Mauro Antonio Di Vito, Ilaria Rucco, Sandro de Vita, Domenico Maria Doronzo, Marina Bisson, Mattia de' Michieli Vitturi, Mauro Rosi, Laura Sandri, Giovanni Zanchetta, Elena Zanella, Antonio Costa
Abstract. Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting the population and infrastructure. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma–Vesuvius and Campi Flegrei volcanoes, along with the Apennine reliefs, are mantled by pyroclastic deposits that can be easily remobilized, especially after intense and/or prolonged rainfall. This study focuses on the analysis of pyroclastic fall and flow deposits and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius in 472 CE (Pollena) and 1631. To begin with, historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database, which was integrated with several new pieces of data. In particular, stratigraphic, sedimentological (facies analysis and laboratory), and archeological analyses were carried out, in addition to rock magnetic investigations and impact parameter calculations. The new data are also referenced to the finding of ash beds in more distal areas, which were included in new isopach maps for the two sub-Plinian eruptions. The results show that for both eruptions the distribution of the primary deposits is wider than previously known. A consequence of these results is that a wider areal impact should be expected in terms of civil protection, as the sub-Plinian scenario is the reference one for a future large eruption of Vesuvius. Such a distribution of the pyroclastic deposits directly affects the one of the lahar deposits, also because a significant remobilization took place during and after the studied eruptions, which involved distal phreatomagmatic ash. From these integrated analyses, it was possible to constrain the timing of the deposition and the kind of deposits remobilized (pyroclastic fall vs. flow), and it was possible to calculate the velocities and dynamic pressures of the lahars and ultimately infer the lahar transport and emplacement mechanisms. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas even at distances of several to tens of kilometers from active volcanoes. This especially applies to large parts of the densely populated areas around Somma–Vesuvius up to the nearby Apennine valleys.
{"title":"Lahar events in the last 2000 years from Vesuvius eruptions – Part 1: Distribution and impact on densely inhabited territory estimated from field data analysis","authors":"Mauro Antonio Di Vito, Ilaria Rucco, Sandro de Vita, Domenico Maria Doronzo, Marina Bisson, Mattia de' Michieli Vitturi, Mauro Rosi, Laura Sandri, Giovanni Zanchetta, Elena Zanella, Antonio Costa","doi":"10.5194/se-15-405-2024","DOIUrl":"https://doi.org/10.5194/se-15-405-2024","url":null,"abstract":"Abstract. Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting the population and infrastructure. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma–Vesuvius and Campi Flegrei volcanoes, along with the Apennine reliefs, are mantled by pyroclastic deposits that can be easily remobilized, especially after intense and/or prolonged rainfall. This study focuses on the analysis of pyroclastic fall and flow deposits and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius in 472 CE (Pollena) and 1631. To begin with, historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database, which was integrated with several new pieces of data. In particular, stratigraphic, sedimentological (facies analysis and laboratory), and archeological analyses were carried out, in addition to rock magnetic investigations and impact parameter calculations. The new data are also referenced to the finding of ash beds in more distal areas, which were included in new isopach maps for the two sub-Plinian eruptions. The results show that for both eruptions the distribution of the primary deposits is wider than previously known. A consequence of these results is that a wider areal impact should be expected in terms of civil protection, as the sub-Plinian scenario is the reference one for a future large eruption of Vesuvius. Such a distribution of the pyroclastic deposits directly affects the one of the lahar deposits, also because a significant remobilization took place during and after the studied eruptions, which involved distal phreatomagmatic ash. From these integrated analyses, it was possible to constrain the timing of the deposition and the kind of deposits remobilized (pyroclastic fall vs. flow), and it was possible to calculate the velocities and dynamic pressures of the lahars and ultimately infer the lahar transport and emplacement mechanisms. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas even at distances of several to tens of kilometers from active volcanoes. This especially applies to large parts of the densely populated areas around Somma–Vesuvius up to the nearby Apennine valleys.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"53 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Veleda A. P. Muller, Pietro Sternai, Christian Sue
Abstract. An asthenospheric window underneath much of the South American continent increases the heat flow in the southern Patagonian Andes where glacial–interglacial cycles drive the building and melting of the Patagonian Icefields since the latest Miocene. The Last Glacial Maximum (LGM) was reached ∼26 000 yr BP (years before present). Significant deglaciation onsets between 21 000 and 17 000 yr BP were subject to an acceleration since the Little Ice Age (LIA), which was ∼400 yr BP. Fast uplift rates of up to 41±3 mm yr−1 are measured by global navigation satellite system (GNSS) around the Southern Patagonian Icefield and are currently ascribed to post-LIA lithospheric rebound, but the possible longer-term post-LGM rebound is poorly constrained. These uplift rates, in addition, are 1 order of magnitude higher than those measured on other glaciated orogens (e.g. the European Alps), which raises questions about the role of the asthenospheric window in affecting the vertical surface displacement rates. Here, we perform geodynamic thermo-mechanical numerical modelling to estimate the surface uplift rates induced by post-LIA and post-LGM deglaciation, accounting for temperature-dependent rheologies and different thermal regimes in the asthenosphere. Our modelled maximum post-glacial rebound matches the observed uplift rate budget only when both post-LIA and post-LGM deglaciation are accounted for and only if a standard continental asthenospheric mantle potential temperature is increased by 150–200 °C. The asthenospheric window thus plays a key role in controlling the magnitude of presently observed uplift rates in the southern Patagonian Andes.
