Lennart Paul, Jorge-Humberto Urrea-Quintero, Umer Fiaz, Ali Hussein, Hazem Yaghi, Henning Wessels, Ulrich Römer, Joachim Stahlmann
This work introduces a surrogate modeling approach for an emplacement drift of a deep geological repository based on Gaussian Processes (GPs). The surrogate model is used as a substitute for the high-fidelity mechanical model in many-query scenarios, such as time-dependent sensitivity analysis and calibration. Our GP-based approach emulates the behavior of an emplacement drift of a deep geological repository with significantly reduced computational time, enabling faster design iterations and effective incorporation as well as interpretation of monitoring data. Our findings show that only a few key parameters are essential for accurately reflecting in-situ conditions in complex rock salt models, which is critical for ensuring safety in deep geological disposal.
这项工作介绍了一种基于高斯过程（GPs）的深层地质储藏库位移漂移替代建模方法。代用模型可在多种查询场景中替代高保真力学模型，例如随时间变化的敏感性分析和校准。我们基于 GP 的方法模拟了深层地质资料库的位移漂移行为，大大缩短了计算时间，从而加快了设计迭代速度，并有效地纳入和解释了监测数据。我们的研究结果表明，要准确反映复杂岩盐模型的原位条件，只有几个关键参数是必不可少的，这对于确保深部地质处置的安全性至关重要。
{"title":"Gaussian Processes enabled model calibration in the context of deep geological disposal","authors":"Lennart Paul, Jorge-Humberto Urrea-Quintero, Umer Fiaz, Ali Hussein, Hazem Yaghi, Henning Wessels, Ulrich Römer, Joachim Stahlmann","doi":"arxiv-2409.02576","DOIUrl":"https://doi.org/arxiv-2409.02576","url":null,"abstract":"This work introduces a surrogate modeling approach for an emplacement drift\u0000of a deep geological repository based on Gaussian Processes (GPs). The\u0000surrogate model is used as a substitute for the high-fidelity mechanical model\u0000in many-query scenarios, such as time-dependent sensitivity analysis and\u0000calibration. Our GP-based approach emulates the behavior of an emplacement\u0000drift of a deep geological repository with significantly reduced computational\u0000time, enabling faster design iterations and effective incorporation as well as\u0000interpretation of monitoring data. Our findings show that only a few key\u0000parameters are essential for accurately reflecting in-situ conditions in\u0000complex rock salt models, which is critical for ensuring safety in deep\u0000geological disposal.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142226709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tiziano Bagnasco, Alessandro Stocchino, Michalis I. Vousdoukas, Jinghua Wang
In the present study, we performed a 53-year wave hindcast (1970-2022) for a significant portion of the South China Sea (SCS) with an unstructured mesh that reaches considerably high resolution along the coasts of the Guangdong province (China). The adopted modeling approach is based on the fully two-way coupled SCHISM-WWMIII numerical suite. The model was forced with ERA5 wind velocities that were compared to IFREMER altimeter wind velocities and then bias-corrected for a more accurate treatment of the wind component. Eight major tidal harmonics extracted from FES2014 were imposed to the open boundaries. After a preliminary mesh independence analysis, the model results have been validated against satellite altimeter observations retrieved from the European Space Agency database spanning the period from 1992 to 2019. Moreover, 28 year in-situ measurements from two coastal wave buoys and data from four tidal gauge stations (approximately 20 years) were used to test the nearshore skills of the model. Several statistical indicators have been used to evaluate the offshore and nearshore performance of the model results in terms of the main wave parameters (significant wave height, peak wave period, mean wave direction) and water levels. All statistical metrics suggest that the present hindcast improved the predictions of waves and water levels compared to previous datasets, especially in the coastal regions. The high spatial resolution together with a full coupling allowed the model to capture and simulate processes that are induced by the non-linear interactions between waves and currents, especially nearshore.
