Stratigraphic control on damage zone width in faulted platform carbonates: an example from the Gozo Island, Malta

2020 ◽  
Author(s):  
Mattia Martinelli ◽  
Andrea Bistaccchi ◽  
Riccardo Castellanza
Keyword(s):  
Damage Zone ◽  
Ore Deposits ◽  
Triaxial Tests ◽  
Normal Faults ◽  
Published Data ◽  
Fault Mechanics ◽  
Zone Width ◽  
Mechanical Stratigraphy ◽  
Study Results ◽  
Platform Carbonates

<p>Fault damage zones (DZ) are fractured volumes of rock that surround the fault core(s), and their structure can have an important role on the control of fault mechanics and of the hydraulic properties of the fault zone, with impact on groundwater flow, ore-deposits, hydrocarbon reservoirs, nuclear waste disposal and contaminant transport in the subsurface. It is generally accepted that DZ width is controlled by fault displacement, and that it increases with increasing offset. However, published data on DZ width in faulted carbonates show a scattering over two orders of magnitude, suggesting that this parameter is controlled also by other factors. Here we present the results of a study performed on two units of the platform carbonates of the Malta and Gozo Islands. These two units, that are cross-cut by normal faults, are characterize by different petrographical, petrophysical and mechanical properties and have completely different Damage Zone width along faults characterized by the same tectonic history and with comparable displacement. More competent and rigid grain-dominated carbonates show DZ thickness of several hundreds of meters, while fracturing in the less competent and more elastic micrite-dominated rocks is developed only very close to the fault core, with a DZ width of few tens of meters. In order to explain this counterintuitive facies-controlled behavior, we performed petrophysical (porosity, density, permeability) and geo-mechanical (Uniaxial, Brazilian, Triaxial tests) analyses to characterize the mechanical stratigraphy and develop a numerical modelling study. Results highlight the heterogeneous stress distribution in a multilayer with variable elastic parameters subjected to horizontal extension. The more elastic unit can more easily expand laterally with respect to the less elastic one with the consequence that σ<sub>3</sub> decrease faster in the last one and this can yield before the more compliant one even if it is stronger. Also the width of the yielding zone is increased in the stiffer layers, leading to a wider DZ.</p>

Modelling of interactions between dykes, inclined sheets and faults at Santorini volcano

2021 ◽  
Author(s):  
Kyriaki Drymoni ◽  
John Browning ◽  
Agust Gudmundsson
Keyword(s):  
Tensile Strength ◽  
Fault Zone ◽  
Numerical Models ◽  
Damage Zone ◽  
Sheet Thickness ◽  
Analytical Models ◽  
Energy Conditions ◽  
Dyke Swarm ◽  
Normal Faults ◽  
Santorini Volcano

<p>Dykes and inclined sheets are known occasionally to exploit faults as parts of their paths, but the conditions that allow this to happen are still not fully understood. Here we report field observations from a well-exposed dyke swarm of the Santorini volcano, Greece, that show dykes and inclined sheets deflected into faults and the results of analytical and numerical models to explain the conditions for deflection. The deflected dykes and sheets belong to a local swarm of 91 dyke/sheet segments that was emplaced in a highly heterogeneous and anisotropic host rock and partially cut by some regional faults and a series of historic caldera collapses, the caldera walls providing, excellent exposures of the structures. The numerical models focus on a normal-fault dipping 65° with a damage zone composed of parallel layers or zones of progressively more compliant rocks with increasing distance from the fault rupture plane. We model sheet-intrusions dipping from 0˚ to 90˚ and with overpressures of alternatively 1 MPa and 5 MPa, approaching the fault. We further tested the effects of changing (1) the sheet thickness, (2) the fault-zone thickness, (3) the fault-zone dip-dimension (height), and (4) the loading by, alternatively, regional extension and compression. We find that the stiffness of the fault core, where a compliant core characterises recently active fault zones, has pronounced effects on the orientation and magnitudes of the local stresses and, thereby, on the likelihood of dyke/sheet deflection into the fault zone. Similarly, the analytical models, focusing on the fault-zone tensile strength and energy conditions for dyke/sheet deflection, indicate that dykes/sheets are most likely to be deflected into and use steeply dipping recently active (zero tensile-strength) normal faults as parts of their paths.</p>