{"title":"Fast uplift in the southern Patagonian Andes due to long- and short-term deglaciation and the asthenospheric window underneath","authors":"Veleda A. P. Muller, Pietro Sternai, Christian Sue","doi":"10.5194/se-15-387-2024","DOIUrl":"https://doi.org/10.5194/se-15-387-2024","url":null,"abstract":"Abstract. An asthenospheric window underneath much of the South American continent increases the heat flow in the southern Patagonian Andes where glacial–interglacial cycles drive the building and melting of the Patagonian Icefields since the latest Miocene. The Last Glacial Maximum (LGM) was reached ∼26 000 yr BP (years before present). Significant deglaciation onsets between 21 000 and 17 000 yr BP were subject to an acceleration since the Little Ice Age (LIA), which was ∼400 yr BP. Fast uplift rates of up to 41±3 mm yr−1 are measured by global navigation satellite system (GNSS) around the Southern Patagonian Icefield and are currently ascribed to post-LIA lithospheric rebound, but the possible longer-term post-LGM rebound is poorly constrained. These uplift rates, in addition, are 1 order of magnitude higher than those measured on other glaciated orogens (e.g. the European Alps), which raises questions about the role of the asthenospheric window in affecting the vertical surface displacement rates. Here, we perform geodynamic thermo-mechanical numerical modelling to estimate the surface uplift rates induced by post-LIA and post-LGM deglaciation, accounting for temperature-dependent rheologies and different thermal regimes in the asthenosphere. Our modelled maximum post-glacial rebound matches the observed uplift rate budget only when both post-LIA and post-LGM deglaciation are accounted for and only if a standard continental asthenospheric mantle potential temperature is increased by 150–200 °C. The asthenospheric window thus plays a key role in controlling the magnitude of presently observed uplift rates in the southern Patagonian Andes.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"1 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-03DOI: 10.5194/egusphere-2024-508
Abdelkader El Maz, Alain Vauchez, Jean-Marie Dautria
Abstract. The study of metapelitic sillimanite- and garnet-bearing granulite xenoliths brought to the surface by the basanite of the 650 ka Tafraoute maar shed new light on the lower crust of the Tabular Middle Atlas (Morocco). Two main types of granulites are distinguished: (1) layered quartzo-feldspathic and (2) unlayered restitic. Mineralogy, petrology, P-T estimates and EBSD data support that these granulites underwent two successive tectono-metamorphic events, before their entrapment in lava. During the first event, probably the Hercynian orogeny, the Tafraoute lower crust acquired its foliation and primary paragenesis likely including kyanite: it yields P, T conditions of 1.1 ± 0.1 GPa and 850–880 °C. The second event corresponds to a reheating up to ultrahigh temperatures (1050 ± 50 °C) under slightly lower pressure conditions (0.9 ± 0.1 GPa). This led first to the transformation of kyanite into large prismatic sillimanite. The latter displays uncommon evidence of dislocation-creep deformation of moderate intensity that points to a tectonic episode occurring after their formation. After deformation has stopped, a reaction between sillimanite and garnet resulted in the crystallization of orthopyroxene and spinel deformation-free coronas around garnets. Approaching the peak of temperature, anhydrous partial melting of quartzo-feldspathic layers likely occurred and the resulting felsic melt spread into the rocks. This reheating event might be the consequence of the Late Permian to Mid-Jurassic rifting that preceded the formation of the Middle Atlas range, possibly associated with underplating of hot gabbroic magma. This event was followed by gradual cooling down to ~800 °C, leading to static crystallization of the felsic melt in the quartzo-feldspathic granulites. The last event susceptible to have affected the lower crust is the alkali magmatism active in the Middle Atlas during the Mio-Plio-Quaternary. In this context, the origin of restitic granulites is questionable. It may result either from the thermal event associated to the pre-alpine rifting, or from the emplacement of basaltic dykes in the lower crust before the quaternary eruption of the Tafraoute volcano. During this eruption, the studied granulites were entrapped in the ascending lava and very quickly transferred up to the surface, triggering the formation of small vesicular glass pockets. This study highlights the contrasted post-Hercynian evolution of the lower crust in the northern coastal alpine orogen (Rif) and the Tabular Middle Atlas: the first one underwent a tectonic exhumation without reheating during the Alpine orogeny, while the second one is characterized by a reheating to ultra-high temperature, probably during the pre-alpine rifting, but was probably not or very little affected by the alpine events.
