| 1. |
- Ayarza, Puy, et al.
(författare)
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Evolution of the Iberian Massif as deduced from its crustal thickness and geometry of a mid-crustal (Conrad) discontinuity
- 2021
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Ingår i: Solid Earth. - : Copernicus Publications. - 1869-9510 .- 1869-9529. ; 12:7, s. 1515-1547
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Tidskriftsartikel (refereegranskat)abstract
- Y Normal incidence seismic data provide the best images of the crust and lithosphere. When properly designed and continuous, these sections greatly contribute to understanding the geometry of orogens and, along with surface geology, unraveling their evolution. In this paper we present the most complete transect, to date, of the Iberian Massif, the westernmost exposure of the European Variscides. Despite the heterogeneity of the dataset, acquired during the last 30 years, the images resulting from reprocessing the data with a homogeneous workflow allow us to clearly define the crustal thickness and its internal architecture. The Iberian Massif crust, formed by the amalgamation of continental pieces belonging to Gondwana and Laurussia (Avalonian margin), is well structured in the upper and lower crust. A conspicuous mid-crustal discontinuity is clearly defined by the top of the reflective lower crust and by the asymptotic geometry of reflections that merge into it, suggesting that it has often acted as a detachment. The geometry and position of this discontinuity can give us insights into the evolution of the orogen (i.e., of the magnitude of compression and the effects and extent of later-Variscan gravitational collapse). Moreover, the limited thickness of the lower crust below, in central and northwestern Iberia, might have constrained the response of the Iberian microplate to Alpine shortening. Here, this discontinuity, featuring a Vp (P-wave velocity) increase, is observed as an orogen-scale boundary with characteristics compatible with those of the globally debated Conrad discontinuity.
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| 2. |
- Carraminana, Albert, et al.
(författare)
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Rationale and Study Design for an Individualized Perioperative Open Lung Ventilatory Strategy in Patients on One-Lung Ventilation (iPROVE-OLV)
- 2019
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Ingår i: Journal of Cardiothoracic and Vascular Anesthesia. - : W B SAUNDERS CO-ELSEVIER INC. - 1053-0770 .- 1532-8422. ; 33:9, s. 2492-2502
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of this clinical trial is to examine whether it is possible to reduce postoperative complications using an individualized perioperative ventilatory strategy versus using a standard lung-protective ventilation strategy in patients scheduled for thoracic surgery requiring one-lung ventilation. Design: International, multicenter, prospective, randomized controlled clinical trial. Setting: A network of university hospitals. Participants: The study comprises 1,380 patients scheduled for thoracic surgery. Interventions: The individualized group will receive intraoperative recruitment maneuvers followed by individualized positive end-expiratory pressure (open lung approach) during the intraoperative period plus postoperative ventilatory support with high-flow nasal cannula, whereas the control group will be managed with conventional lung-protective ventilation. Measurements and Main Results: Individual and total number of postoperative complications, including atelectasis, pneumothorax, pleural effusion, pneumonia, acute lung injury; unplanned readmission and reintubation; length of stay and death in the critical care unit and in the hospital will be analyzed for both groups. The authors hypothesize that the intraoperative application of an open lung approach followed by an individual indication of high-flow nasal cannula in the postoperative period will reduce pulmonary complications and length of hospital stay in high-risk surgical patients. (C) 2019 Published by Elsevier Inc.
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| 3. |
- Alcalde, Juan, et al.
(författare)
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3D geological characterization of the Hontomin CO2 storage site, Spain : Multidisciplinary approach from seismic, well-log and regional data
- 2014
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Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951 .- 1879-3266. ; 627, s. 6-25
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Tidskriftsartikel (refereegranskat)abstract
- The first Spanish Technological Development plant for CO2 storage is currently under development in Hontomin (Spain), in a fractured carbonate reservoir. The subsurface 3D geological structures of the Hontomin site were interpreted using well-log and 3D seismic reflection data. A shallow low velocity zone affects the wave propagation and decreases the coherency of the underlying seismic reflections, deteriorating the quality of the seismic data, and thus preventing a straightforward seismic interpretation. In order to provide a fully constrained model, a geologically supervised interpretation was carried out. In particular, a conceptual geological model was derived from an exhaustive well-logging analysis. This conceptual model was then improved throughout a detailed seismic facies analysis on selected seismic sections crossing the seismic wells and in consistency with the regional geology, leading to the interpretation of the entire 3D seismic volume. This procedure allowed characterizing nine main geological levels and four main fault sets. Thus, the stratigraphic sequence of the area and the geometries of the subsurface structures were defined. The resulting depth-converted 3D geological model allowed us to estimate a maximum CO2 storage capacity of 5.85 Mt. This work provides a 3D geological model of the Hontomin subsurface, which is a challenging case study of CO2 storage in a complex fractured carbonate reservoir.