{"title":"A two-way coupled high resolution wave hindcast for the South China Sea","authors":"Tiziano Bagnasco, Alessandro Stocchino, Michalis I. Vousdoukas, Jinghua Wang","doi":"arxiv-2409.02472","DOIUrl":"https://doi.org/arxiv-2409.02472","url":null,"abstract":"In the present study, we performed a 53-year wave hindcast (1970-2022) for a\u0000significant portion of the South China Sea (SCS) with an unstructured mesh that\u0000reaches considerably high resolution along the coasts of the Guangdong province\u0000(China). The adopted modeling approach is based on the fully two-way coupled\u0000SCHISM-WWMIII numerical suite. The model was forced with ERA5 wind velocities\u0000that were compared to IFREMER altimeter wind velocities and then bias-corrected\u0000for a more accurate treatment of the wind component. Eight major tidal\u0000harmonics extracted from FES2014 were imposed to the open boundaries. After a\u0000preliminary mesh independence analysis, the model results have been validated\u0000against satellite altimeter observations retrieved from the European Space\u0000Agency database spanning the period from 1992 to 2019. Moreover, 28 year\u0000in-situ measurements from two coastal wave buoys and data from four tidal gauge\u0000stations (approximately 20 years) were used to test the nearshore skills of the\u0000model. Several statistical indicators have been used to evaluate the offshore\u0000and nearshore performance of the model results in terms of the main wave\u0000parameters (significant wave height, peak wave period, mean wave direction) and\u0000water levels. All statistical metrics suggest that the present hindcast\u0000improved the predictions of waves and water levels compared to previous\u0000datasets, especially in the coastal regions. The high spatial resolution\u0000together with a full coupling allowed the model to capture and simulate\u0000processes that are induced by the non-linear interactions between waves and\u0000currents, especially nearshore.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142226731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jing Sun, Sigmund Slang, Thomas Elboth, Thomas Larsen Greiner, Steven McDonald, Leiv-J Gelius
Marine seismic interference noise occurs when energy from nearby marine seismic source vessels is recorded during a seismic survey. Such noise tends to be well preserved over large distances and cause coherent artifacts in the recorded data. Over the years, the industry has developed various denoising techniques for seismic interference removal, but although well performing they are still time-consuming in use. Machine-learning based processing represents an alternative approach, which may significantly improve the computational efficiency. In case of conventional images, autoencoders are frequently employed for denoising purposes. However, due to the special characteristics of seismic data as well as the noise, autoencoders failed in the case of marine seismic interference noise. We therefore propose the use of a customized U-Net design with element-wise summation as part of the skip-connection blocks to handle the vanishing gradient problem and to ensure information fusion between high- and low-level features. To secure a realistic study, only seismic field data were employed, including 25000 training examples. The customized U-Net was found to perform well leaving only minor residuals, except for the case when seismic interference noise comes from the side. We further demonstrate that such noise can be treated by slightly increasing the depth of our network. Although our customized U-Net does not outperform a standard commercial algorithm in quality, it can (after proper training) read and process one single shot gather in approximately 0.02s. This is significantly faster than any existing industry denoising algorithm. In addition, the proposed network processes shot gathers in a sequential order, which is an advantage compared with industry algorithms that typically require a multi-shot input to break the coherency of the noise.
