Umberta Tinivella - Profile on Academia.edu (original) (raw)
Papers by Umberta Tinivella
Soil characterization and seismic hazard maps for the Friuli Venezia Giulia region (NE Italy)
ABSTRACT Seismic hazard maps that account for site amplification (soil seismic hazard maps) are v... more ABSTRACT Seismic hazard maps that account for site amplification (soil seismic hazard maps) are very useful because they represent the expected ground motion at the Earth's surface, but need much more information and elaboration than the usual rock hazard maps. The regional soil hazard map has been developed for the Friuli Venezia Giulia region, in northeastern Italy, by considering the most updated approach. In fact, the structure of the seismic hazard analysis presented here is based on the logic tree approach to achieve a robust statistical computation taking into account, in addition to the aleatory variability, also the epistemic uncertainties. The logic tree adopted for rock and soft soil conditions consists of 54 branches: three seismogenic zonations, representing various levels of our seismotectonic knowledge, three methods for the seismicity rate computation, three statistical approaches for the maximum magnitude estimation, and two PGA attenuation models of different spatial relevance (European and Italian). An additional regional attenuation model was considered only for stiff soil conditions, increasing the number of branches of the logic tree to 81. A consolidated expeditive procedure, widely adopted in the United States, has been used to compute the soil ground motion, properly modified on the basis of specific calibrations based on the local geological conditions and the results of geotechnical soundings. The final result of this study is represented by the map of the expected ground motion in the Friuli Venezia Giulia region, computed considering the different litho-stratigraphic and morphological conditions existing in the area. This map clearly shows the contribution given by the soft sediments along the Alpine valleys and by the steep formation of the moraine amphitheatre in central Friuli. A comparison of these new results with those obtained by applying the amplification factors provided by the most popular seismic codes points out that the actual ground shaking could be notably larger than that obtained by the application of the seismic codes, suggesting a possible future implementation in the regional building code, so far not taken into account.
Structures in the continental crust and geothermal resources
Compressional velocity structure and Poisson's ratio in marine sediments with gas hydrate and free gas by inversion of reflected and refracted seismic data (South Shetland Islands, Antarctica)
Marine Geology, 2000
A Bottom Simulating Reflector (BSR) on the South Shetland Margin (Antarctic Peninsula) was survey... more A Bottom Simulating Reflector (BSR) on the South Shetland Margin (Antarctic Peninsula) was surveyed, within the Progetto Nazionale di Ricerche in Antartide (PNRA). High resolution multichannel (MCS) reflection profiles were acquired, and a three-component Ocean Bottom Seismograph (OBS) was deployed where the BSR was particularly strong.The compressional velocity field associated to the BSR was determined by the inversion of travel
Coastal areas are generally characterized by human manufacturing; thus, seismic data analysis is ... more Coastal areas are generally characterized by human manufacturing; thus, seismic data analysis is necessary to characterize the properties of the subsoil, the main purpose of which is to clarify risk situations. In the case of very shallow water environments, seismic multiple attenuation becomes a challenge when the reflection of the seafloor is post-critical, so it is not recorded because of the acquisition parameters. We propose an approach to attenuate the multiples by using wave equation datuming that does not require the detection of seafloor reflection and avoids the seafloor reflection prediction and related approximations in the post-critical conditions. Moreover, this approach allows for the enhancement of higher frequencies, and, consequently, an increase in resolution, demonstrating that it is a powerful tool to attenuate multiples and reverberations, especially where other approaches are found to be inefficient. An example of the application of seismic data acquired in the continental shelf of South Chile is reported.