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| 4. |
- Bergman, Björn, 1973-
(författare)
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High-Resolution Seismics Methods Applied to Till Covered Hard Rock Environments
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reflection seismic and seismic tomography methods can be used to image the upper kilometer of hard bedrock and the loose unconsolidated sediments covering it. Developments of these two methods and their application, as well as identifying issues concerning their usage, are the main focus of the thesis. Data used for this development were acquired at three different sites in Sweden, in Forsmark 140 km north of Stockholm, in the Oskarshamn area in southern Sweden, and in the northern part of the Siljan Ring impact crater area.The reflection seismic data were acquired with long source-receiver offsets relative to some of the targeted depths to be imaged. In the initial processing standard steps were applied, but the uppermost part of the sections were not always clear. The longer offsets imply that pre-stack migration is necessary in order to image the uppermost bedrock as clearly as possible. Careful choice of filters and velocity functions improve the pre-stack migrated image, allowing better correlation with near-surface geological information.The seismic tomography method has been enhanced to calculate, simultaneously with the velocity inversion, optimal corrections to the picked first break travel times in order to compensate for the delays due to the seismic waves passing through the loose sediments covering the bedrock.The reflection seismic processing used in this thesis has produced high-quality images of the upper kilometers, and in one example from the Forsmark site, the image of the uppermost 250 meters of the bedrock has been improved. The three-dimensional orientation of reflections has been determined at the Oskarshamn site. Correlation with borehole data shows that many of these reflections originate from fracture zones.The developed seismic tomography method produces high-detail velocity models for the site in the Siljan impact area and for the Forsmark site. In Forsmark, detailed estimates of the bedrock topography were calculated with the use of the developed tomography method.
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| 5. |
- Cruz, Raquel, et al.
(författare)
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Novel genes and sex differences in COVID-19 severity
- 2022
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Ingår i: Human Molecular Genetics. - : Oxford University Press. - 0964-6906 .- 1460-2083. ; 31:22, s. 3789-3806
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Tidskriftsartikel (refereegranskat)abstract
- Here, we describe the results of a genome-wide study conducted in 11 939 coronavirus disease 2019 (COVID-19) positive cases with an extensive clinical information that were recruited from 34 hospitals across Spain (SCOURGE consortium). In sex-disaggregated genome-wide association studies for COVID-19 hospitalization, genome-wide significance (P < 5 × 10−8) was crossed for variants in 3p21.31 and 21q22.11 loci only among males (P = 1.3 × 10−22 and P = 8.1 × 10−12, respectively), and for variants in 9q21.32 near TLE1 only among females (P = 4.4 × 10−8). In a second phase, results were combined with an independent Spanish cohort (1598 COVID-19 cases and 1068 population controls), revealing in the overall analysis two novel risk loci in 9p13.3 and 19q13.12, with fine-mapping prioritized variants functionally associated with AQP3 (P = 2.7 × 10−8) and ARHGAP33 (P = 1.3 × 10−8), respectively. The meta-analysis of both phases with four European studies stratified by sex from the Host Genetics Initiative (HGI) confirmed the association of the 3p21.31 and 21q22.11 loci predominantly in males and replicated a recently reported variant in 11p13 (ELF5, P = 4.1 × 10−8). Six of the COVID-19 HGI discovered loci were replicated and an HGI-based genetic risk score predicted the severity strata in SCOURGE. We also found more SNP-heritability and larger heritability differences by age (<60 or ≥60 years) among males than among females. Parallel genome-wide screening of inbreeding depression in SCOURGE also showed an effect of homozygosity in COVID-19 hospitalization and severity and this effect was stronger among older males. In summary, new candidate genes for COVID-19 severity and evidence supporting genetic disparities among sexes are provided.
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| 6. |
- DeFelipe, Irene, et al.