Geometrical characterisation of fault arrays in three dimensions

2021 ◽  
Author(s):  
Vincent Roche ◽  
Giovanni Camanni ◽  
Conrad Childs ◽  
Tom Manzocchi ◽  
John Walsh ◽  
...  
Keyword(s):  
Full Range ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Normal Faults ◽  
Fault Geometry ◽  
Surface Geometry ◽  
Fault Surface ◽  
Mechanical Stratigraphy ◽  
Quantitative Basis ◽  
Geometry Analysis

<p>Normal faults are often complex three-dimensional structures comprising multiple sub-parallel segments separated by intact or breached relay zones. In this study we outline geometrical characterisations capturing this 3D complexity and providing a semi-quantitative basis for the comparison of faults and for defining the factors controlling their geometrical evolution. Relay zones are classified according to whether they step in the strike or dip direction and whether the relay zone-bounding fault segments are unconnected in 3D or bifurcate from a single surface. Complex fault surface geometry is then described in terms of the relative numbers of different types of relay zones to allow comparison of fault geometry between different faults and different geological settings. A large database of 87 fault arrays compiled primarily from mapping 3D seismic reflection surveys and classified according to this scheme, reveals the diversity of 3D fault geometry. Analysis demonstrates that mapped fault geometries depend on geological controls, primarily the heterogeneity of the faulted sequence and the presence of a pre-existing structure. For example, relay zones with an upward bifurcating geometry are prevalent in faults that reactivate deeper structures, whereas the formation of laterally bifurcating relays is promoted by heterogeneous mechanical stratigraphy. In addition, mapped segmentation depends on resolution limits and biases in fault mapping from seismic data. In particular, the results suggest that the proportion of bifurcating relay zones increases as data resolution increases. Overall, where a significant number of relay zones are mapped on a single fault, a wide variety of relay zone geometries occurs, demonstrating that individual faults can comprise segments that are both bifurcating and unconnected in three dimensions. Models for the geometrical evolution of fault arrays must therefore account for the full range of relay zone geometries that appears to be a characteristic of all faults.</p>

scholarly journals Influence of basement rocks on fluid evolution during multiphase deformation: the example of the Estamariu thrust in the Pyrenean Axial Zone

2020 ◽  
Author(s):  
Daniel Muñoz-López ◽  
Gemma Alías ◽  
David Cruset ◽  
Irene Cantarero ◽  
Cédric M. Jonh ◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Normal Faults ◽  
Published Data ◽  
Fluid Migration ◽  
Rock Interaction ◽  
Fluid Chemistry ◽  
Vein Formation ◽  
Basement Rocks ◽  
Calcite Veins

Abstract. Calcite veins precipitated in the Estamariu thrust during two tectonic events decipher the temporal and spatial relationships between deformation and fluid migration in a long-lived thrust and determine the influence of basement rocks on the fluid chemistry during deformation. Structural and petrological observations constrain the timing of fluid migration and vein formation, whilst geochemical analyses (δ13C, δ18O, 87Sr/86Sr, clumped isotope thermometry and elemental composition) of the related calcite cements and host rocks indicate the fluid origin, pathways and extent of fluid-rock interaction. The first tectonic event, recorded by calcite cements Cc1a and Cc2, is related to the Alpine reactivation of the Estamariu thrust, and is characterized by the migration of meteoric fluids, heated at depth (temperatures between 56 and 98 °C) and interacted with crystalline basement rocks before upflowing through the thrust zone. During the Neogene extension, the Estamariu thrust was reactivated and normal faults and shear fractures with calcite cements Cc3, Cc4 and Cc5 developed. Cc3 and Cc4 precipitated from hydrothermal fluids (temperatures between 127 and 208 °C and between 102 and 167 °C, respectively) derived from crystalline basement rocks and expelled through fault zones during deformation. Cc5 precipitated from low temperature meteoric waters percolating from the surface through small shear fractures. The comparison between our results and already published data in other structures from the Pyrenees suggests that regardless of the origin of the fluids and the tectonic context, basement rocks have a significant influence on the fluid chemistry, particularly on the 87Sr/86Sr ratio. Accordingly, the cements precipitated from fluids interacted with crystalline basement rocks have significantly higher 87Sr/86Sr ratios (> 0.710) with respect to those precipitated from fluids that have interacted with the sedimentary cover (