In this study one seismic section offshore Chiloé Island was analyzed to better define the seismi... more In this study one seismic section offshore Chiloé Island was analyzed to better define the seismic character of the hydrate-bearing sediments. The velocity analysis was used to estimate the gas-phase concentration and relate it to the geological features. The velocity model allowed us to recognize two important layers that characterize hydrate-and free gas-bearing sediments above and below the BSR respectively: one located above the BSR, characterized by high velocity (1,800-2,200 m/s) and a second one, below the BSR, characterized by low velocity (1,600-1,700 m/s). A weak ref lector at about 100 m below the BSR marks the base of the second layer. AVO analysis and offset stack sections confirming that the reflector interpreted as BGR is related to free gas presence in the pore space. The velocity field is affected by lateral variation, showing maximum (above the BSR) and minimum (below the BSR) values in the sector. Here, the highest gas hydrate and free gas concentrations were calculated, obtaining 9.5% and 0.5% of total volume respectively. A variable BSR depth (from 300 to 600 mbsf) can be justified supposing a variable geothermal gradient (from 25 to 45 °C/km). RESUMEN. Estimación de hidratos de metano y gas libre mediante análisis sísmico frente a Chiloé (Chile). Este estudio analiza una sección sísmica marina frente a Chiloé, con el objeto de definir a través de las propiedades sísmicas las características de los sedimentos que contienen hidratos de metano. Mediante el análisis de la velocidad sísmica, es estimada la concentración de la fase-gas y su relación con estructuras geológicas. El modelo de velocidad permite reconocer dos capas importantes, una sobre el BSR de alta velocidad (1,800-2,200 m/s) asociada a hidrato y otra por debajo del BSR de baja velocidad (1,600-1,700 m/s) relacionada con la fase-gas libre. Un débil ref lector, ubicado aproximadamente a 100 m por debajo del BSR, marca la base de la segunda capa. Un análisis de AVO y secciones apiladas por offset permiten confirmar que este corresponde al BGR y que estaría relacionado con la presencia de gas libre. La velocidad sísmica varía lateralmente, alcanzando un valor máximo (sobre el BSR) y un mínimo (bajo el BSR) en el área. Las más altas concentraciones de hidrato y gas libre son alcanzadas en esta área (9,5% y 0,5% del volumen total respectivamente). El aumento en la profundidad del BSR (desde 300 a 600 mbsf) es justificado suponiendo un gradiente geotérmico variable (desde 25 a 45 °C/km).
Tectonophysics, 2010
A crustal reflection seismic profile, more than 100 km long, was recorded across central Sicily, ... more A crustal reflection seismic profile, more than 100 km long, was recorded across central Sicily, from the Tyrrhenian shore to the Sicily Channel, to understand the deep structures and the collision mechanisms between Europe and Africa and the subsequent geodynamic evolution. The profile was acquired using explosive sources and 240 active channels recorded by a Sercel 408-XL, 24 bits A/D converter, with a 12 km spread and a 24-fold coverage. The data were processed following a non-conventional procedure in order to preserve the relative amplitudes of the reflections and to better investigate the Sicily deep structures down to the Moho. The main highlighted structures are the dramatic flexure of the Iblean crust, the huge, deeper than expected, trough of Caltanissetta consisting of deep seated thrusts and nappes, and the imbricate thrust system of rigid bodies characterizing the northern Maghrebian chain. We designed an ad hoc acquisition and processing in order to highlight these main geological features in the seismic stacked section. Moreover, the deepest parts of the Caltanissetta trough are imaged for the first time, and its bottom is now fixed at more than 7 s TWT. The giant crustal wedge flexuring the Iblean foreland and the Moho geometries are examinated.
Seismic reflection tomography and theoretical velocity relations in porous media for quantitative estimates of free gas and gas hydrates
Bollettino Di Geofisica Teorica Ed Applicata, Apr 30, 1999
Highlighting the crustal structure of the Tuscan Geothermal Province
Bollettino di Geofisica Teorica ed Applicata
Seismic reflection tomography and theoretical velocity relations in porous media for quantitative estimates of free gas and gas hydrates
SEG Technical Program Expanded Abstracts 2010, 2010
Glacial History of the Antarctic Peninsula from Pacific Margin Sediments
Proceedings of the Ocean Drilling Program, 2001
For more information about how to use this volume, where to download Adobe Reader, or comments, s... more For more information about how to use this volume, where to download Adobe Reader, or comments, see the User Guide. ... Volume and chapter citations have been updated since original publication to include a Digital Object Identifier (DOI) to facilitate online access to scholarly and professional content (see "Citations Related to ODP Legs" for updated citations). ... This volume contains ASCII versions of selected data tables. ... Table T1. Hole 1098A digital image color data. Table T2. Hole 1098B digital image color data. Table T3. Hole 1098C digital image ...
Random pseudobinary ionic alloys: lattice energy and structural properties
Journal of Physics: Condensed Matter, 1997
ABSTRACT Experimental data suggest that in ionic solid solutions the bond-length mismatch is part... more ABSTRACT Experimental data suggest that in ionic solid solutions the bond-length mismatch is partially accommodated by microscopic lattice distortions. In this paper we study the structural properties of ionic alloys using a generalized Born - Mayer energy model accounting for the possibility of atomic-scale relaxations. Cubic supercells are used to simulate the real random alloys, providing statistical information about the atomic distribution and interatomic distances. The good agreement with the available experimental data and with the results of ab initio pseudopotential calculations performed for comparison for some selected systems indicate the validity of the model here employed. We also discuss the applicability to ionic alloys of the special quasi-random structures originally proposed for semiconducting alloys.
