luca baradello - Academia.edu (original) (raw)

Papers by luca baradello

Lithological characterization of the seafloor is key information for offshore engineering, especi... more Lithological characterization of the seafloor is key information for offshore engineering, especially when it comes to pier and platform design. Drilling and coring can be used for local sampling, but continuous profiles or even areal coverage are far preferable. High-resolution seismic profiles are successfully used when ports are not too busy, but otherwise single-channel systems must be used. We show in this paper that even these simpler systems can be used to estimate parameters such as the acoustic impedance of shallow sediments directly beneath the seafloor. We exploit the amplitude decay of the multiple reflections between the seafloor and the surface, which does not depend on the source energy. If the offset between source and receiver is not too small, we can estimate the shallow P velocity and, via the acoustic impedance, also the rock density.

Summary In this work we present an application of cluster analysis on seismic and electrical data... more Summary In this work we present an application of cluster analysis on seismic and electrical data with the aim to identify the important structures present in the investigated area. To define the clusters we use the cross-plot representation of sesmic velocity vs. resistivity, obtained from the travel time tomography and the Electrical Resistivity Tomography (ERT) respectively. The seismic and electrical data were acquired in four 2D lines. The studied area belongs to the Quaternary front of the eastern Southern Alps in Northeastern Italy, characterized by the presence of a tectonic actvity which caused deformation of the Upper Pleistocene — Holocene deposits. The applied method allowed us to separate the zones with similar seismic and electrical properties to better distinguish the different structures buried in the investigated area. The results point out a discontinuity in the shallow structures, which testifies the presence of an important fault, assumed to exist in this area.

Marine Geophysical Research, 2021

Chirp technology is an acoustic tool for imaging the shallow seabed with a high resolution, used ... more Chirp technology is an acoustic tool for imaging the shallow seabed with a high resolution, used for investigations of modern to Quaternary sedimentary structures and processes and more applied goals, such as hazard surveys for drilling, archeology, geology or engineering fields. In this paper, we present new methods that improve such imaging. During the standard acquisition, the Chirp waveforms are converted into analytic signals and only their envelope is preserved and interpreted, because the highly oscillating signal is otherwise difficult to be identified visually. Doing so, however, the phase information is lost, and the final processing is limited mainly to simple time-varying gain recovery or filtering. We present a work flow including a derivative step to transform the enveloped signal into a seismic-like waveform. In this way, we can apply processing tools as FX deconvolution and migration to improve the signal/noise ratio and reduce diffractions. This method allows reviving standard and legacy Chirp data where the full-waveform information is missing.

Geosciences, 2022

The increasing demand for freshwater requires the identification of additional and less-conventio... more The increasing demand for freshwater requires the identification of additional and less-conventional water resources. Amongst these, offshore freshwater systems have been investigated in different parts of the world to provide new opportunities to face increasing water requests. Here we focus on the north-eastern Adriatic Sea, where offshore aquifers could be present as a continuation of onshore ones. Geophysical data, in particular offshore seismic data, and onshore and offshore well data, are interpreted and integrated to characterise the hydrogeological setting via the interpretation of seismo-stratigraphic sequences. We focus our attention on two areas located in the proximity of the Tagliamento and Isonzo deltas. Well and seismic data indicate that the Quaternary sediments, that extend from onshore to offshore areas, are the most promising from an offshore freshwater resources point of view, while the several kilometres thick pre-Quaternary carbonate and terrigenous sequences l...

All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.

Marine Geophysical Research, 2014

ABSTRACT Chirp sonar systems can be used to obtain high resolution seismic reflection images of t... more ABSTRACT Chirp sonar systems can be used to obtain high resolution seismic reflection images of the sub-seafloor during marine surveys. The exact knowledge of the Chirp signature allows the use of deterministic algorithms to process the data, similarly to that applied to Vibroseis data on land. Here, it is described an innovative processing sequence to be applied to uncorrelated Chirp data, which can improve vertical and lateral resolution compared to conventional methods. It includes application of a Wiener filter to transform a frequency-modulated sweep into a minimum-phase pulse sequence. In this way, the data become causal and can undergo predictive deconvolution to reduce ringing and enhance vertical resolution. Afterwards, FX-deconvolution and Stolt migration can be applied to obtain an improved imaging of the subsurface. The result of this procedure is a seismic reflection image with higher resolution than traditional ones, which are normally represented using the envelope function of the signal. This technique can be particularly useful for engineering-geotechnical surveys and archaeological investigations that require a fine detail imaging of the uppermost meters of the sub-seafloor.