(författare)
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Reassessing the lithosphere : SeisDARE, an open-access seismic data repository
- 2021
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Ingår i: Earth System Science Data. - : Copernicus Publications. - 1866-3508 .- 1866-3516. ; 13:3, s. 1053-1071
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Tidskriftsartikel (refereegranskat)abstract
- Seismic reflection data (normal incidence and wide angle) are unique assets for solid Earth sciences as they provide critical information about the physical properties and structure of the lithosphere as well as about the shallow subsurface for exploration purposes. The resolution of these seismic data is highly appreciated; however they are logistically complex and expensive to acquire, and their geographical coverage is limited. Therefore, it is essential to make the most of the data that have already been acquired. The collation and dissemination of seismic open-access data are then key to promote accurate and innovative research and to enhance new interpretations of legacy data. This work presents the Seismic DAta REpository (SeisDARE), which is, to our knowledge, one of the first comprehensive open-access online databases that stores seismic data registered with a permanent identifier (DOI). The datasets included here are openly accessible online and guarantee the FAIR (findable, accessible, interoperable, reusable) principles of data management, granting the inclusion of each dataset in a statistics referencing database so its impact can be measured. SeisDARE includes seismic data acquired in the last 4 decades in the Iberian Peninsula and Morocco. These areas have attracted the attention of international researchers in the fields of geology and geophysics due to the exceptional outcrops of the Variscan and Alpine orogens and wide foreland basins, the crustal structure of the offshore margins that resulted from a complex plate kinematic evolution, and the vast quantities of natural resources contained within. This database has been built thanks to a network of national and international institutions, promoting a multidisciplinary research and is open for international data exchange and collaborations. As part of this international collaboration, and as a model for inclusion of other global seismic datasets, SeisDARE also hosts seismic data acquired in Hardeman County, Texas (USA), within the COCORP project (Consortium for Continental Reflection Profiling). SeisDARE aims to make easily accessible old and recently acquired seismic data and to establish a framework for future seismic data management plans. SeisDARE is freely available at https://digital.csic.es/handle/10261/101879 (a detailed list of the datasets can be found in Table 1), bringing endless research and teaching opportunities to the scientific, industrial, and educational communities.
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| 7. |
- Ferrando, Carlos, et al.
(författare)
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Effects of oxygen on post-surgical infections during an individualised perioperative open-lung ventilatory strategy : a randomised controlled trial
- 2020
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Ingår i: British Journal of Anaesthesia. - : ELSEVIER SCI LTD. - 0007-0912 .- 1471-6771. ; 124:1, s. 110-120
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Tidskriftsartikel (refereegranskat)abstract
- Background: We aimed to examine whether using a high fraction of inspired oxygen (FIO2) in the context of an individualised intra- and postoperative open-lung ventilation approach could decrease surgical site infection (SSI) in patients scheduled for abdominal surgery. Methods: We performed a multicentre, randomised controlled clinical trial in a network of 21 university hospitals from June 6, 2017 to July 19, 2018. Patients undergoing abdominal surgery were randomly assigned to receive a high (0.80) or conventional (0.3) FIO2 during the intraoperative period and during the first 3 postoperative hours. All patients were mechanically ventilated with an open-lung strategy, which included recruitment manoeuvres and individualised positive end-expiratory pressure for the best respiratory-system compliance, and individualised continuous postoperative airway pressure for adequate peripheral oxyhaemoglobin saturation. The primary outcome was the prevalence of SSI within the first 7 postoperative days. The secondary outcomes were composites of systemic complications, length of intensive care and hospital stay, and 6-month mortality. Results: We enrolled 740 subjects: 371 in the high FIO2 group and 369 in the low FIO2 group. Data from 717 subjects were available for final analysis. The rate of SSI during the first postoperative week did not differ between high (8.9%) and low (9.4%) FIO2 groups (relative risk [RR]: 0.94; 95% confidence interval [CI]: 0.59-1.50; P=0.90]). Secondary outcomes, such as atelectasis (7.7% vs 9.8%; RR: 0.77; 95% CI: 0.48-1.25; P=0.38) and myocardial ischaemia (0.6% [n=2] vs 0% [n=0]; P=0.47) did not differ between groups. Conclusions: An oxygenation strategy using high FIO2 compared with conventional FIO2 did not reduce postoperative SSIs in abdominal surgery. No differences in secondary outcomes or adverse events were found.
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| 8. |
- Gil de la Iglesia, Alba, et al.