Southern Chile Accretionary Wedge: Correlation between the Proto-Deformation Zone and Overpressured Fluids Evidenced by AVO Analysis
7. Climate Variability of the Holocene, Site 1098, Palmer Deep, Antarctica (PDF)
This volume is available in HTML and Adobe Acrobat PDF formats. The HTML version is intended for ... more This volume is available in HTML and Adobe Acrobat PDF formats. The HTML version is intended for online viewing only (click on titles). Use the PDF file to generate a printed version or to view higher resolution graphics (click on "PDF" at the end of the titles). ... For more information about how to use this volume, where to download Adobe Acrobat Reader, or comments, see the User Guide. ... Chapters are listed in thematic order. To view chapters by numerical (acceptance) order see Chapters List. ... This volume contains ASCII versions of selected data tables.
Journal of Applied Geophysics, 2007
An integrated geophysical and geological study of small mud volcanoes occurring along the externa... more An integrated geophysical and geological study of small mud volcanoes occurring along the external compressive margin of the chain in the northern Apennines was carried out in order to investigate the fluid pathways and the mud reservoir. Results obtained by tomographic inversion of first arrivals of 3D seismic data, and models obtained by 2D geo-electrical data, allow determination of the geometry of the buried shallow structures, and the details of the fluid seepage down to 50 m below the mud volcano surface.
Two seismic sections offshore Arauco and Coyhaique, Chile, have been analysed to better define th... more Two seismic sections offshore Arauco and Coyhaique, Chile, have been analysed to better define the seismic character of hydrate-bearing sediments. The velocity analysis was used to estimate the gas-phase concentration, which can serve to correlate hydrate presence to the geological features. The velocity model allowed us to recognise the hydrate layer above the bottom simulating reflector (BSR), and the free gas layer below it. The velocity field is affected by strong lateral variation, showing maximum (above the BSR) and minimum (below the BSR) values in the southern sector. Here, highest gas hydrate and free gas concentrations were calculated (15% and 2.7% of total volume respectively). The estimated geothermal gradient ranges from 35 to 95°C/km. In the northern sector, the highest gas hydrate and free gas concentrations are 15% and 0.2% of total volume respectively, and the geothermal gradient is uniform and equal to about 30°C/km.
An application to integrate bathymetric and other dataset to study gas hydrates reservoir
Soil characterization and seismic hazard maps for the Friuli Venezia Giulia region (NE Italy)
ABSTRACT Seismic hazard maps that account for site amplification (soil seismic hazard maps) are v... more ABSTRACT Seismic hazard maps that account for site amplification (soil seismic hazard maps) are very useful because they represent the expected ground motion at the Earth's surface, but need much more information and elaboration than the usual rock hazard maps. The regional soil hazard map has been developed for the Friuli Venezia Giulia region, in northeastern Italy, by considering the most updated approach. In fact, the structure of the seismic hazard analysis presented here is based on the logic tree approach to achieve a robust statistical computation taking into account, in addition to the aleatory variability, also the epistemic uncertainties. The logic tree adopted for rock and soft soil conditions consists of 54 branches: three seismogenic zonations, representing various levels of our seismotectonic knowledge, three methods for the seismicity rate computation, three statistical approaches for the maximum magnitude estimation, and two PGA attenuation models of different spatial relevance (European and Italian). An additional regional attenuation model was considered only for stiff soil conditions, increasing the number of branches of the logic tree to 81. A consolidated expeditive procedure, widely adopted in the United States, has been used to compute the soil ground motion, properly modified on the basis of specific calibrations based on the local geological conditions and the results of geotechnical soundings. The final result of this study is represented by the map of the expected ground motion in the Friuli Venezia Giulia region, computed considering the different litho-stratigraphic and morphological conditions existing in the area. This map clearly shows the contribution given by the soft sediments along the Alpine valleys and by the steep formation of the moraine amphitheatre in central Friuli. A comparison of these new results with those obtained by applying the amplification factors provided by the most popular seismic codes points out that the actual ground shaking could be notably larger than that obtained by the application of the seismic codes, suggesting a possible future implementation in the regional building code, so far not taken into account.
