Articles | Volume 9, issue 2
https://doi.org/10.5194/se-9-491-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/se-9-491-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
25 Apr 2018
Research article |
| 25 Apr 2018
| 25 Apr 2018
Geomagnetic field declination: from decadal to centennial scales
Venera Dobrica
CORRESPONDING AUTHOR
Institute of Geodynamics, Romanian Academy, Bucharest, Romania
Crisan Demetrescu
Institute of Geodynamics, Romanian Academy, Bucharest, Romania
Mioara Mandea
Centre National d'Etudes Spatiales, Paris, France
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Manuscript not accepted for further review
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This investigation was necessary due to the economical and social importance of the Danube lower basin discharge, taking into account the climate change (greenhouse and solar/geomagnetic activity) impact, as well as few approaches on this issue.
By applying robust statistical methods and rigorously testing of results, new indicators were found to estimate the discharge in the Danube lower basin.
The investigation will be extended with indicators from the climate change models.
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To understand core dynamics, insight from several possible observables is needed. By applying several separation methods, we show spatiotemporal variabilities in the magnetic and gravity fields related to the core dynamics. A 7-year oscillation is found in all conducted analyses. The results in the magnetic field reflect the core processes and the variabilities in the gravity field exhibit new findings that might be an interesting input to build an enhanced model of the Earth’s core.
Anny Cazenave, Julia Pfeffer, Mioara Mandea, and Veronique Dehant
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While a 6-year oscillation has been reported for some time in the motions of the fluid outer core of the Earth, in the magnetic field and in the Earth rotation, novel results indicate that the climate system also oscillates at this 6-year frequency. This strongly suggests the existence of coupling mechanisms affecting the Earth system as a whole, from the deep Earth interior to the surface fluid envelopes.
Mioara Mandea and Eduard Petrovský
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Throughout the International Union of Geodesy and Geophysics' (IUGG's) centennial anniversary, the International Association of Geomagnetism and Aeronomy is holding a series of activities to underline the ground-breaking facts in the area of geomagnetism and aeronomy. Over 100 years, the history of this research is rich, and here we present a short tour through some of the IAGA's major achievements, starting with the scientific landscape before IAGA, through its foundation until the present day.
Roman Sidorov, Anatoly Soloviev, Alexei Gvishiani, Viktor Getmanov, Mioara Mandea, Anatoly Petrukhin, and Igor Yashin
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Decidated to the combined analysis of space weather data (geomagnetic activity, cosmic ray secondaries and ionospheric data) obtained during the September 2017 solar flares and geomagnetic storms, this study is an attempt to construct a technique for circumterrestrial physical data analysis in order to analyze various space weather effects and obtain new mutually supportive information during major space weather events on different phases of geomagnetic storm evolution.
Mioara Mandea and Jean-Louis Le Mouël
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Manuscript not accepted for further review
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Monika Korte and Mioara Mandea
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We investigated characteristics of magnetic anomalies over southern Africa (South Africa, Namibia, and Botswana) and Germany on different scales and also compared them to gravity gradient anomalies. Such anomalies provide information relevant to understanding geological and tectonic structures. Our results indicate a better agreement between anomalies caused by shallow and deeper structures in the southern African area than in the German area.
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A. Khokhlov, J. L. Le Mouël, and M. Mandea
Geosci. Instrum. Method. Data Syst., 2, 1–9, https://doi.org/10.5194/gi-2-1-2013, https://doi.org/10.5194/gi-2-1-2013, 2013
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Evgeniia Martuganova, Manfred Stiller, Ben Norden, Jan Henninges, and Charlotte M. Krawczyk
Solid Earth, 13, 1291–1307, https://doi.org/10.5194/se-13-1291-2022, https://doi.org/10.5194/se-13-1291-2022, 2022
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We demonstrate the applicability of vertical seismic profiling (VSP) acquired using wireline distributed acoustic sensing (DAS) technology for deep geothermal reservoir imaging and characterization. Borehole DAS data provide critical input for seismic interpretation and help assess small-scale geological structures. This case study can be used as a basis for detailed structural exploration of geothermal reservoirs and provide insightful information for geothermal exploration projects.