{"title":"Post-hercynian ultra-high temperature tectono-metamorphic evolution of the Middle Atlas lower crust (Central Morocco) revealed by metapelitic granulites xenoliths","authors":"Abdelkader El Maz, Alain Vauchez, Jean-Marie Dautria","doi":"10.5194/egusphere-2024-508","DOIUrl":"https://doi.org/10.5194/egusphere-2024-508","url":null,"abstract":"<strong>Abstract.</strong> The study of metapelitic sillimanite- and garnet-bearing granulite xenoliths brought to the surface by the basanite of the 650 ka Tafraoute maar shed new light on the lower crust of the Tabular Middle Atlas (Morocco). Two main types of granulites are distinguished: (1) layered quartzo-feldspathic and (2) unlayered restitic. Mineralogy, petrology, P-T estimates and EBSD data support that these granulites underwent two successive tectono-metamorphic events, before their entrapment in lava. During the first event, probably the Hercynian orogeny, the Tafraoute lower crust acquired its foliation and primary paragenesis likely including kyanite: it yields P, T conditions of 1.1 ± 0.1 GPa and 850–880 °C. The second event corresponds to a reheating up to ultrahigh temperatures (1050 ± 50 °C) under slightly lower pressure conditions (0.9 ± 0.1 GPa). This led first to the transformation of kyanite into large prismatic sillimanite. The latter displays uncommon evidence of dislocation-creep deformation of moderate intensity that points to a tectonic episode occurring after their formation. After deformation has stopped, a reaction between sillimanite and garnet resulted in the crystallization of orthopyroxene and spinel deformation-free coronas around garnets. Approaching the peak of temperature, anhydrous partial melting of quartzo-feldspathic layers likely occurred and the resulting felsic melt spread into the rocks. This reheating event might be the consequence of the Late Permian to Mid-Jurassic rifting that preceded the formation of the Middle Atlas range, possibly associated with underplating of hot gabbroic magma. This event was followed by gradual cooling down to ~800 °C, leading to static crystallization of the felsic melt in the quartzo-feldspathic granulites. The last event susceptible to have affected the lower crust is the alkali magmatism active in the Middle Atlas during the Mio-Plio-Quaternary. In this context, the origin of restitic granulites is questionable. It may result either from the thermal event associated to the pre-alpine rifting, or from the emplacement of basaltic dykes in the lower crust before the quaternary eruption of the Tafraoute volcano. During this eruption, the studied granulites were entrapped in the ascending lava and very quickly transferred up to the surface, triggering the formation of small vesicular glass pockets. This study highlights the contrasted post-Hercynian evolution of the lower crust in the northern coastal alpine orogen (Rif) and the Tabular Middle Atlas: the first one underwent a tectonic exhumation without reheating during the Alpine orogeny, while the second one is characterized by a reheating to ultra-high temperature, probably during the pre-alpine rifting, but was probably not or very little affected by the alpine events.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"46 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Laura Sandri, Mattia de' Michieli Vitturi, Antonio Costa, Mauro Antonio Di Vito, Ilaria Rucco, Domenico Maria Doronzo, Marina Bisson, Roberto Gianardi, Sandro de Vita, Roberto Sulpizio
Abstract. In this study we present a novel general methodology for probabilistic volcanic hazard assessment (PVHA) for lahars. We apply the methodology to perform a probabilistic assessment in the Campanian Plain (southern Italy), focusing on syn-eruptive lahars from a reference size eruption from Somma–Vesuvius. We take advantage of new field data relative to volcaniclastic flow deposits in the target region (Di Vito et al., 2024b) and recent improvements in modelling lahars (de' Michieli Vitturi et al., 2024). The former allowed defining proper probability density functions for the parameters related to the flow initial conditions, and the latter allowed computationally faster model runs. In this way, we are able to explore the effects of uncertainty in the initial flow conditions on the invasion of lahars in the target area by sampling coherent sets of values for the input model parameters and performing a large number of simulations. We also account for the uncertainty in the position of lahar generation by running the analysis on 11 different catchments threatening the Campanian Plain. The post-processing of the simulation outputs led to the production of hazard curves for the maximum flow thickness reached on a grid of points covering the Campanian Plain. By cutting the hazard curves at selected threshold values, we produce a portfolio of hazard maps and probability maps for the maximum flow thickness. We also produce hazard surface and probability maps for the simultaneous exceeding of pairs of thresholds in flow thickness and dynamic pressure. The latter hazard products represent, on one hand, a novel product in PVHA for lahars and, on the other hand, a useful means of impact assessment by assigning a probability to the occurrence of lahars that simultaneously have a relevant flow thickness and large dynamic pressure.