Structures in the continental crust and geothermal resources
Compressional velocity structure and Poisson's ratio in marine sediments with gas hydrate and free gas by inversion of reflected and refracted seismic data (South Shetland Islands, Antarctica)
Marine Geology, 2000
A Bottom Simulating Reflector (BSR) on the South Shetland Margin (Antarctic Peninsula) was survey... more A Bottom Simulating Reflector (BSR) on the South Shetland Margin (Antarctic Peninsula) was surveyed, within the Progetto Nazionale di Ricerche in Antartide (PNRA). High resolution multichannel (MCS) reflection profiles were acquired, and a three-component Ocean Bottom Seismograph (OBS) was deployed where the BSR was particularly strong.The compressional velocity field associated to the BSR was determined by the inversion of travel
Coastal areas are generally characterized by human manufacturing; thus, seismic data analysis is ... more Coastal areas are generally characterized by human manufacturing; thus, seismic data analysis is necessary to characterize the properties of the subsoil, the main purpose of which is to clarify risk situations. In the case of very shallow water environments, seismic multiple attenuation becomes a challenge when the reflection of the seafloor is post-critical, so it is not recorded because of the acquisition parameters. We propose an approach to attenuate the multiples by using wave equation datuming that does not require the detection of seafloor reflection and avoids the seafloor reflection prediction and related approximations in the post-critical conditions. Moreover, this approach allows for the enhancement of higher frequencies, and, consequently, an increase in resolution, demonstrating that it is a powerful tool to attenuate multiples and reverberations, especially where other approaches are found to be inefficient. An example of the application of seismic data acquired in the continental shelf of South Chile is reported.
In this study one seismic section offshore Chiloé Island was analyzed to better define the seismi... more In this study one seismic section offshore Chiloé Island was analyzed to better define the seismic character of the hydrate-bearing sediments. The velocity analysis was used to estimate the gas-phase concentration and relate it to the geological features. The velocity model allowed us to recognize two important layers that characterize hydrate-and free gas-bearing sediments above and below the BSR respectively: one located above the BSR, characterized by high velocity (1,800-2,200 m/s) and a second one, below the BSR, characterized by low velocity (1,600-1,700 m/s). A weak ref lector at about 100 m below the BSR marks the base of the second layer. AVO analysis and offset stack sections confirming that the reflector interpreted as BGR is related to free gas presence in the pore space. The velocity field is affected by lateral variation, showing maximum (above the BSR) and minimum (below the BSR) values in the sector. Here, the highest gas hydrate and free gas concentrations were calculated, obtaining 9.5% and 0.5% of total volume respectively. A variable BSR depth (from 300 to 600 mbsf) can be justified supposing a variable geothermal gradient (from 25 to 45 °C/km). RESUMEN. Estimación de hidratos de metano y gas libre mediante análisis sísmico frente a Chiloé (Chile). Este estudio analiza una sección sísmica marina frente a Chiloé, con el objeto de definir a través de las propiedades sísmicas las características de los sedimentos que contienen hidratos de metano. Mediante el análisis de la velocidad sísmica, es estimada la concentración de la fase-gas y su relación con estructuras geológicas. El modelo de velocidad permite reconocer dos capas importantes, una sobre el BSR de alta velocidad (1,800-2,200 m/s) asociada a hidrato y otra por debajo del BSR de baja velocidad (1,600-1,700 m/s) relacionada con la fase-gas libre. Un débil ref lector, ubicado aproximadamente a 100 m por debajo del BSR, marca la base de la segunda capa. Un análisis de AVO y secciones apiladas por offset permiten confirmar que este corresponde al BGR y que estaría relacionado con la presencia de gas libre. La velocidad sísmica varía lateralmente, alcanzando un valor máximo (sobre el BSR) y un mínimo (bajo el BSR) en el área. Las más altas concentraciones de hidrato y gas libre son alcanzadas en esta área (9,5% y 0,5% del volumen total respectivamente). El aumento en la profundidad del BSR (desde 300 a 600 mbsf) es justificado suponiendo un gradiente geotérmico variable (desde 25 a 45 °C/km).
Tectonophysics, 2010
A crustal reflection seismic profile, more than 100 km long, was recorded across central Sicily, ... more A crustal reflection seismic profile, more than 100 km long, was recorded across central Sicily, from the Tyrrhenian shore to the Sicily Channel, to understand the deep structures and the collision mechanisms between Europe and Africa and the subsequent geodynamic evolution. The profile was acquired using explosive sources and 240 active channels recorded by a Sercel 408-XL, 24 bits A/D converter, with a 12 km spread and a 24-fold coverage. The data were processed following a non-conventional procedure in order to preserve the relative amplitudes of the reflections and to better investigate the Sicily deep structures down to the Moho. The main highlighted structures are the dramatic flexure of the Iblean crust, the huge, deeper than expected, trough of Caltanissetta consisting of deep seated thrusts and nappes, and the imbricate thrust system of rigid bodies characterizing the northern Maghrebian chain. We designed an ad hoc acquisition and processing in order to highlight these main geological features in the seismic stacked section. Moreover, the deepest parts of the Caltanissetta trough are imaged for the first time, and its bottom is now fixed at more than 7 s TWT. The giant crustal wedge flexuring the Iblean foreland and the Moho geometries are examinated.