Brij Singh, Michał Malinowski, Andrzej Górszczyk, Alireza Malehmir, Stefan Buske, Łukasz Sito, and Paul Marsden
Solid Earth, 13, 1065–1085, https://doi.org/10.5194/se-13-1065-2022, https://doi.org/10.5194/se-13-1065-2022, 2022
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Fast depletion of shallower deposits is pushing the mining industry to look for cutting-edge technologies for deep mineral targeting. We demonstrated a joint workflow including two state-of-the-art technologies: full-waveform inversion and reverse time migration. We produced Earth images with significant details which can help with better estimation of areas with high mineralisation, better mine planning and safety measures.
Felix Hloušek, Michal Malinowski, Lena Bräunig, Stefan Buske, Alireza Malehmir, Magdalena Markovic, Lukasz Sito, Paul Marsden, and Emma Bäckström
Solid Earth, 13, 917–934, https://doi.org/10.5194/se-13-917-2022, https://doi.org/10.5194/se-13-917-2022, 2022
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Methods for mineral exploration play an important role within the EU. Exploration must be environmentally friendly, cost effective, and feasible in populated areas. Seismic methods have the potential to deliver detailed images of mineral deposits but suffer from these demands. We show the results for a sparse 3D seismic dataset acquired in Sweden. The 3D depth image allows us to track the known mineralizations beyond the known extent and gives new insights into the geometry of the deposit.
Robert Jackisch, Björn H. Heincke, Robert Zimmermann, Erik V. Sørensen, Markku Pirttijärvi, Moritz Kirsch, Heikki Salmirinne, Stefanie Lode, Urpo Kuronen, and Richard Gloaguen
Solid Earth, 13, 793–825, https://doi.org/10.5194/se-13-793-2022, https://doi.org/10.5194/se-13-793-2022, 2022
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We integrate UAS-based magnetic and multispectral data with legacy exploration data of a Ni–Cu–PGE prospect on Disko Island, West Greenland. The basalt unit has a complex magnetization, and we use a constrained 3D magnetic vector inversion to estimate magnetic properties and spatial dimensions of the target unit. Our 3D modelling reveals a horizontal sheet and a strong remanent magnetization component. We highlight the advantage of UAS use in rugged and remote terrain.
Trond Ryberg, Moritz Kirsch, Christian Haberland, Raimon Tolosana-Delgado, Andrea Viezzoli, and Richard Gloaguen
Solid Earth, 13, 519–533, https://doi.org/10.5194/se-13-519-2022, https://doi.org/10.5194/se-13-519-2022, 2022
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Novel methods for mineral exploration play an important role in future resource exploration. The methods have to be environmentally friendly, socially accepted and cost effective by integrating multidisciplinary methodologies. We investigate the potential of passive, ambient noise tomography combined with 3D airborne electromagnetics for mineral exploration in Geyer, Germany. We show that the combination of the two geophysical data sets has promising potential for future mineral exploration.
Chiara Colombero, Myrto Papadopoulou, Tuomas Kauti, Pietari Skyttä, Emilia Koivisto, Mikko Savolainen, and Laura Valentina Socco
Solid Earth, 13, 417–429, https://doi.org/10.5194/se-13-417-2022, https://doi.org/10.5194/se-13-417-2022, 2022
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Passive-source surface waves may be exploited in mineral exploration for deeper investigations. We propose a semi-automatic workflow for their processing. The geological interpretation of the results obtained at a mineral site (Siilinjärvi phosphorus mine) shows large potentialities and effectiveness of the proposed workflow.
Yueyang Xia, Dirk Klaeschen, Heidrun Kopp, and Michael Schnabel
Solid Earth, 13, 367–392, https://doi.org/10.5194/se-13-367-2022, https://doi.org/10.5194/se-13-367-2022, 2022
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Geological interpretations based on seismic depth images depend on an accurate subsurface velocity model. Reflection tomography is one method to iteratively update a velocity model based on depth error analysis. We used a warping method to estimate closely spaced data-driven depth error displacement fields. The application to a multichannel seismic line across the Sunda subduction zone illustrates the approach which leads to more accurate images of complex geological structures.
Martin Peter Lipus, Felix Schölderle, Thomas Reinsch, Christopher Wollin, Charlotte Krawczyk, Daniela Pfrang, and Kai Zosseder
Solid Earth, 13, 161–176, https://doi.org/10.5194/se-13-161-2022, https://doi.org/10.5194/se-13-161-2022, 2022
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A fiber-optic cable was installed along a freely suspended rod in a deep geothermal well in Munich, Germany. A cold-water injection test was monitored with fiber-optic distributed acoustic and temperature sensing. During injection, we observe vibrational events in the lower part of the well. On the basis of a mechanical model, we conclude that the vibrational events are caused by thermal contraction of the rod. The results illustrate potential artifacts when analyzing downhole acoustic data.