{"title":"Attenuation of marine seismic interference noise employing a customized U-Net","authors":"Jing Sun, Sigmund Slang, Thomas Elboth, Thomas Larsen Greiner, Steven McDonald, Leiv-J Gelius","doi":"arxiv-2409.01673","DOIUrl":"https://doi.org/arxiv-2409.01673","url":null,"abstract":"Marine seismic interference noise occurs when energy from nearby marine\u0000seismic source vessels is recorded during a seismic survey. Such noise tends to\u0000be well preserved over large distances and cause coherent artifacts in the\u0000recorded data. Over the years, the industry has developed various denoising\u0000techniques for seismic interference removal, but although well performing they\u0000are still time-consuming in use. Machine-learning based processing represents\u0000an alternative approach, which may significantly improve the computational\u0000efficiency. In case of conventional images, autoencoders are frequently\u0000employed for denoising purposes. However, due to the special characteristics of\u0000seismic data as well as the noise, autoencoders failed in the case of marine\u0000seismic interference noise. We therefore propose the use of a customized U-Net\u0000design with element-wise summation as part of the skip-connection blocks to\u0000handle the vanishing gradient problem and to ensure information fusion between\u0000high- and low-level features. To secure a realistic study, only seismic field\u0000data were employed, including 25000 training examples. The customized U-Net was\u0000found to perform well leaving only minor residuals, except for the case when\u0000seismic interference noise comes from the side. We further demonstrate that\u0000such noise can be treated by slightly increasing the depth of our network.\u0000Although our customized U-Net does not outperform a standard commercial\u0000algorithm in quality, it can (after proper training) read and process one\u0000single shot gather in approximately 0.02s. This is significantly faster than\u0000any existing industry denoising algorithm. In addition, the proposed network\u0000processes shot gathers in a sequential order, which is an advantage compared\u0000with industry algorithms that typically require a multi-shot input to break the\u0000coherency of the noise.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Beatriz Galindo-Prieto, Ian S. Mudway, Johan Linderholm, Paul Geladi
In this paper, the potential use of multi-block chemometric methods to provide improved unsupervised classification of compositionally complex materials through the integration of multi-modal spectrometric data sets (one XRF, two NIR, and two FT-Raman) was tested. We concluded that multi-block HPLS models are effective at combining multi-modal spectrometric data to provide a more comprehensive classification of compositionally complex samples, and VIP can reduce HPLS model complexity, while increasing its data interpretability.
{"title":"Multi-block chemometric approaches to the unsupervised spectral classification of geological samples","authors":"Beatriz Galindo-Prieto, Ian S. Mudway, Johan Linderholm, Paul Geladi","doi":"arxiv-2409.04466","DOIUrl":"https://doi.org/arxiv-2409.04466","url":null,"abstract":"In this paper, the potential use of multi-block chemometric methods to\u0000provide improved unsupervised classification of compositionally complex\u0000materials through the integration of multi-modal spectrometric data sets (one\u0000XRF, two NIR, and two FT-Raman) was tested. We concluded that multi-block HPLS\u0000models are effective at combining multi-modal spectrometric data to provide a\u0000more comprehensive classification of compositionally complex samples, and VIP\u0000can reduce HPLS model complexity, while increasing its data interpretability.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142226732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Full 3D modelling of time-domain electromagnetic data requires tremendous computational resources. Consequently, simplified physics models prevail in geophysics, using a much faster but approximate (1D) forward model. We propose to join the accuracy of a 1D simplified physics model with the flexibility of coarse grids to reduce the modelling errors, thereby avoiding the full 3D accurate simulations. We exemplify our approach on airborne time-domain electromagnetic data, comparing the modelling error with the standard 3% measurement noise. We find that the modelling error depends on the specific subsurface model (electrical conductivity values, angle representing the deviation of the 1D assumption) and the specific (temporal) discretization. In our example, the computation time is decreased by a factor of 27. Our approach can offer an alternative for surrogate models, statistical relations derived from large 3D datasets, to replace the full 3D simulations.
