-D P wave velocity model of the crust and shallowest mantle under the Italian region, that includes a revised Moho depth map, obtained by regional seismic travel time tomography. We invert 191,850 Pn and Pg wave arrival times from 6850 earthquakes that occurred within the region from 1988 to 2007, recorded by 264 permanent seismic sta...

Different tectonic units cover the continents: platform, orogens and depression structures. This structural variability is reflected both in thickness and physical properties of the crust. We present a new global Moho map for the continental crust, derived from geophysical data selected from the literature and regional crustal models. The Moho dept...

Different tectonic units cover the continents: platform, orogens and depression structures. This structural variability is reflected both in thickness and physical properties of the crust. We present a new global Moho map for the continental crust, derived from geophysical data selected from the literature and regional crustal models. The Moho dept...

Different tectonic units cover the Antarctic territory: platform, orogens and depression structures. This structural variability is reflected both in thickness and physical properties of the crust. We present a new Moho map for the Antarctica, derived from geophysical data selected from the literature. The model covers the whole Antarctic region, f...

This Google-Earth kml file contains the event locations for the 121 icequake events discussed in the Danesi et al EPSL paper. The locations were derived by double-difference relocation, using the hypodd algorithm.

Secondary microseisms recorded by seismic stations are generated in the ocean by the interaction of ocean gravity waves. We present here the theory for modelling secondary microseism noise by normal mode summation. We show that the noise sources can be modelled by vertical forces and how to derive them from a realistic ocean wave model. We then sho...

Different tectonic units cover the Antarctic territory: platform, orogens and depression structures. This structural variability is reflected both in thickness and physical properties of the crust. This continent has high interest for Earth sciences, because of its origin as the core of the Gondwana supercontinent, and because of a number of presen...

A new Moho depth map for the Antarctic continent has been recently assembled (ANTMoho), merging information retrieved from geophysical and geological studies selected from the literature. A large volume of old and new data have been analyzed: from active seismic prospection,including DSS profiles acquired by Soviet Union field experiments, to recen...

Alle ore 02.03 UTC di domenica 20 maggio 2012, la Rete Sismica Nazionale (RSN [Amato and Mele, 2008; Delladio, 2011]) dell’Istituto Nazionale di Geofisica e Vulcanologia (INGV) ha registrato un evento simico di magnitudo locale 5.9 che è stato avvertito in gran parte dell’Italia centro-settentrionale; l’evento è stato localizzato sotto la valle del...

Recent developments in algorithms and computer architecture make neural networks a useful tool in designing pattern recognition systems. We show how a simple multilayer perceptron with 23 neurons can be trained easily and used to classify seismic signals. Applied to broadband seismic signal, the perceptron permitted the recognition of different typ...

On May 20th 2012 (Sunday) an earthquake (ML 5.9) hit Northern Italy at 02:03 UTC,. The National Seismic Network [Amato and Mele, 2008; Delladio, 2011] of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) located the hypocenter below the Po Valley in the Emilia region (44.89° N, 11.23° E, 6.3 km depth). Just after the mainshock, the INGV str...

p>Rapid-response seismic networks are an important element in the response to seismic crises. They temporarily improve the detection performance of permanent monitoring systems during seismic sequences. The improvement in earthquake detection and location capabilities can be important for decision makers to assess the current situation, and can pro...