Jean-Baptiste P. Koehl, Craig Magee, and Ingrid M. Anell
Solid Earth, 13, 85–115, https://doi.org/10.5194/se-13-85-2022, https://doi.org/10.5194/se-13-85-2022, 2022
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The present study shows evidence of fault systems (large cracks in the Earth's crust) hundreds to thousands of kilometers long and several kilometers thick extending from northwestern Russia to the northern Norwegian Barents Sea and the Svalbard Archipelago using seismic, magnetic, and gravimetric data. The study suggests that the crust in Svalbard and the Barents Sea was already attached to Norway and Russia at ca. 650–550 Ma, thus challenging existing models.
Andrei Maksymowicz, Daniela Montecinos-Cuadros, Daniel Díaz, María José Segovia, and Tomás Reyes
Solid Earth, 13, 117–136, https://doi.org/10.5194/se-13-117-2022, https://doi.org/10.5194/se-13-117-2022, 2022
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This work analyses the density structure of the continental forearc in the northern segment of the 1960 Mw 9.6 Valdivia earthquake. Results show a segmentation of the continental wedge along and perpendicular to the margin. The extension of the less rigid basement units conforming the marine wedge and Coastal Cordillera domain could modify the process of stress loading during the interseismic periods. This analysis highlights the role of the overriding plate on the seismotectonic process.
Hossein Hassani, Felix Hloušek, Stefan Buske, and Olaf Wallner
Solid Earth, 12, 2703–2715, https://doi.org/10.5194/se-12-2703-2021, https://doi.org/10.5194/se-12-2703-2021, 2021
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Passive seismic imaging methods use natural earthquakes as seismic sources, while in active seismic imaging methods, artificial sources (e.g. explosives) are used to generate seismic waves. We imaged some structures related to a major fault plane through a passive seismic imaging approach using microearthquakes with magnitudes smaller than 0.9 (Mw). These structures have not been illuminated by a previously conducted 3D active seismic survey due to their large dip angles.
Maximilian O. Kottwitz, Anton A. Popov, Steffen Abe, and Boris J. P. Kaus
Solid Earth, 12, 2235–2254, https://doi.org/10.5194/se-12-2235-2021, https://doi.org/10.5194/se-12-2235-2021, 2021
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Upscaling fluid flow in fractured reservoirs is an important practice in subsurface resource utilization. In this study, we first conduct numerical simulations of direct fluid flow at locations where fractures intersect to analyze the arising hydraulic complexities. Next, we develop a model that integrates these effects into larger-scale continuum models of fracture networks to investigate their impact on the upscaling. For intensively fractured systems, these effects become important.
Klaus Regenauer-Lieb, Manman Hu, Christoph Schrank, Xiao Chen, Santiago Peña Clavijo, Ulrich Kelka, Ali Karrech, Oliver Gaede, Tomasz Blach, Hamid Roshan, Antoine B. Jacquey, Piotr Szymczak, and Qingpei Sun
Solid Earth, 12, 1829–1849, https://doi.org/10.5194/se-12-1829-2021, https://doi.org/10.5194/se-12-1829-2021, 2021
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This paper presents a trans-disciplinary approach bridging the gap between observations of instabilities from the molecular scale to the very large scale. We show that all scales communicate via propagation of volumetric deformation waves. Similar phenomena are encountered in quantum optics where wave collisions can release sporadic bursts of light. Ocean waves show a similar phenomenon of rogue waves that seem to come from nowhere. This mechanism is proposed to be the trigger for earthquakes.
Yinshuai Ding and Alireza Malehmir
Solid Earth, 12, 1707–1718, https://doi.org/10.5194/se-12-1707-2021, https://doi.org/10.5194/se-12-1707-2021, 2021
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In this article, we investigate the potential of reverse time migration (RTM) for deep targeting iron oxide deposits and the possible AVO effect that is potentially seen in the common image gathers from this migration algorithm. The results are promising and help to delineate the deposits and host rock structures using a 2D dataset from the Ludvika mines of central Sweden.