{"title":"Lahar events in the last 2000 years from Vesuvius eruptions – Part 3: Hazard assessment over the Campanian Plain","authors":"Laura Sandri, Mattia de' Michieli Vitturi, Antonio Costa, Mauro Antonio Di Vito, Ilaria Rucco, Domenico Maria Doronzo, Marina Bisson, Roberto Gianardi, Sandro de Vita, Roberto Sulpizio","doi":"10.5194/se-15-459-2024","DOIUrl":"https://doi.org/10.5194/se-15-459-2024","url":null,"abstract":"Abstract. In this study we present a novel general methodology for probabilistic volcanic hazard assessment (PVHA) for lahars. We apply the methodology to perform a probabilistic assessment in the Campanian Plain (southern Italy), focusing on syn-eruptive lahars from a reference size eruption from Somma–Vesuvius. We take advantage of new field data relative to volcaniclastic flow deposits in the target region (Di Vito et al., 2024b) and recent improvements in modelling lahars (de' Michieli Vitturi et al., 2024). The former allowed defining proper probability density functions for the parameters related to the flow initial conditions, and the latter allowed computationally faster model runs. In this way, we are able to explore the effects of uncertainty in the initial flow conditions on the invasion of lahars in the target area by sampling coherent sets of values for the input model parameters and performing a large number of simulations. We also account for the uncertainty in the position of lahar generation by running the analysis on 11 different catchments threatening the Campanian Plain. The post-processing of the simulation outputs led to the production of hazard curves for the maximum flow thickness reached on a grid of points covering the Campanian Plain. By cutting the hazard curves at selected threshold values, we produce a portfolio of hazard maps and probability maps for the maximum flow thickness. We also produce hazard surface and probability maps for the simultaneous exceeding of pairs of thresholds in flow thickness and dynamic pressure. The latter hazard products represent, on one hand, a novel product in PVHA for lahars and, on the other hand, a useful means of impact assessment by assigning a probability to the occurrence of lahars that simultaneously have a relevant flow thickness and large dynamic pressure.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"97 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mattia de' Michieli Vitturi, Antonio Costa, Mauro A. Di Vito, Laura Sandri, Domenico M. Doronzo
Abstract. In this paper we present a new model for the simulation of lahars based on the depth-averaged code IMEX-SfloW2D with new governing and constitutive equations introduced to better describe the dynamics of lahars. A thorough sensitivity analysis is carried out to identify the critical processes (such as erosion and deposition) and parameters (both numerical and physical) controlling lahar runout using both synthetic and real case topographies. In particular, an application of the model to a syn-eruptive lahar from a reference size eruption from Somma–Vesuvius, affecting the Campanian Plain (southern Italy), described in Di Vito et al. (2024), is used in this work for the sensitivity analysis. Effects of erosion and deposition are investigated by comparing simulations with and without these processes. By comparing flow thickness and area covered by the flow and their evolution with time, we show that the modelling of both the processes is important to properly simulate the effects of the bulking and debulking as well as the associated changes in rheology. From a computational point of view, the comparisons of simulations obtained for different numerical grids (from 25 to 100 m), scheme order, and grain size discretization were useful to find a good compromise between resolution and computational speed. The companion paper by Sandri et al. (2024) shows an application of the presented model for probabilistic volcanic hazard assessment for lahars from Vesuvius deposits in the Neapolitan area.
{"title":"Lahar events in the last 2000 years from Vesuvius eruptions – Part 2: Formulation and validation of a computational model based on a shallow layer approach","authors":"Mattia de' Michieli Vitturi, Antonio Costa, Mauro A. Di Vito, Laura Sandri, Domenico M. Doronzo","doi":"10.5194/se-15-437-2024","DOIUrl":"https://doi.org/10.5194/se-15-437-2024","url":null,"abstract":"Abstract. In this paper we present a new model for the simulation of lahars based on the depth-averaged code IMEX-SfloW2D with new governing and constitutive equations introduced to better describe the dynamics of lahars. A thorough sensitivity analysis is carried out to identify the critical processes (such as erosion and deposition) and parameters (both numerical and physical) controlling lahar runout using both synthetic and real case topographies. In particular, an application of the model to a syn-eruptive lahar from a reference size eruption from Somma–Vesuvius, affecting the Campanian Plain (southern Italy), described in Di Vito et al. (2024), is used in this work for the sensitivity analysis. Effects of erosion and deposition are investigated by comparing simulations with and without these processes. By comparing flow thickness and area covered by the flow and their evolution with time, we show that the modelling of both the processes is important to properly simulate the effects of the bulking and debulking as well as the associated changes in rheology. From a computational point of view, the comparisons of simulations obtained for different numerical grids (from 25 to 100 m), scheme order, and grain size discretization were useful to find a good compromise between resolution and computational speed. The companion paper by Sandri et al. (2024) shows an application of the presented model for probabilistic volcanic hazard assessment for lahars from Vesuvius deposits in the Neapolitan area.