The University of Modena and Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS)... more The University of Modena and Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) collaborated to acquire two geophysical data set in two areas located near Sassuolo (Modena; Northen Appenines). The first area is characterized by fossil fluid expulsion structures forming in the Upper Miocene, while the second one is actually interested by expulsion of mud and free gas. We used seismic 3D surveys to reconstruct in detail the shallow structures in both areas. Ground Penetrating Radar (GPR) and geo-electrical survey are used only in the second area to better characterize the first meters. The fossil structures located in the first area (Sasso Strega) have a horizontal dimension of about 10 meters, and a vertical extension of few ten. To investigate the presence of these buried structures a 3D seismic acquisition was performed, in which additional shots are located across the investigated area by using the natural topography to have the same effect of a deep source. In this way, the structures are lightened directly from the bottom. The source was the mini-bang and the receivers are vertical geophones (10 Hz). The receiver inline and cross-line intervals were 5 m, while the source interval was equal to 5 m (for inline shots) and 10 m (for cross-line shots). After the processing of the data to increase the signal/noise ratio, the tomographic inversion of the first breaks was applied to determine the geometry and the compressional velocity of buried structures. In the second site (near Nirano), a 3D seismic acquisition was acquired using three component geophones. In this case, the source was a Vibroseis source, that generates both compressional and shear waves. So, the acquisition allowed us to obtain information about both compressional and shear velocity fields by using the inversion tomography of the first arrivals. Of course, the comparison between the two fields is an useful tool to investigate the fluid presence in the investigated area. In fact, it is well known that the compressional velocities are influenced by both matrix and fluid, while the shear velocities detect only the matrix change.In this site we also collected geoelectrical and GPR data to recostruct the shallow features of the subsoil. In particular the geoelectrical data are inverted using tomographic approach to obtain the resistivity and chargeability models.We present the preliminary results of the collected data in the two areas

Italian Journal of Geosciences, 2020

Following the large 1982 Ancona landslide, which affected a densely populated district with many ... more Following the large 1982 Ancona landslide, which affected a densely populated district with many man-made infrastructures, a big effort was made by the scientific community to study the area and a great amount of geophysical and geotechnical data were acquired. The region is part of the external domain of Central Apennine resulted by Neogene compressive deformations. The tectonic processes have resulted in instabilities along the entire central Adriatic coasts of Italy, marked today by large-scale gravitational phenomena. An early Pleistocene regional uplift formed a slope subject to glacioeustatic sea-level oscillations, with erosion and water infiltration, favouring instability and movements under the action of gravitational driving forces. Sliding surface formation and roto-translational displacements have occurred until the recent reactivations of earth-flows and chaotic mounds at the slope break in correspondence with the formation of the Peri-Adriatic basin. In this paper, we present images of seismic sections obtained from the processing of two sea-land reflection profiles and offshore very high-resolution prospecting. Our paper intends to reinforce the importance of a multi-disciplinary approach integrating geophysical data to geological, morphological and engineering methods. The seismic survey of the two sea-land sections considered a joint land–sea acquisition to image the subsurface in the transitional zone. Composite sections were obtained from the processing of differently recorded sub-datasets, which depended on the type of land and marine sources and sensors in combination with the unique frequency content, source strength and noise, such as the propagation of surface-waves or air-gun bubbles. The properly acquired and processed data yielded post-stack migrated depth converted seismic sections, reflecting interfaces down to approximately 1400 m depth, where the top of Messinian evaporites has been encountered. The final sections reveal the deep structural settings and the importance of the still active anti-Apennine transfer faults.The offshore Boomer high-resolution profiles show only the near sea-bottom sequences. These fluvio-deltaic Plio-Quaternary deposits represent the final filling phase of the foreland basins, exposed to sub-aerial erosion during the last glacial period and to submersion during the subsequent sea-level rise of approximately 120 m.The final sections reveal the deep structural settings and the importance of the still active anti-Apennine transfer faults.

Geosciences

Conventional multichannel surveys provide good images in 2D and 3D of the Earth in depth, which a... more Conventional multichannel surveys provide good images in 2D and 3D of the Earth in depth, which are successfully used for the oil and gas industries. However, their cost and environmental impact make them rarely affordable for engineering applications, especially for offshore infrastructures. In this case, monochannel systems, such as Boomers, having cables that are a few-meters long, provide time-domain images that are useful but miss relevant lithological information for engineers, such as the P-wave velocity of shallow layers. In this paper, we present a tomographic approach that exploits multiple reflections, in addition to primaries and direct arrivals, which work for monochannel surveys with a short offset. It can detect lateral variations of velocity and thickness of the first layer under the sea floor. Two complementary algorithms are compared: a pure tomographic inversion, and a tuning exploiting the classical Dix formula; the first one is more precise, while the second is ...

Applied Sciences, 2022

The shallow P velocity provides relevant information for offshore engineers, in planning pipeline... more The shallow P velocity provides relevant information for offshore engineers, in planning pipelines, piers, and platforms. Standard multichannel surveys trailing long cables provide good estimates but may require stopping other ongoing operations or may affect the environment. Monochannel surveys by Boomer systems involve a very short cable, so those drawbacks are minimized; however, this comes at the cost of loss of information for estimating the P velocity of shallow layers. In this paper, we present a new method exploiting multiple reflections for characterizing the seafloor. After validation of the algorithm by a synthetic example, we tested this approach in a marine survey acquired by a Boomer system at the Gulf of Trieste (Italy).