Nikita Afonin, Elena Kozlovskaya, Suvi Heinonen, and Stefan Buske
Solid Earth, 12, 1563–1579, https://doi.org/10.5194/se-12-1563-2021, https://doi.org/10.5194/se-12-1563-2021, 2021
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In our study, we show the results of a passive seismic interferometry application for mapping the uppermost crust in the area of active mineral exploration in northern Finland. The obtained velocity models agree well with geological data and complement the results of reflection seismic data interpretation.
Puy Ayarza, José Ramón Martínez Catalán, Ana Martínez García, Juan Alcalde, Juvenal Andrés, José Fernando Simancas, Immaculada Palomeras, David Martí, Irene DeFelipe, Chris Juhlin, and Ramón Carbonell
Solid Earth, 12, 1515–1547, https://doi.org/10.5194/se-12-1515-2021, https://doi.org/10.5194/se-12-1515-2021, 2021
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Vertical incidence seismic profiling on the Iberian Massif images a mid-crustal-scale discontinuity at the top of the reflective lower crust. This feature shows that upper- and lower-crustal reflections merge into it, suggesting that it has often behaved as a detachment. The orogen-scale extension of this discontinuity, present in Gondwanan and Avalonian affinity terranes into the Iberian Massif, demonstrates its relevance, leading us to interpret it as the Conrad discontinuity.
Peter-Lasse Giertzuch, Joseph Doetsch, Alexis Shakas, Mohammadreza Jalali, Bernard Brixel, and Hansruedi Maurer
Solid Earth, 12, 1497–1513, https://doi.org/10.5194/se-12-1497-2021, https://doi.org/10.5194/se-12-1497-2021, 2021
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Two time-lapse borehole ground penetrating radar (GPR) surveys were conducted during saline tracer experiments in weakly fractured crystalline rock with sub-millimeter fractures apertures, targeting electrical conductivity changes. The combination of time-lapse reflection and transmission GPR surveys from different boreholes allowed monitoring the tracer flow and reconstructing the flow path and its temporal evolution in 3D and provided a realistic visualization of the hydrological processes.
Irene Bianchi, Elmer Ruigrok, Anne Obermann, and Edi Kissling
Solid Earth, 12, 1185–1196, https://doi.org/10.5194/se-12-1185-2021, https://doi.org/10.5194/se-12-1185-2021, 2021
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The European Alps formed during collision between the European and Adriatic plates and are one of the most studied orogens for understanding the dynamics of mountain building. In the Eastern Alps, the contact between the colliding plates is still a matter of debate. We have used the records from distant earthquakes to highlight the geometries of the crust–mantle boundary in the Eastern Alpine area; our results suggest a complex and faulted internal crustal structure beneath the higher crests.
Saeid Cheraghi, Alireza Malehmir, Mostafa Naghizadeh, David Snyder, Lucie Mathieu, and Pierre Bedeaux
Solid Earth, 12, 1143–1164, https://doi.org/10.5194/se-12-1143-2021, https://doi.org/10.5194/se-12-1143-2021, 2021
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High-resolution seismic profiles in 2D are acquired in the north and south of the Chibougamau area, Quebec, Canada located in the northeast of the Abitibi Greenstone belt. The area mostly includes volcanic rocks, and both profiles cross over several fault zones. The seismic method is acquired to image the subsurface down to depth of 12 km. The main aim of this study is to image major fault zones and the geological formations connected to those faults to investigate metal endowment in the area.
Jean-Baptiste P. Koehl
Solid Earth, 12, 1025–1049, https://doi.org/10.5194/se-12-1025-2021, https://doi.org/10.5194/se-12-1025-2021, 2021
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By using seismic data and fieldwork, this contribution shows that soft, coal-rich sedimentary rocks absorbed most of early Cenozoic, Eurekan, contractional deformation in central Spitsbergen, thus suggesting that no contractional deformation event is needed in the Late Devonian to explain the deformation differences among late Paleozoic sedimentary rocks. It also shows that the Billefjorden Fault Zone, a major crack in the Earth's crust in Svalbard, is probably segmented.
Gilda Currenti, Philippe Jousset, Rosalba Napoli, Charlotte Krawczyk, and Michael Weber
Solid Earth, 12, 993–1003, https://doi.org/10.5194/se-12-993-2021, https://doi.org/10.5194/se-12-993-2021, 2021
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We investigate the capability of distributed acoustic sensing (DAS) to record dynamic strain changes related to Etna volcano activity in 2019. To validate the DAS measurements, we compute strain estimates from seismic signals recorded by a dense broadband array. A general good agreement is found between array-derived strain and DAS measurements along the fibre optic cable. Localised short wavelength discrepancies highlight small-scale structural heterogeneities in the investigated area.