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"59 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. This work investigates the influence of rheological contrasts on the nucleation and behavior of strike-slip faults. To achieve this, we have carried out a series of brittle-viscous strike-slip shear analogue models, using quartz sand and microbeads as granular materials with different internal friction and cohesion values. Particle Imaging Velocimetry (PIV) was applied to time-series of surface images to calculate incremental and cumulative strains. Understanding how strike-slip faults nucleate and interact in the heterogeneous upper crust is relevant in seismic hazard analysis and geothermal and hydrocarbon exploration. To reproduce the heterogeneity of the upper crust, three sets of experiments we performed: 1) upper layer composed either of quartz sand or microbeads; 2) upper layer with a vertical contrast i.e., quartz sand surrounded by microbeads and vice-versa; and 3) same set-up as in the previous set but changing the orientation of the vertical contrast. Our study shows that the introduction of an upper crustal vertical contrast influences the behavior and evolution of strike-slip faults. The models containing a vertical contrast were more complex and induced a compartmentalization of the model. The initial fault strike is related to the material’s properties. However, this initial strike changes when faults crosscut the materials with less internal friction angle clockwise, and anticlockwise when the contrast has higher internal friction angle. Areas containing materials with less internal friction angle take longer to localized the deformation, but they show a greater number of faults. The biggest increase in the number of synthetic and antithetic faults occurs with the introduction of vertical contrast. These results were compared with the intraplate fault systems of the NW Iberian Peninsula, focusing on the Penacova-Régua-Verin and Manteigas-Vilariça-Bragança fault systems. They are major left-lateral faults that cross-cut lithologies characterized by vertical rheological contrasts, with deformation patterns similar to those observed in our analogue models.
{"title":"The influence of vertical lithological contrasts on strike-slip fault behavior: Insights from analogue models","authors":"Sandra González-Muñoz, Guido Schreurs, Timothy Schmid, Fidel Martín-González","doi":"10.5194/egusphere-2024-852","DOIUrl":"https://doi.org/10.5194/egusphere-2024-852","url":null,"abstract":"<strong>Abstract.</strong> This work investigates the influence of rheological contrasts on the nucleation and behavior of strike-slip faults. To achieve this, we have carried out a series of brittle-viscous strike-slip shear analogue models, using quartz sand and microbeads as granular materials with different internal friction and cohesion values. Particle Imaging Velocimetry (PIV) was applied to time-series of surface images to calculate incremental and cumulative strains. Understanding how strike-slip faults nucleate and interact in the heterogeneous upper crust is relevant in seismic hazard analysis and geothermal and hydrocarbon exploration. To reproduce the heterogeneity of the upper crust, three sets of experiments we performed: 1) upper layer composed either of quartz sand or microbeads; 2) upper layer with a vertical contrast i.e., quartz sand surrounded by microbeads and vice-versa; and 3) same set-up as in the previous set but changing the orientation of the vertical contrast. Our study shows that the introduction of an upper crustal vertical contrast influences the behavior and evolution of strike-slip faults. The models containing a vertical contrast were more complex and induced a compartmentalization of the model. The initial fault strike is related to the material’s properties. However, this initial strike changes when faults crosscut the materials with less internal friction angle clockwise, and anticlockwise when the contrast has higher internal friction angle. Areas containing materials with less internal friction angle take longer to localized the deformation, but they show a greater number of faults. The biggest increase in the number of synthetic and antithetic faults occurs with the introduction of vertical contrast. These results were compared with the intraplate fault systems of the NW Iberian Peninsula, focusing on the Penacova-Régua-Verin and Manteigas-Vilariça-Bragança fault systems. They are major left-lateral faults that cross-cut lithologies characterized by vertical rheological contrasts, with deformation patterns similar to those observed in our analogue models.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"7 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140324796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Relying on geological data to construct 3D models can provide a more intuitive and easily comprehensible spatial perspective. This process aids in exploring underground spatial structures and geological evolutionary processes, providing essential data and assistance for the exploration of geological resources, energy development, engineering decision-making, and various other applications. As one of the methods for 3D geological modeling, multipoint statistics can effectively describe and reconstruct the intricate geometric shapes of nonlinear geological bodies. However, existing multipoint statistics algorithms still face challenges in efficiently extracting and reconstructing the global spatial distribution characteristics of geological objects. Moreover, they lack a data-driven modeling framework that integrates diverse sources of heterogeneous data. This research introduces a novel approach that combines multipoint statistics with multimodal deep artificial neural networks and constructs the 3D crustal P-wave velocity structure model of the South China Sea by using 44 OBS forward profiles, gravity anomalies, magnetic anomalies and topographic relief data. The experimental results demonstrate that the new approach surpasses multipoint statistics and Kriging interpolation methods, and can generate a more accurate 3D geological model through the integration of multiple geophysical data. Furthermore, the reliability of the 3D crustal P-wave velocity structure model, established using the novel method, was corroborated through visual and statistical analyses. This model intuitively delineates the spatial distribution characteristics of the crustal velocity structure in the South China Sea, thereby offering a foundational data basis for researchers to gain a more comprehensive understanding of the geological evolution process within this region.