Simultaneous compared to interval administration of mifepristone and misoprostol for medical abortion up to 10+0 weeks' gestation: a systematic review with meta-analyses

2020 ◽  
pp. bmjsrh-2019-200448
Author(s):  
Mia Schmidt-Hansen ◽  
Jonathan Lord ◽  
Elise Hasler ◽  
Sharon Cameron
Keyword(s):  
Systematic Review ◽  
Meta Analysis ◽  
Cochrane Collaboration ◽  
Medical Abortion ◽  
Cochrane Library ◽  
Published Data ◽  
Study Results ◽  
Randomised Controlled ◽  
Meta Analyses

BackgroundMedical abortion with mifepristone and misoprostol usually involves an interval of 36–48 hours between administering these drugs; however, it is possible that the clinical efficacy at early gestations may be maintained when the drugs are taken simultaneously. The objective of this systematic review was to determine the safety and effectiveness of simultaneous compared with interval administration of mifepristone and misoprostol for abortion up to 10+0 weeks’ gestation.MethodsWe searched Embase Classic, Embase; Ovid MEDLINE(R) including Daily, and Epub Ahead-of-Print, In-Process & Other Non-Indexed Citations; and Cochrane Library on 11 December 2019. We included randomised controlled trials (RCTs), published in English from 1985, comparing simultaneous to interval administration of mifepristone and misoprostol for early abortion. Risk of bias was assessed using the Cochrane Collaboration checklist for RCTs. Meta-analysis of risk ratios (RRs) using the Mantel-Haenszel method were performed. The quality of the evidence was assessed using GRADE.ResultsMeta-analyses of three RCTs (n=1280) showed no differences in ‘ongoing pregnancy’ (RR 1.78, 95% CI 0.38 to 8.36), ‘haemorrhage requiring transfusion or ≥500 mL blood loss’ (RR 0.11, 95% CI 0.01 to 2.03) and ‘incomplete abortion with the need for surgical intervention’ (RR 1.30, 95% CI 0.76 to 2.25) between the interventions. Individual study results showed no difference in patient satisfaction, or ‘need for repeat misoprostol’, although ‘time to onset of bleeding or cramping’ was longer after simultaneous than interval administration. The quality of evidence was very low to moderate.ConclusionThe published data support the use of simultaneous mifepristone and misoprostol for medical abortion up to 9+0 weeks in women who prefer this method of administration.

scholarly journals Geophysical Prospecting Using ERT and IP Techniques to Locate Galena Veins

2019 ◽  
Vol 11 (24) ◽  
pp. 2923 ◽  
Author(s):  
Julián Martínez ◽  
Javier Rey ◽  
Senén Sandoval ◽  
Mª Camen Hidalgo ◽  
Rosendo Mendoza
Keyword(s):  
Sedimentary Cover ◽  
Ore Deposits ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Normal Faults ◽  
Mining District ◽  
Geophysical Prospecting ◽  
Geophysical Research ◽  
Electrical Sounding

The aim of this study is to prove the effectiveness of two electrical geophysical prospecting techniques, namely electrical resistivity tomography (ERT) and induced polarization (IP), in locating thin vein structures of metal sulphides embedded in Palaeozoic materials underlying a sedimentary cover. For this purpose, a Quaternary basin known as La Garza was selected, located in the mining district of Linares-La Carolina (Southern Spain). Galena (PbS) veins appear abundantly throughout this area, hosted in the Palaeozoic granitic bedrock. The studied veins show thicknesses from 0.5 to 2.0 m, and most present a vertical planar distribution. The veins lose their continuity below the sedimentary cover due to normal fractures that control the subsidence of the basin. During the 1980s, geophysical research campaigns were carried out in La Garza using vertical electrical sounding and failed in detecting the hidden veins. For this reason, to carry out this study, a closed regular mesh was designed, composed by eight ERT and IP profiles, with variable lengths between 315 and 411 metres. An electrode spacing between 5 and 7 metres was selected, thus allowing the granite bedrock to be reached without significantly reducing the resolution capabilities of the method. Even though ERT and IP are well-known geophysical techniques for mapping ore deposits, this is a case study that shows the advantages of the simultaneous use of both techniques (ERT and IP), over their individual application. ERT allows for reconstructing the morphology of the basin and the fractures that control it due to high-resistivity contrast between the overlying sedimentary cover and the underlaying granitic basement. However, it cannot provide any insights about their degree of mineralization. At this point, it is the IP technique that makes it possible to differentiate which are the mineralized structures. Some of these fractures produce high (above 50 mV/V) and moderate (below 50 mV/V) chargeability values, suggesting the existence of several unexploited metal veins. Furthermore, the derived models enable researchers to analyse the morphology of this sedimentary basin controlled by normal faults.