Klaus Regenauer-Lieb, Manman Hu, Christoph Schrank, Xiao Chen, Santiago Peña Clavijo, Ulrich Kelka, Ali Karrech, Oliver Gaede, Tomasz Blach, Hamid Roshan, and Antoine B. Jacquey
Solid Earth, 12, 869–883, https://doi.org/10.5194/se-12-869-2021, https://doi.org/10.5194/se-12-869-2021, 2021
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In this paper we expand on a recent discovery of slow cross-diffusion hydromechanical waves cast into a new concise reaction–diffusion equation for THMC coupling. If waves are excited through the THMC reaction terms unbounded reactions can be captured by inclusion of statistical information from the lower scale through nonlocal reaction–diffusion equations. These cross-diffusion coefficients regularize extreme earthquake-like events (rogue waves) through a new form of quasi-soliton wave.
Christian Emile Nyaban, Théophile Ndougsa-Mbarga, Marcelin Bikoro-Bi-Alou, Stella Amina Manekeng Tadjouteu, and Stephane Patrick Assembe
Solid Earth, 12, 785–800, https://doi.org/10.5194/se-12-785-2021, https://doi.org/10.5194/se-12-785-2021, 2021
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A multi-scale analysis of aeromagnetic data combining tilt derivative, Euler deconvolution, upward continuation, and 2.75D modelling was applied over Cameroon between the latitudes 5°30'–6° N and the longitudes 13°30'–14°45' E. Major families of faults oriented ENE–WSW, E–W, NW–SE, and N–S with a NE–SW prevalence were mapped. Depths of interpreted faults range from 1000 to 3400 m, mylonitic veins were identified, and 2.75D modelling revealed fault depths greater than 1200 m.
Jennifer E. Cunningham, Nestor Cardozo, Chris Townsend, and Richard H. T. Callow
Solid Earth, 12, 741–764, https://doi.org/10.5194/se-12-741-2021, https://doi.org/10.5194/se-12-741-2021, 2021
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This work investigates the impact of commonly used seismic interpretation methods on the analysis of faults. Fault analysis refers to fault length, displacement, and the impact these factors have on geological modelling and hydrocarbon volume calculation workflows. This research was conducted to give geoscientists a better understanding of the importance of interpretation methods and the impact of unsuitable methology on geological analyses.
Jan Henninges, Evgeniia Martuganova, Manfred Stiller, Ben Norden, and Charlotte M. Krawczyk
Solid Earth, 12, 521–537, https://doi.org/10.5194/se-12-521-2021, https://doi.org/10.5194/se-12-521-2021, 2021
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We performed a seismic survey in two 4.3 km deep geothermal research wells using the novel method of distributed acoustic sensing and wireline cables. The characteristics of the acquired data, methods for data processing and quality improvement, and interpretations on the geometry and structure of the sedimentary and volcanic reservoir rocks are presented. The method enables measurements at high temperatures and reduced cost compared to conventional sensors.
Matthias Bücker, Adrián Flores Orozco, Jakob Gallistl, Matthias Steiner, Lukas Aigner, Johannes Hoppenbrock, Ruth Glebe, Wendy Morales Barrera, Carlos Pita de la Paz, César Emilio García García, José Alberto Razo Pérez, Johannes Buckel, Andreas Hördt, Antje Schwalb, and Liseth Pérez
Solid Earth, 12, 439–461, https://doi.org/10.5194/se-12-439-2021, https://doi.org/10.5194/se-12-439-2021, 2021
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We use seismic, electromagnetic, and geoelectrical methods to assess sediment thickness and lake-bottom geology of two karst lakes. An unexpected drainage event provided us with the unusual opportunity to compare water-borne measurements with measurements carried out on the dry lake floor. The resulting data set does not only provide insight into the specific lake-bottom geology of the studied lakes but also evidences the potential and limitations of the employed field methods.
Alireza Malehmir, Magdalena Markovic, Paul Marsden, Alba Gil, Stefan Buske, Lukasz Sito, Emma Bäckström, Martiya Sadeghi, and Stefan Luth
Solid Earth, 12, 483–502, https://doi.org/10.5194/se-12-483-2021, https://doi.org/10.5194/se-12-483-2021, 2021
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A smooth transition toward decarbonization demands access to more minerals of critical importance. Europe has a good geology for many of these mineral deposits, but at a depth requiring sensitive, environmentally friendly, and cost-effective methods for their exploration. In this context, we present a sparse 3D seismic dataset that allowed identification of potential iron oxide resources at depth and helped to characterise key geological structures and a historical tailing in central Sweden.