Seismic reflection tomography and theoretical velocity relations in porous media for quantitative estimates of free gas and gas hydrates
Bollettino Di Geofisica Teorica Ed Applicata, Apr 30, 1999
Highlighting the crustal structure of the Tuscan Geothermal Province
Bollettino di Geofisica Teorica ed Applicata
Seismic reflection tomography and theoretical velocity relations in porous media for quantitative estimates of free gas and gas hydrates
SEG Technical Program Expanded Abstracts 2010, 2010
Glacial History of the Antarctic Peninsula from Pacific Margin Sediments
Proceedings of the Ocean Drilling Program, 2001
For more information about how to use this volume, where to download Adobe Reader, or comments, s... more For more information about how to use this volume, where to download Adobe Reader, or comments, see the User Guide. ... Volume and chapter citations have been updated since original publication to include a Digital Object Identifier (DOI) to facilitate online access to scholarly and professional content (see "Citations Related to ODP Legs" for updated citations). ... This volume contains ASCII versions of selected data tables. ... Table T1. Hole 1098A digital image color data. Table T2. Hole 1098B digital image color data. Table T3. Hole 1098C digital image ...
Random pseudobinary ionic alloys: lattice energy and structural properties
Journal of Physics: Condensed Matter, 1997
ABSTRACT Experimental data suggest that in ionic solid solutions the bond-length mismatch is part... more ABSTRACT Experimental data suggest that in ionic solid solutions the bond-length mismatch is partially accommodated by microscopic lattice distortions. In this paper we study the structural properties of ionic alloys using a generalized Born - Mayer energy model accounting for the possibility of atomic-scale relaxations. Cubic supercells are used to simulate the real random alloys, providing statistical information about the atomic distribution and interatomic distances. The good agreement with the available experimental data and with the results of ab initio pseudopotential calculations performed for comparison for some selected systems indicate the validity of the model here employed. We also discuss the applicability to ionic alloys of the special quasi-random structures originally proposed for semiconducting alloys.
Southern Chile Accretionary Wedge: Correlation between the Proto-Deformation Zone and Overpressured Fluids Evidenced by AVO Analysis
7. Climate Variability of the Holocene, Site 1098, Palmer Deep, Antarctica (PDF)
This volume is available in HTML and Adobe Acrobat PDF formats. The HTML version is intended for ... more This volume is available in HTML and Adobe Acrobat PDF formats. The HTML version is intended for online viewing only (click on titles). Use the PDF file to generate a printed version or to view higher resolution graphics (click on "PDF" at the end of the titles). ... For more information about how to use this volume, where to download Adobe Acrobat Reader, or comments, see the User Guide. ... Chapters are listed in thematic order. To view chapters by numerical (acceptance) order see Chapters List. ... This volume contains ASCII versions of selected data tables.
Journal of Applied Geophysics, 2007
An integrated geophysical and geological study of small mud volcanoes occurring along the externa... more An integrated geophysical and geological study of small mud volcanoes occurring along the external compressive margin of the chain in the northern Apennines was carried out in order to investigate the fluid pathways and the mud reservoir. Results obtained by tomographic inversion of first arrivals of 3D seismic data, and models obtained by 2D geo-electrical data, allow determination of the geometry of the buried shallow structures, and the details of the fluid seepage down to 50 m below the mud volcano surface.
Two seismic sections offshore Arauco and Coyhaique, Chile, have been analysed to better define th... more Two seismic sections offshore Arauco and Coyhaique, Chile, have been analysed to better define the seismic character of hydrate-bearing sediments. The velocity analysis was used to estimate the gas-phase concentration, which can serve to correlate hydrate presence to the geological features. The velocity model allowed us to recognise the hydrate layer above the bottom simulating reflector (BSR), and the free gas layer below it. The velocity field is affected by strong lateral variation, showing maximum (above the BSR) and minimum (below the BSR) values in the southern sector. Here, highest gas hydrate and free gas concentrations were calculated (15% and 2.7% of total volume respectively). The estimated geothermal gradient ranges from 35 to 95°C/km. In the northern sector, the highest gas hydrate and free gas concentrations are 15% and 0.2% of total volume respectively, and the geothermal gradient is uniform and equal to about 30°C/km.
An application to integrate bathymetric and other dataset to study gas hydrates reservoir