(författare)
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3D reflection seismic imaging of the Zinkgruvan mineral-bearing structures in the south-eastern Bergslagen mineral district (Sweden)
- 2023
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Ingår i: Geophysical Prospecting. - : John Wiley & Sons. - 0016-8025 .- 1365-2478. ; 71:7, s. 1132-1151
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Tidskriftsartikel (refereegranskat)abstract
- Mineral exploration is facing greater challenges nowadays because of the increasing demand for raw materials and the lesser chance of finding large deposits at shallow depths. To be efficient and address new exploration challenges, high-resolution and sensitive methods that are cost-effective and environmentally friendly are required. In this work, we present the results of a sparse 3D seismic survey that was conducted in the Zinkgruvan mining area, in the Bergslagen mineral district of central Sweden. The survey covers an area of 10.5 km2 for deep targeting of massive sulphides in a polyphasic tectonic setting. A total of 1311 receivers and 950 shot points in a fixed 3D geometry setup were employed for the survey. Nine 2D profiles and a smaller 3D mesh were used. Shots were generated at every 10 m, and receivers were placed at every 10-20 m, along the 2D profiles, and 40-80 m in the mesh area. An analysis of the seismic fold coverage at depth was used to determine the potential resolving power of this sparse 3D setup. The data processing had to account for cultural noise from the operating mine and strong source-generated surface waves, which were attenuated during both pre- and post-stack processing steps. The processing workflow employed a combination of 2D and 3D refraction static corrections, and post-stack FK filters along inlines and crosslines. The resulting 3D seismic volume is correlated with downhole data (density and P-wave, acoustic impedance, reflection coefficient), synthetic seismograms, surface geology and a 3D model of mineral-bearing horizons in order to suggest new exploration targets at depth. The overall geological architecture at Zinkgruvan is interpreted as two EW overturn folds, an antiform and a synform, affected by later NS-trending folding. Two strong sets of shallow reflections, associated with the Zn-Pb mineralization, are located at the hinge of an EW-trending antiform, while a strong set of reflections, associated with the main mineralization, is located at the overturned apex of the EW synform. The NS Knalla fault that crosses the study area terminates the continuation of the mineral-bearing deposits at depth towards the west, a conclusion solely based on the reflectivity character of the seismic volume. This study illustrates that sparse 3D data acquisition, while it has its own challenges, can be a suitable replacement for 2D profiles while line cutting, and environmental footprints can totally be avoided.
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| 9. |
- Gil de la Iglesia, Alba, et al.
(författare)
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Reflection seismic imaging to unravel subsurface geological structures of the Zinkgruvan mining area, central Sweden
- 2021
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Ingår i: Ore Geology Reviews. - : Elsevier. - 0169-1368 .- 1872-7360. ; 137
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Tidskriftsartikel (refereegranskat)abstract
- The Zinkgruvan mining area is located on the south-eastern part of the Bergslagen district, one of the three major mineral producing regions in Sweden. In this study, we present the results from three (P1, P2 and P8) reflection seismic profiles each approximately 3000 m-long crossing the Zinkgruvan Zn-Pb-Ag-(Cu) mining area. P1 was acquired using cabled geophones with 10 m receiver and source interval and crossed major geological features. The other two profiles (P2 and P8) were acquired by wireless recorders with 20 m receiver and 10 m source interval and ran perpendicular to P1. Through a special data processing workflow adapted to this dataset, good quality seismic sections were obtained along these profiles, although a high noise level due to high voltage electric power lines was present. The interpretations were constrained by (1) seismic P-wave velocity and density data from a series of downhole logging measurements, (2) 3D forward reflection traveltime modelling in both pre- and post-stack domains, and (3) other geophysical and geological observations available from the site. Despite the notably complex geology, the processed seismic sections clearly reveal a series of horizontal to gently dipping reflections associated with known geological formations. Results indicate that most structures and lithological contacts dip or plunge to the northeast, including the targeted Zinkgruvan Formation. The results from this seismic survey are encouraging regarding the potential of the seismic method for base-metal exploration in Sweden and in particular in the Bergslagen district. It shows the high resolving power of the reflection seismic methods for imaging complex geological structures in a cost-effective and environmentally-friendly way.
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| 10. |
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| 11. |
- Roberts, Roland, et al.