Tectonophysics, 2021

Abstract We carried out new geological, morphotectonic, geophysical and paleoseismological invest... more Abstract We carried out new geological, morphotectonic, geophysical and paleoseismological investigations on the Meduno Thrust that belongs to the Pliocene-Quaternary front of the eastern Southern Alps in Friuli (NE Italy). The study area is located in the Carnic Prealps, where a series of alluvial terraces, linked to both climatic and tectonic pulses characterises the lower reach of the Meduna Valley. In correspondence of the oblique ramp of the Meduno Thrust, the Late Pleistocene Rivalunga terrace shows a set of scarps perpendicular to the Meduno valley, often modified by human activity. In order to reconstruct the tectonic setting of the area and identify the location for digging paleoseismological trenches, integrated geophysical investigations including electrical resistivity tomography, seismic refraction and reflection, ground penetrating radar and surface wave analyses (HVSR, ReMi and MASW), were carried out across the scarps of the Rivalunga terrace. Geophysical surveys pinpointed that in correspondence of the oblique ramp, stress is accommodated by a transpressive thrust system involving all the seismo-stratigraphic horizons apart from the ploughed soil. Trenching illustrated the Meduno Thrust movements during Late Pleistocene-Holocene. Trenches exhibited both shear planes and extrados fracturing, showing deformed alluvial and colluvial units. 14C datings of the colluvial units show that the most recent fault movements occurred after 1360 CE and 1670 CE. The age of the deformed stratigraphic units compared with the earthquakes listed in current catalogues, suggests that the 1776 earthquake (Mw 5.8, Io = 8–9 MCS) could represent the last seismic event linked to the Meduno thrust activity. This study provided new quantitative constraints improving seismic hazard assessment for Carnic prealpine area.

Engineering Geology, 2020

Abstract Seismic microzonation represents a basic tool for prevention activity planning and land ... more Abstract Seismic microzonation represents a basic tool for prevention activity planning and land management. An extensive and detailed microzonation study was performed with reference to the territory of the Municipality of Cavezzo, damaged during the seismic sequence hitting Emilia-Romagna Region, Northern Italy, in 2012. In this paper, we discuss the work carried out to characterize the spatial variability of ground motion amplification due to local soil conditions in the municipality area. An inter- and multi-disciplinary approach is presented, involving geotechnical engineers, geophysicists, geologists and seismologists from different institutions, to thoroughly characterize the territory using complementary techniques with different level of resolution and confidence. A considerable amount of geomorphological, geological, hydrogeological, seismological, geotechnical and geophysical investigations was collected and processed for the purpose. A GIS-based (Geographic Information System) platform was initially setup to manage the gathered data, which now includes the results of about 1000 geotechnical and geophysical tests. Such an extended dataset was then used as a primary constraint for the creation of a comprehensive pseudo-3D geotechnical and seismo-stratigraphic model of the territory, consisting of a dense grid of one-dimensional vertical profiles to depict the variability of the soil properties over the area. The model was finally used as input for linear-equivalent ground response analysis. For the calculation of the amplification factors, special emphasis was given to the treatment and propagation of the uncertainties of the model parameters, whose different realizations have been accounted through a logic tree approach.

Scientific Reports, 2020

Perito Moreno is the most famous calving glacier of the South Patagonia Icefield, the largest tem... more Perito Moreno is the most famous calving glacier of the South Patagonia Icefield, the largest temperate glacier system of the Southern Hemisphere. Unlike most of the glaciers in the region that have strongly retreated in recent decades, the position of Perito Moreno glacier front remained relatively unchanged in the last century. However, earliest photographic documents show that, at the end of the nineteenth century, the front was ca. 800 m behind the current position. There is no reliable information about the positions of the Perito Moreno front in earlier times. Here we show evidence of two subaqueous moraine systems both in the Canal de Los Témpanos and in the Brazo Rico, the two arms of Lago Argentino along which Perito Moreno glacier has flowed over time. These moraines, identified for the first time in the Canal de Los Témpanos from bathymetric and high-resolution seismic profiles, mark the position of the largest glacier advance, tentatively correlated with the moraines of ...

Near Surface 2005 - 11th European Meeting of Environmental and Engineering Geophysics, 2005

ABSTRACT

EAGE Research Workshop - Advances in Seismic Acquisition Technology, 2004

A02 NEW APPROACH ON SEISMIC SURVEY ON SUBGLACIAL LAKES Abstract 1 The main obiective of ELSA proj... more A02 NEW APPROACH ON SEISMIC SURVEY ON SUBGLACIAL LAKES Abstract 1 The main obiective of ELSA project in December 2003 was to verify the applicability of the reflection sismic method for the definition of subglacial structures in the antarctic icecap.. The purposes of the survey were to verify: the correct operation of the recording system the acquisiton parameters p based on the theoretical models and the quality of the obtainable data by the use of different types of sources and acquisition geometries. Introduction The subglacial lakes are water bodies enclosed between the base of the glacial column and the bedrock.