{"title":"Joining simplified physics models with coarse grids to speed-up intractable 3D time-domain simulations","authors":"Wouter Deleersnyder, Evert Slob","doi":"arxiv-2408.17137","DOIUrl":"https://doi.org/arxiv-2408.17137","url":null,"abstract":"Full 3D modelling of time-domain electromagnetic data requires tremendous\u0000computational resources. Consequently, simplified physics models prevail in\u0000geophysics, using a much faster but approximate (1D) forward model. We propose\u0000to join the accuracy of a 1D simplified physics model with the flexibility of\u0000coarse grids to reduce the modelling errors, thereby avoiding the full 3D\u0000accurate simulations. We exemplify our approach on airborne time-domain\u0000electromagnetic data, comparing the modelling error with the standard 3%\u0000measurement noise. We find that the modelling error depends on the specific\u0000subsurface model (electrical conductivity values, angle representing the\u0000deviation of the 1D assumption) and the specific (temporal) discretization. In\u0000our example, the computation time is decreased by a factor of 27. Our approach\u0000can offer an alternative for surrogate models, statistical relations derived\u0000from large 3D datasets, to replace the full 3D simulations.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Knowledge of the underlying mechanisms of multiphase flow dynamics in porous media is crucial for optimizing subsurface engineering applications like geological carbon sequestration. However, studying the micro-mechanisms of multiphase fluid--grain interactions in the laboratory is challenging due to the difficulty in obtaining mechanical data such as force and displacement. Transitional discrete element method models coupled with pore networks offer insights into these interactions but struggle with accurate pressure prediction during pore expansion from fracturing and efficient simulation during the slow drainage of compressible fluids. To address these limitations, we develop an advanced two-way coupled hydro-mechanical discrete element method model that accurately and efficiently captures fluid--fluid and fluid--grain interactions in deformable porous media. Our model integrates an unconditionally stable implicit finite volume approach, enabling significant timesteps for advancing fluids. A pressure-volume iteration scheme dynamically balances injection-induced pressure buildup with substantial pore structure deformation, while flow front-advancing criteria precisely locate the fluid--fluid interface and adaptively refine timesteps, particularly when capillary effects block potential flow paths. The model is validated against benchmark Hele-Shaw experiments in both rigid and deformable porous media, providing quantitative insights into the micro-mechanisms governing multiphase flow. For the first time, grain-scale inputs such as viscous and capillary pressures, energies, contact forces, and flow resistances are utilized to provide a detailed understanding of micro-scale fluid--fluid and fluid--grain flow patterns and their transitions.
{"title":"Fully Coupled Implicit Hydro-Mechanical Multiphase Flow Simulation in Deformable Porous Media Using DEM","authors":"Quanwei Dai, Kang Duan, Chung-Yee Kwok","doi":"arxiv-2408.17100","DOIUrl":"https://doi.org/arxiv-2408.17100","url":null,"abstract":"Knowledge of the underlying mechanisms of multiphase flow dynamics in porous\u0000media is crucial for optimizing subsurface engineering applications like\u0000geological carbon sequestration. However, studying the micro-mechanisms of\u0000multiphase fluid--grain interactions in the laboratory is challenging due to\u0000the difficulty in obtaining mechanical data such as force and displacement.\u0000Transitional discrete element method models coupled with pore networks offer\u0000insights into these interactions but struggle with accurate pressure prediction\u0000during pore expansion from fracturing and efficient simulation during the slow\u0000drainage of compressible fluids. To address these limitations, we develop an\u0000advanced two-way coupled hydro-mechanical discrete element method model that\u0000accurately and efficiently captures fluid--fluid and fluid--grain interactions\u0000in deformable porous media. Our model integrates an unconditionally stable\u0000implicit finite volume approach, enabling significant timesteps for advancing\u0000fluids. A pressure-volume iteration scheme