Alba Zappone, Antonio Pio Rinaldi, Melchior Grab, Quinn C. Wenning, Clément Roques, Claudio Madonna, Anne C. Obermann, Stefano M. Bernasconi, Matthias S. Brennwald, Rolf Kipfer, Florian Soom, Paul Cook, Yves Guglielmi, Christophe Nussbaum, Domenico Giardini, Marco Mazzotti, and Stefan Wiemer
Solid Earth, 12, 319–343, https://doi.org/10.5194/se-12-319-2021, https://doi.org/10.5194/se-12-319-2021, 2021
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The success of the geological storage of carbon dioxide is linked to the availability at depth of a capable reservoir and an impermeable caprock. The sealing capacity of the caprock is a key parameter for long-term CO2 containment. Faults crosscutting the caprock might represent preferential pathways for CO2 to escape. A decameter-scale experiment on injection in a fault, monitored by an integrated network of multiparamerter sensors, sheds light on the mobility of fluids within the fault.
Juvenal Andrés, Puy Ayarza, Martin Schimmel, Imma Palomeras, Mario Ruiz, and Ramon Carbonell
Solid Earth, 11, 2499–2513, https://doi.org/10.5194/se-11-2499-2020, https://doi.org/10.5194/se-11-2499-2020, 2020
Yi Zhang, Xinglin Lei, Tsutomu Hashimoto, and Ziqiu Xue
Solid Earth, 11, 2487–2497, https://doi.org/10.5194/se-11-2487-2020, https://doi.org/10.5194/se-11-2487-2020, 2020
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Spatially continuous strain responses in two monitoring wells induced by a well-drilling process were monitored using high-resolution fiber-optic distributed strain sensing (DSS). The modeling results suggest that the strain polarities and magnitudes along the wellbores may be indicative of the layered-permeability structure or heterogeneous formation damage. The performance and value of DSS as a novel hydrogeophysical tool for in situ subsurface monitoring are emphasized.
Benjamin Schwarz and Charlotte M. Krawczyk
Solid Earth, 11, 1891–1907, https://doi.org/10.5194/se-11-1891-2020, https://doi.org/10.5194/se-11-1891-2020, 2020
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Intricate fault and fracture networks cut through the upper crust, and their detailed delineation and characterization play an important role in the Earth sciences. While conventional geophysical sounding techniques only provide indirect means of detection, we present scale-spanning field data examples, in which coherent diffraction imaging – a framework inspired by optics and visual perception – enables the direct imaging of these crustal features at an unprecedented spatial resolution.
Laurent Guillou-Frottier, Hugo Duwiquet, Gaëtan Launay, Audrey Taillefer, Vincent Roche, and Gaétan Link
Solid Earth, 11, 1571–1595, https://doi.org/10.5194/se-11-1571-2020, https://doi.org/10.5194/se-11-1571-2020, 2020
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In the first kilometers of the subsurface, temperature anomalies due to heat conduction rarely exceed 20–30°C. However, when deep hot fluids in the shallow crust flow upwards, for example through permeable fault zones, hydrothermal convection can form high-temperature geothermal reservoirs. Numerical modeling of hydrothermal convection shows that vertical fault zones may host funnel-shaped, kilometer-sized geothermal reservoirs whose exploitation would not need drilling at depths below 2–3 km.
Joseph Doetsch, Hannes Krietsch, Cedric Schmelzbach, Mohammadreza Jalali, Valentin Gischig, Linus Villiger, Florian Amann, and Hansruedi Maurer
Solid Earth, 11, 1441–1455, https://doi.org/10.5194/se-11-1441-2020, https://doi.org/10.5194/se-11-1441-2020, 2020
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Short summary
By analyzing frequency constituents of declination secular variation at inter-decadal and sub-centennial timescales from geomagnetic observatories with data longer than 1 century and several historical data sets, we suggest that the geomagnetic jerk concept should be considered as a more general notion, namely the evolution of the secular variation as a result of the superposition of two (or more) constituents describing the effects of processes in the Earth’s core at two (or more) timescales.
By analyzing frequency constituents of declination secular variation at inter-decadal and...