摘要依靠地质数据构建三维模型可以提供更直观、更易于理解的空间视角。这一过程有助于探索地下空间结构和地质演化过程，为地质资源勘探、能源开发、工程决策和其他各种应用提供必要的数据和帮助。作为三维地质建模的方法之一，多点统计可以有效地描述和重建非线性地质体错综复杂的几何形状。然而，现有的多点统计算法在有效提取和重建地质体的全局空间分布特征方面仍面临挑战。此外，这些算法还缺乏数据驱动的建模框架，无法整合不同来源的异构数据。本研究介绍了一种将多点统计与多模态深度人工神经网络相结合的新方法，并利用 44 个 OBS 前向剖面、重力异常、磁异常和地形起伏数据构建了南海三维地壳 P 波速度结构模型。实验结果表明，新方法超越了多点统计和克里金插值方法，可以通过整合多种地球物理数据生成更精确的三维地质模型。此外，利用新方法建立的三维地壳 P 波速度结构模型的可靠性也通过直观和统计分析得到了证实。该模型直观地描述了南海地壳速度结构的空间分布特征，从而为研究人员更全面地了解该区域的地质演化过程提供了基础数据依据。
{"title":"3D Geo-Modeling Framework for Multisource Heterogeneous Data Fusion Based on Multimodal Deep Learning and Multipoint Statistics: A case study in South China Sea","authors":"Hengguang Liu, Shaohong Xia, Chaoyan Fan, Changrong Zhang","doi":"10.5194/egusphere-2024-684","DOIUrl":"https://doi.org/10.5194/egusphere-2024-684","url":null,"abstract":"<strong>Abstract.</strong> Relying on geological data to construct 3D models can provide a more intuitive and easily comprehensible spatial perspective. This process aids in exploring underground spatial structures and geological evolutionary processes, providing essential data and assistance for the exploration of geological resources, energy development, engineering decision-making, and various other applications. As one of the methods for 3D geological modeling, multipoint statistics can effectively describe and reconstruct the intricate geometric shapes of nonlinear geological bodies. However, existing multipoint statistics algorithms still face challenges in efficiently extracting and reconstructing the global spatial distribution characteristics of geological objects. Moreover, they lack a data-driven modeling framework that integrates diverse sources of heterogeneous data. This research introduces a novel approach that combines multipoint statistics with multimodal deep artificial neural networks and constructs the 3D crustal P-wave velocity structure model of the South China Sea by using 44 OBS forward profiles, gravity anomalies, magnetic anomalies and topographic relief data. The experimental results demonstrate that the new approach surpasses multipoint statistics and Kriging interpolation methods, and can generate a more accurate 3D geological model through the integration of multiple geophysical data. Furthermore, the reliability of the 3D crustal P-wave velocity structure model, established using the novel method, was corroborated through visual and statistical analyses. This model intuitively delineates the spatial distribution characteristics of the crustal velocity structure in the South China Sea, thereby offering a foundational data basis for researchers to gain a more comprehensive understanding of the geological evolution process within this region.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"53 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140317065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-15DOI: 10.5194/egusphere-2024-386
Delphine Charpentier, Gaétan Milesi, Pierre Labaume, Ahmed Abd Elmola, Martine Buatier, Pierre Lanari, Manuel Muñoz
Abstract. In mountain ranges, crustal-scale faults localize multiple episodes of deformation. It is therefore common to observe current or past geothermal systems along these structures. Understanding the fluid circulation channelized in fault zones is essential to characterize the thermo-chemical evolution of associated hydrothermal systems. We present a study of a paleo-system of the Pic de Port-Vieux thrust fault. This fault is a second-order thrust associated with the Gavarnie thrust in the Axial Zone of the Pyrenees. The study focused on phyllosilicates, which permit to constrain the evolution of temperature and redox of fluids at the scale of the fault system. Combined X-ray absorption near-edge structure (XANES) spectroscopy and electron probe microanalysis (EPMA) on synkinematic chlorite, closely linked to microstructural observations were performed in both the core and damage zones of the fault zone. Regardless of their microstructural position, chlorite from the damage zone contains iron and magnesium (Fetotal/(Fetotal+Mg) about 0.4), with Fe3+ accounting for about 30 % of the total iron. Chlorite in the core zone is enriched in total iron, but individual Fe3+/Fetotal ratios range from 15 % to 40 % depending on the microstructural position of the grain. Homogeneous temperature conditions about 300 °C have been obtained by chlorite thermometry. A scenario is proposed for the evolution of fluid-rock interaction conditions at the scale of the fault zone. It involves the circulation of a single hydrothermal fluid with homogeneous temperature but several redox properties. A highly reducing fluid evolves due to redox reactions involving progressive dissolution of hematite, accompanied by crystallization of Fe2+-rich and Fe3+-rich chlorite in the core zone.