dynamically balances\u0000injection-induced pressure buildup with substantial pore structure deformation,\u0000while flow front-advancing criteria precisely locate the fluid--fluid interface\u0000and adaptively refine timesteps, particularly when capillary effects block\u0000potential flow paths. The model is validated against benchmark Hele-Shaw\u0000experiments in both rigid and deformable porous media, providing quantitative\u0000insights into the micro-mechanisms governing multiphase flow. For the first\u0000time, grain-scale inputs such as viscous and capillary pressures, energies,\u0000contact forces, and flow resistances are utilized to provide a detailed\u0000understanding of micro-scale fluid--fluid and fluid--grain flow patterns and\u0000their transitions.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dominique Gibert, Fernando Lopes, Vincent Courtillot, Jean-Baptiste Boulé
This book is intended for teaching Signal Analysis methods and Inverse Problems theory. It is completely open access and will remain free. It is currently illustrated with examples that we have actually encountered in geophysics, but will eventually evolve to address problems in biology. The main idea is to develop this material over time (probably every six months) and throughout our careers. Therefore, it is not yet complete and some minor points need to be corrected in this English version. A French version is also available. The MATLAB codes we used can be found at the following address: https://www.dropbox.com/scl/fi/ndi2fs3yyup64i8xyzjqd/matlab_book.zip?rlkey=j112lo5kaxvinh362frc66bcl&st=enxxx1ps&dl=0
{"title":"Information theory, Signal Analysis and Inverse Problem","authors":"Dominique Gibert, Fernando Lopes, Vincent Courtillot, Jean-Baptiste Boulé","doi":"arxiv-2408.16361","DOIUrl":"https://doi.org/arxiv-2408.16361","url":null,"abstract":"This book is intended for teaching Signal Analysis methods and Inverse\u0000Problems theory. It is completely open access and will remain free. It is\u0000currently illustrated with examples that we have actually encountered in\u0000geophysics, but will eventually evolve to address problems in biology. The main\u0000idea is to develop this material over time (probably every six months) and\u0000throughout our careers. Therefore, it is not yet complete and some minor points\u0000need to be corrected in this English version. A French version is also\u0000available. The MATLAB codes we used can be found at the following address:\u0000https://www.dropbox.com/scl/fi/ndi2fs3yyup64i8xyzjqd/matlab_book.zip?rlkey=j112lo5kaxvinh362frc66bcl&st=enxxx1ps&dl=0","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Here we critically examine the geophysical and geochemical properties of the Moon in order to identify the extent to which dynamical scenarios satisfy these observations. New joint inversions of existing lunar geophysical data (mean mass, moment of inertia, and tidal response) assuming a laterally- and vertically homogeneous lunar mantle show that, in all cases, a core with a radius of 300$pm$20 km ($sim$0.8 to 1.5 % the mass of the Moon) is required. However, an Earth-like Mg# (0.89) in the lunar mantle results in core densities (7800$pm$100 kg/m$^3$) consistent with that of Fe-Ni alloy, whereas FeO-rich compositions (Mg# = 0.80--0.84) require lower densities (6100$pm$800 kg/m$^3$). Geochemically, we use new data on mare basalts to reassess the bulk composition of the Moon for 70 elements, and show that the lunar core likely formed near 5 GPa, 2100 K and $sim$1 log unit below the iron-w"ustite buffer. Moreover, the Moon is depleted relative to the Earth's mantle in elements with volatilities higher than that of Li, with this volatile loss likely having occurred at low temperatures (1400$pm$100 K), consistent with mass-dependent stable isotope fractionation of moderately volatile elements (e.g., Zn, K, Rb). The identical nucleosynthetic (O, Cr, Ti) and radiogenic (W) isotope compositions of the lunar and terrestrial mantles, strongly suggest the two bodies were made from the same material, rather than from an Earth-like impactor. Rb-Sr in FANs and Lu-Hf and Pb-Pb zircon ages point Moon formation close to $sim$4500 Ma. Taken together, there is no unambiguous geochemical or isotopic evidence for the role of an impactor in the formation of the Moon, implying perfect equilibration between the proto-Earth and Moon-forming material or alternative scenarios for its genesis.