(författare)
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Deep Seismic Sounding Data
- 2017
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Rapport (populärvet., debatt m.m.)abstract
- This document is an interim report within a work package of the SERA project. The document lists a considerable number of previous Deep Seismic Sounding (DSS) projects, where data is available in some form. DSS projects are large scale, logistically complex, and there can be some problems in obtaining formal permission to use the very large seismic sources which may be necessary to be able to successfully record seismic signals penetrating to the relevant depths and distances. This implies that in some cases it would be very difficult to repeat the projects, or conduct a similar project along the same recording profile. This means that even older data can be potentially very valuable, and not all such data is available in modern, digital form (e.g. time series), and some metadata descriptions may be complicated or incomplete.In the text below, we discuss what is meant by DSS data; some of the complications related to this type of data, metadata, different forms of data, and some common types of derived (processed data) which exist. We also present information on a considerable number of DSS projects related to the European area, and list some (but far from all) relevant publications. Note that the term “database” is used in AERA. For DSS data, much data is available in well-structured and maintained digital databases, some is available in digital form only as images of seismic sections, and some data exists only in analogue form e.g. as plotted seismic sections. We consider all such types of data to be relevant, and include them in the “database” concept, as discussed below.
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| 12. |
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| 13. |
- Schmelzbach, Cedric, et al.
(författare)
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P- and SV-velocity structure of the South Portuguese Zone fold-and-thrust belt, SW Iberia, from traveltime tomography
- 2008
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Ingår i: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 175:2, s. 689-712
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Tidskriftsartikel (refereegranskat)abstract
- Imaging the architecture of the shallow crust of the South Portuguese Zone fold-and-thrust belt is essential to extend surface mapped geological information to depth and to help in developing models of the ore-bearing Iberian Pyrite Belt part of the Variscan orogeny. The recently acquired IBERSEIS seismic-reflection data set provides, for the first time, detailed images of the entire crust, but source-generated noise masks the earliest reflections and limits the shallowest observed signals to depths >500m. We inverted P- and SV first-arrival traveltimes for the smoothest minimum-structure velocity models, imaging the shallowest few hundreds of metres along four in total ~60-km-long profiles. A comparison of a 2-D and 2.5-D (3-D forward and 2-D inverse problem) crooked-line inversion scheme revealed that the crooked-line geometry has a negligible effect on the final images. Resolution of the final preferred models was assessed on the basis of an extensive series of checkerboard tests, showing a slightly lower resolution capability of the SV-data due to greater data uncertainty, fewer number of picks and more limited source-receiver offsets compared with the P-data. The preferred final models compare favourably with the mapped surface geology, showing relatively high and uniform velocities (>5.25kms-1) for the flysch group in the southern part of the investigation area. Low velocities (~4.5kms-1) are found for the `La Puebla de Guzman antiform' in the centre of the investigation area, where the phyllite-quartzite group is exposed. Velocities fluctuate the most along the northernmost ~20km. Velocity variations reflect more the state of tectonic deformation than being directly correlated with the mapped lithologies. Based on a comparison with coincident seismic-reflection data along the southern half of the area, we suggest that two areas of low to intermediate ratios (~1.85-1.9) correspond to occurrences of thick and less deformed flysch-group units, whereas high ratios (~1.95) are interpreted to indicate increased porosity due to intense fracturing.
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| 14. |
- Schmelzbach, Cedric, et al.
(författare)
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Prestack and poststack migration of crooked-line seismic reflection data : A case study from the South Portuguese Zone fold belt, southwestern Iberia
- 2007
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Ingår i: Geophysics. - : Society of Exploration Geophysicists. - 0016-8033 .- 1942-2156. ; 72:2, s. B9-B18
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Tidskriftsartikel (refereegranskat)abstract
- Crooked-line 2D seismic reflection survey geometries violate underlying assumptions of 2D imaging routines, affecting our ability to resolve the subsurface reliably. We compare three crooked-line imaging schemes involving prestack and poststack time migration using the 2D IBERSEIS deep seismic reflection profile running over the South Portuguese Zone thrust-and-fold belt to obtain crisp high-resolution images of the shallow crust. The crust is characterized by a complex subsurface geometry with conflicting dips of up to 50°. In summary, the three schemes are (1) normal-moveout (NMO) corrections, dip-moveout (DMO) corrections, common-midpoint (CMP) stacking, CMP projection, and poststack time migration; (2) NMO corrections, DMO corrections, CMP projection, zero-offset time migration of the common-offset gathers, and CMP stacking; (3) CMP projection, prestack time migration in the common-offset domain, and CMP stacking. An essential element of all three schemes is a CMP projection routine, projecting the CMPs first binned along individual segments for preprocessing onto one straight line, which is parallel to the general dip direction of the subsurface structures. After CMP projection, the data satisfy the straight-line assumption of 2D imaging routines more closely. We observe that the prestack time-migration scheme yields comparable or more coherent synthetic and field-data images than the other two DMO-based schemes along the parts of the profile where the acquisition overall follows a straight line. However, the schemes involving DMO corrections are less plagued by migration artifacts than the prestack time-migration scheme along profile parts where the acquisition line is crooked. In particular, prominent migration artifacts on the prestack migrated synthetic data can be related to significant variations in source-receiver azimuths for which 2D prestack migration cannot account. Thus, the processing scheme including DMO corrections, CMP projection, and zero-offset migration of common-offset gathers offers a reliable and effective alternative to prestack migration for crooked-line 2D seismic reflection processing.