{"title":"Evolution of fluid redox in a fault zone of the Pic de Port-Vieux thrust in the Pyrenees Axial Zone (Spain)","authors":"Delphine Charpentier, Gaétan Milesi, Pierre Labaume, Ahmed Abd Elmola, Martine Buatier, Pierre Lanari, Manuel Muñoz","doi":"10.5194/egusphere-2024-386","DOIUrl":"https://doi.org/10.5194/egusphere-2024-386","url":null,"abstract":"<strong>Abstract.</strong> In mountain ranges, crustal-scale faults localize multiple episodes of deformation. It is therefore common to observe current or past geothermal systems along these structures. Understanding the fluid circulation channelized in fault zones is essential to characterize the thermo-chemical evolution of associated hydrothermal systems. We present a study of a paleo-system of the Pic de Port-Vieux thrust fault. This fault is a second-order thrust associated with the Gavarnie thrust in the Axial Zone of the Pyrenees. The study focused on phyllosilicates, which permit to constrain the evolution of temperature and redox of fluids at the scale of the fault system. Combined X-ray absorption near-edge structure (XANES) spectroscopy and electron probe microanalysis (EPMA) on synkinematic chlorite, closely linked to microstructural observations were performed in both the core and damage zones of the fault zone. Regardless of their microstructural position, chlorite from the damage zone contains iron and magnesium (Fe<sub>total</sub>/(Fe<sub>total</sub>+Mg) about 0.4), with Fe<sup>3+</sup> accounting for about 30 % of the total iron. Chlorite in the core zone is enriched in total iron, but individual Fe<sup>3+</sup>/Fe<sub>total</sub> ratios range from 15 % to 40 % depending on the microstructural position of the grain. Homogeneous temperature conditions about 300 °C have been obtained by chlorite thermometry. A scenario is proposed for the evolution of fluid-rock interaction conditions at the scale of the fault zone. It involves the circulation of a single hydrothermal fluid with homogeneous temperature but several redox properties. A highly reducing fluid evolves due to redox reactions involving progressive dissolution of hematite, accompanied by crystallization of Fe<sup>2+</sup>-rich and Fe<sup>3+</sup>-rich chlorite in the core zone.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"23 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140148070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Farbod Khosro Anjom, Frank Adler, Laura Valentina Socco
Abstract. The acquisition of seismic exploration data in remote locations presents several logistical and economic criticalities. The irregular distribution of sources and/or receivers facilitates seismic acquisition operations in these areas. A convenient approach is to deploy nodal receivers on a regular grid and to use sources only in accessible locations, creating an irregular source–receiver layout. It is essential to evaluate, adapt, and verify processing workflows, specifically for near-surface velocity model estimation using surface-wave analysis, when working with these types of datasets. In this study, we applied three surface-wave techniques (i.e., wavelength–depth (W/D) method, laterally constrained inversion (LCI), and surface-wave tomography (SWT)) to a large-scale 3D dataset obtained from a hard-rock site using the irregular source–receiver acquisition method. The methods were fine-tuned for the data obtained from hard-rock sites, which typically exhibit a low signal-to-noise ratio. The wavelength–depth method is a data transformation method that is based on a relationship between skin depth and surface-wave wavelength and provides both S- and P-wave velocity (Vs and Vp) models. We used Poisson's ratios estimated through the wavelength–depth method to constrain the laterally constrained inversion and surface-wave tomography and to retrieve both Vs and Vp also from these methods. The pseudo-3D Vs and Vp models were obtained down to 140 m depth over an area of approximately 900 × 1500 m2. The estimated models from the methods matched the geological information available for the site. A difference of less than 6 % was observed between the estimated Vs models from the three methods, whereas this value was 7.1 % for the retrieved Vp models. The methods were critically compared in terms of resolution and efficiency, which provides valuable insights into the potential of surface-wave analysis for estimating near-surface models at hard-rock sites.