{"title":"Composition, Structure and Origin of the Moon","authors":"Paolo A. Sossi, Miki Nakajima, Amir Khan","doi":"arxiv-2408.16840","DOIUrl":"https://doi.org/arxiv-2408.16840","url":null,"abstract":"Here we critically examine the geophysical and geochemical properties of the\u0000Moon in order to identify the extent to which dynamical scenarios satisfy these\u0000observations. New joint inversions of existing lunar geophysical data (mean\u0000mass, moment of inertia, and tidal response) assuming a laterally- and\u0000vertically homogeneous lunar mantle show that, in all cases, a core with a\u0000radius of 300$pm$20 km ($sim$0.8 to 1.5 % the mass of the Moon) is required.\u0000However, an Earth-like Mg# (0.89) in the lunar mantle results in core densities\u0000(7800$pm$100 kg/m$^3$) consistent with that of Fe-Ni alloy, whereas FeO-rich\u0000compositions (Mg# = 0.80--0.84) require lower densities (6100$pm$800\u0000kg/m$^3$). Geochemically, we use new data on mare basalts to reassess the bulk\u0000composition of the Moon for 70 elements, and show that the lunar core likely\u0000formed near 5 GPa, 2100 K and $sim$1 log unit below the iron-w\"ustite buffer.\u0000Moreover, the Moon is depleted relative to the Earth's mantle in elements with\u0000volatilities higher than that of Li, with this volatile loss likely having\u0000occurred at low temperatures (1400$pm$100 K), consistent with mass-dependent\u0000stable isotope fractionation of moderately volatile elements (e.g., Zn, K, Rb).\u0000The identical nucleosynthetic (O, Cr, Ti) and radiogenic (W) isotope\u0000compositions of the lunar and terrestrial mantles, strongly suggest the two\u0000bodies were made from the same material, rather than from an Earth-like\u0000impactor. Rb-Sr in FANs and Lu-Hf and Pb-Pb zircon ages point Moon formation\u0000close to $sim$4500 Ma. Taken together, there is no unambiguous geochemical or\u0000isotopic evidence for the role of an impactor in the formation of the Moon,\u0000implying perfect equilibration between the proto-Earth and Moon-forming\u0000material or alternative scenarios for its genesis.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Spassiani, S. Gentili, R. Console, M. Murru, M. Taroni, G. Falcone
Short-term earthquake clustering is one of the most important features of seismicity. Clusters are identified using various techniques, generally deterministic and based on spatio-temporal windowing. Conversely, the leading rail in short-term earthquake forecasting has a probabilistic view of clustering, usually based on the Epidemic Type Aftershock Sequence (ETAS) models. In this study we compare seismic clusters, identified by two different deterministic window-based techniques, with the ETAS probabilities associated with any event in the clusters, thus investigating the consistency between deterministic and probabilistic approaches. The comparison is performed by considering, for each event in an identified cluster, the corresponding probability of being independent and the expected number of triggered events according to ETAS. Results show no substantial differences between the cluster identification procedures, and an overall consistency between the identified clusters and the relative events' ETAS probabilities.
{"title":"Reconciling the irreconcilable: window-based versus stochastic declustering algorithms","authors":"I. Spassiani, S. Gentili, R. Console, M. Murru, M. Taroni, G. Falcone","doi":"arxiv-2408.16491","DOIUrl":"https://doi.org/arxiv-2408.16491","url":null,"abstract":"Short-term earthquake clustering is one of the most important features of\u0000seismicity. Clusters are identified using various techniques, generally\u0000deterministic and based on spatio-temporal windowing. Conversely, the leading\u0000rail in short-term earthquake forecasting has a probabilistic view of\u0000clustering, usually based on the Epidemic Type Aftershock Sequence (ETAS)\u0000models. In this study we compare seismic clusters, identified by two different\u0000deterministic window-based techniques, with the ETAS probabilities associated\u0000with any event in the clusters, thus investigating the consistency between\u0000deterministic and probabilistic approaches. The comparison is performed by\u0000considering, for each event in an identified cluster, the corresponding\u0000probability of being independent and the expected number of triggered events\u0000according to ETAS. Results show no substantial differences between the cluster\u0000identification procedures, and an overall consistency between the identified\u0000clusters and the relative events' ETAS probabilities.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The study of meteorites and their microstructures is a topic which spans multiple fields of research, such as meteoritics and materials science. For materials scientists and engineers, the extreme and unusual conditions which these microstructures form allow for insight into materials which would exist at the edge of our thermomechanical processing abilities. One such microstructure found in low-shock event iron meteorites is Neumann bands. These bands are an array of lenticular deformation twins that form throughout the Fe-Ni matrix with numerous intersections, resulting in many high stress and strain regions within the material's surface. The existence of these regions and the shocks that formed them encourage atypical strain accommodating mechanisms and structural changes of the material. However, direct investigation of the deformation twin intersections and the microstructural behaviour in and around these regions has been limited. In this work, investigation of these regions in a Campo del Cielo meteorite fragment, with electron backscatter diffraction (EBSD) and forescatter electron (FSE) imaging, revealed two primary findings: high-intensity pattern doubling mirrored across the {110} band at twin-twin intersection and microband formation across the sample surface, which suggest multilayer twinning and constraint of the crystal structure at points of twin-twin intersection. Microbands were found to form along the {110} plane and in regions near Neumann bands. The simultaneous existence of Neumann bands (microtwins) and microbands is presented here for a BCC material, and it is believed the Neumann band and microbands formed during different types and/or shock events. The presence of both Neumann bands and microbands within a BCC iron meteorite is previously unreported and may be valuable in furthering our understanding of shock deformation within iron-based materials.