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| 15. |
- Schmelzbach, Cedric, et al.
(författare)
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Seismic-reflection imaging over the South Portuguese Zone fold-and-thrust belt
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:B8, s. B08301-
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Tidskriftsartikel (refereegranskat)abstract
- We reprocessed an ∼35-km-long part of the IBESREIS seismic reflection profile which runs over the Iberian Pyrite Belt section of the South Portuguese Zone, SW Iberia, with the goal to image the upper crust (<15-km depth). The applied processing sequence enhanced numerous prominent reflections and diffraction patterns within the uppermost 5-s travel time relative to high-amplitude source-generated noise. A complex subsurface characterized by conflicting dips and a survey following winding roads require a crooked-line prestack migration scheme for coherent imaging. To interpret sources of diffracted energy, we additionally employed a diffraction imaging scheme which enhances diffractions at the expense of reflections.The final seismic images show south-vergent imbricate fold-and-thrust tectonics, documenting the contractive deformation that the South Portuguese Zone experienced during the Variscan Orogeny. Based on surface geological information, we correlate a low reflective unit with the shallow Upper Carboniferous Flysch Group, a highly reflective unit ranging in depth from 2 to 4 km with the Middle Carboniferous Volcano–Sedimentary Complex Group, which hosts massive sulfide deposits, and a moderately reflective unit with the Upper Devonian Phyllite–Quartzite Group. Below these units, another low-reflective facies is present, which may represent older Paleozoic metasediments. In addition, the seismic and diffraction images reveal bands of high reflectivity and distinct diffraction patterns that were interpreted as extensive layered mafic intrusions. These proposed mafic bodies may be related to the same event that triggered a huge hydrothermal activity assumed in Early Carbonifereous times.
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| 16. |
- Sharifi Brojerdi, Fatemeh
(författare)
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Analysis of Seismic Data Acquired at the Forsmark Site for Storage of Spent Nuclear Fuel, Central Sweden
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Forsmark area, the main study area in this thesis, is located about 140 km north of Stockholm, central Sweden. It belongs to the Paleoproterozoic Svecokarelian orogen and contains several major ductile and brittle deformation zones including the Forsmark, Eckarfjärden and Singö zones. The bedrock between these zones, in general is less deformed and considered suitable for a nuclear waste repository. While several site investigations have already been carried out in the area, this thesis focuses primarily on (i) re-processing some of the existing reflection seismic lines to improve imaging of deeper structures, (ii) acquiring and processing high-resolution reflection and refraction data for better characterization of the near surface geology for the planning of a new access ramp, (iii) studying possible seismic anisotropy from active sources recorded onto sparse three-component receivers and multi-offset-azimuth vertical seismic profiling data (VSP). Reflection seismic surveys are an important component of these investigations. The re-processing helped in improving the deeper parts (1-5 km) of the seismic images and allowing three major deeper reflections to be better characterized, one of which is sub-horizontal while the other two are dipping moderately. These reflections were attributed to originate from either dolerite sills or brittle fault systems. First break traveltime tomography allowed delineating an undulating bedrock-surface topography, which is typical in the Forsmark area. Shallow reflections imaged in 3D, thanks to the acquisition design were compared with existing borehole data and explained by fractured or weak zones in the bedrock. The analysis of seismic anisotropy indicates the presence of shear-wave splitting due to transverse isotropy with a vertical symmetry axis in the uppermost hundreds of meters of crust. Open fractures and joints were interpreted to be responsible for the large delays observed between the transverse and radial components of the shear-wave arrivals, both on surface and VSP data.
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