摘要在偏远地区采集地震勘探数据存在若干后勤和经济方面的关键问题。震源和/或接收器的不规则分布有利于这些地区的地震采集作业。一种方便的方法是在规则的网格上部署节点接收器，只在可到达的地点使用震源，形成不规则的震源-接收器布局。在处理这类数据集时，必须评估、调整和验证处理工作流程，特别是利用面波分析进行近地表速度模型估算的工作流程。在这项研究中，我们将三种面波技术（即波长-深度（W/D）法、横向约束反演（LCI）和面波层析成像（SWT））应用于采用不规则源-接收器采集方法从硬岩场地获得的大规模三维数据集。这些方法针对从硬岩地点获得的数据进行了微调，硬岩地点通常信噪比较低。波深法是一种数据转换方法，它基于表皮深度和表面波波长之间的关系，并提供 S 波和 P 波速度（Vs 和 Vp）模型。我们使用波长深度法估算的泊松比来约束横向约束反演和面波层析成像，并从这些方法中获取 Vs 和 Vp。在大约 900 × 1500 平方米的区域内，获得了深度达 140 米的伪三维 Vs 和 Vp 模型。这些方法估算出的模型与该地点现有的地质信息相吻合。三种方法估算的 Vs 模型之间的差异小于 6%，而检索的 Vp 模型之间的差异为 7.1%。这些方法在分辨率和效率方面进行了严格的比较，为了解面波分析在估算硬岩地点近地表模型方面的潜力提供了宝贵的见解。
{"title":"Comparison of surface-wave techniques to estimate S- and P-wave velocity models from active seismic data","authors":"Farbod Khosro Anjom, Frank Adler, Laura Valentina Socco","doi":"10.5194/se-15-367-2024","DOIUrl":"https://doi.org/10.5194/se-15-367-2024","url":null,"abstract":"Abstract. The acquisition of seismic exploration data in remote locations presents several logistical and economic criticalities. The irregular distribution of sources and/or receivers facilitates seismic acquisition operations in these areas. A convenient approach is to deploy nodal receivers on a regular grid and to use sources only in accessible locations, creating an irregular source–receiver layout. It is essential to evaluate, adapt, and verify processing workflows, specifically for near-surface velocity model estimation using surface-wave analysis, when working with these types of datasets. In this study, we applied three surface-wave techniques (i.e., wavelength–depth (W/D) method, laterally constrained inversion (LCI), and surface-wave tomography (SWT)) to a large-scale 3D dataset obtained from a hard-rock site using the irregular source–receiver acquisition method. The methods were fine-tuned for the data obtained from hard-rock sites, which typically exhibit a low signal-to-noise ratio. The wavelength–depth method is a data transformation method that is based on a relationship between skin depth and surface-wave wavelength and provides both S- and P-wave velocity (Vs and Vp) models. We used Poisson's ratios estimated through the wavelength–depth method to constrain the laterally constrained inversion and surface-wave tomography and to retrieve both Vs and Vp also from these methods. The pseudo-3D Vs and Vp models were obtained down to 140 m depth over an area of approximately 900 × 1500 m2. The estimated models from the methods matched the geological information available for the site. A difference of less than 6 % was observed between the estimated Vs models from the three methods, whereas this value was 7.1 % for the retrieved Vp models. The methods were critically compared in terms of resolution and efficiency, which provides valuable insights into the potential of surface-wave analysis for estimating near-surface models at hard-rock sites.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"29 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140147949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marco Fuchs, Anna Suzuki, Togo Hasumi, Philipp Blum
Abstract. The permeability of rock fractures is a crucial parameter for flow processes in the subsurface. In the last few decades, different methods were developed to investigate on permeability in fractures, such as flow-through experiments, numerical flow simulations, or empirical equations. In recent years, the topological method of persistent homology was also used to estimate the permeability of fracture networks and porous rocks but not for rough single fractures yet. Hence, we apply persistent homology analysis on a decimetre-scale, rough sandstone bedding joint. To investigate the influence of roughness, three different data sets are created to perform the analysis: (1) 200 µm, (2) 100 µm, and (3) 50 µm resolutions. All estimated permeabilities were then compared to values derived by experimental air permeameter measurements and numerical flow simulation. The results reveal that persistent homology analysis is able to estimate the permeability of a single fracture, even if it tends to slightly overestimate permeabilities compared to conventional methods. Previous studies using porous media showed the same overestimation trend. Furthermore, the expenditure of time for persistent homology analysis, as well as air permeameter measurements and numerical flow simulation, was compared, which showed that persistent homology analysis can be also an acceptable alternative method.
{"title":"Investigating rough single-fracture permeabilities with persistent homology","authors":"Marco Fuchs, Anna Suzuki, Togo Hasumi, Philipp Blum","doi":"10.5194/se-15-353-2024","DOIUrl":"https://doi.org/10.5194/se-15-353-2024","url":null,"abstract":"Abstract. The permeability of rock fractures is a crucial parameter for flow processes in the subsurface. In the last few decades, different methods were developed to investigate on permeability in fractures, such as flow-through experiments, numerical flow simulations, or empirical equations. In recent years, the topological method of persistent homology was also used to estimate the permeability of fracture networks and porous rocks but not for rough single fractures yet. Hence, we apply persistent homology analysis on a decimetre-scale, rough sandstone bedding joint. To investigate the influence of roughness, three different data sets are created to perform the analysis: (1) 200 µm, (2) 100 µm, and (3) 50 µm resolutions. All estimated permeabilities were then compared to values derived by experimental air permeameter measurements and numerical flow simulation. The results reveal that persistent homology analysis is able to estimate the permeability of a single fracture, even if it tends to slightly overestimate permeabilities compared to conventional methods. Previous studies using porous media showed the same overestimation trend. Furthermore, the expenditure of time for persistent homology analysis, as well as air permeameter measurements and numerical flow simulation, was compared, which showed that persistent homology analysis can be also an acceptable alternative method.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"160 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140115119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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