对陨石及其微观结构的研究是一个横跨多个研究领域的课题，如陨石学和材料科学。对于材料科学家和工程师来说，这些微观结构所形成的极端和不寻常的条件可以让他们深入了解那些存在于我们热机械加工能力边缘的材料。在低冲击事件铁陨石中发现的一种此类微结构是诺伊曼带。这些条带是在整个铁-镍基体中形成的透镜状变形孪晶阵列，有许多交叉点，从而在材料表面形成许多高应力和高应变区域。这些区域的存在以及形成这些区域的冲击促进了材料的非典型应变容纳机制和结构变化。然而，对这些区域及其周围的变形孪晶交叉和微观结构行为的直接研究一直很有限。在这项工作中，利用电子反向散射衍射（EBSD）和前散射电子（FSE）成像技术对 Campo del Cielo 陨石碎片中的这些区域进行了研究，发现了两个主要发现：孪晶交汇处{110}波段上的高强度图案加倍镜像和整个样品表面的微带形成，这表明在孪晶交汇点存在多层孪晶和晶体结构约束。微带在{110}平面和诺伊曼带附近区域形成。这里介绍的是同时存在诺伊曼带（微孪晶）和微带的 BCC 材料，认为诺伊曼带和微带是在不同类型和/或冲击事件中形成的。在 BCC 铁陨石中同时存在诺伊曼带和微带是以前从未报道过的，这对于我们进一步了解铁基材料的冲击变形可能是有价值的。
{"title":"Microstructural characterization to reveal evidence of shock deformation in a Campo del Cielo meteorite fragment","authors":"Graeme J. Francolini, Thomas B. Britton","doi":"arxiv-2408.16901","DOIUrl":"https://doi.org/arxiv-2408.16901","url":null,"abstract":"The study of meteorites and their microstructures is a topic which spans\u0000multiple fields of research, such as meteoritics and materials science. For\u0000materials scientists and engineers, the extreme and unusual conditions which\u0000these microstructures form allow for insight into materials which would exist\u0000at the edge of our thermomechanical processing abilities. One such\u0000microstructure found in low-shock event iron meteorites is Neumann bands. These\u0000bands are an array of lenticular deformation twins that form throughout the\u0000Fe-Ni matrix with numerous intersections, resulting in many high stress and\u0000strain regions within the material's surface. The existence of these regions\u0000and the shocks that formed them encourage atypical strain accommodating\u0000mechanisms and structural changes of the material. However, direct\u0000investigation of the deformation twin intersections and the microstructural\u0000behaviour in and around these regions has been limited. In this work,\u0000investigation of these regions in a Campo del Cielo meteorite fragment, with\u0000electron backscatter diffraction (EBSD) and forescatter electron (FSE) imaging,\u0000revealed two primary findings: high-intensity pattern doubling mirrored across\u0000the {110} band at twin-twin intersection and microband formation across the\u0000sample surface, which suggest multilayer twinning and constraint of the crystal\u0000structure at points of twin-twin intersection. Microbands were found to form\u0000along the {110} plane and in regions near Neumann bands. The simultaneous\u0000existence of Neumann bands (microtwins) and microbands is presented here for a\u0000BCC material, and it is believed the Neumann band and microbands formed during\u0000different types and/or shock events. The presence of both Neumann bands and\u0000microbands within a BCC iron meteorite is previously unreported and may be\u0000valuable in furthering our understanding of shock deformation within iron-based\u0000materials.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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