Factors controlling fracture distribution within a carbonate-hosted relay ramp: insights from the Tre Monti fault (Central Apennines)

2020 ◽  
Author(s):  
Marco Mercuri ◽  
Eugenio Carminati ◽  
Maria Chiara Tartarello ◽  
Marco Brandano ◽  
Paolo Mazzanti ◽  
...  
Keyword(s):  
Shallow Water ◽  
Damage Zone ◽  
Central Italy ◽  
Hydrocarbon Exploration ◽  
Fault Mechanics ◽  
Fracture Density ◽  
Carbonate Facies ◽  
High Fracture ◽  
Main Fault ◽  
Fracture Distribution

<p>Fractures constitute the main pathway for fluids in fault damage zones hosted in low-porosity rocks. Understanding the factors controlling fracture distribution is hence fundamental to better assess fluids circulation in fault damage zones, with evident implications for fault mechanics, hydrogeology and hydrocarbon exploration. Being usually characterized by a strong damage and structural complexity, this is of particularly importance for relay zones.</p><p>We integrated classical and modern structural geology techniques to investigate the factors controlling fracture distribution within a portion of a relay ramp damage zone pertaining to the Tre Monti fault (Central Italy). The damage zone is hosted within peritidal carbonates and located at the footwall of the relay ramp front segment. We analysed the distribution of the fracture density in the outcrop through (1) scanlines measured in the field, (2) oriented rock samples, and (3) scan-areas performed on a virtual outcrop model obtained by aerial structure-from-motion.</p><p>Our results highlight structural and lithological control on fracture distribution. Scanlines and virtual scan-areas show that fracture density increases with the distance from the front segment of the relay ramp. Moreover, all the methods highlight that supratidal and intertidal carbonate facies exhibit higher fracture density than subtidal limestones.</p><p>This apparently anomalous trend of fracture density, that increases moving away from a main fault segment, has two main explanations. (1) The damage is associated with the relay ramp development: approaching the centre of the relay ramp (i.e., moving away from the front segment) an increase in the number of subsidiary faults with their associated damage zones promotes high fracture densities. (2) The increase in fracture density can be attributed to the increasing content in supratidal and intertidal carbonate facies that are more abundant in the centre of the relay ramp.</p><p>Our results provide important suggestions for factors controlling fracture distribution and fluid flow within relay ramps hosted by shallow water limestones. We show that the trend of fracture distribution with respect to a main fault is not easily predictable in presence of a relay ramp, because it can be modulated by the subsidiary faults formation and slip during the relay ramp development. Moreover, carbonate facies play a non-negligible role in fracture distribution within fault zones hosted in shallow-water carbonates.</p>

Controls on fault damage zone width, structure, and symmetry in the Bandelier Tuff, New Mexico

2010 ◽  
Vol 32 (6) ◽  
pp. 766-780 ◽  
Author(s):  
Paul R. Riley ◽  
Laurel B. Goodwin ◽  
Claudia J. Lewis
Keyword(s):  
New Mexico ◽  
Damage Zone ◽  
Zone Width ◽  
Bandelier Tuff ◽  
Fault Damage Zone

scholarly journals Humoral and cellular immunity and the safety of COVID-19 vaccines: a summary of data published by 21 May 2021

2021 ◽  
Vol 33 (10) ◽  
pp. 529-540
Author(s):  
Kun Xu ◽  
Lianpan Dai ◽  
George F Gao
Keyword(s):  
Immune Responses ◽  
Viral Genome ◽  
Vaccine Development ◽  
Published Data ◽  
Humoral And Cellular Immunity ◽  
Cellular Immune Responses ◽  
Rapid Responses ◽  
Study Results ◽  
Protection Efficacy ◽  
Cellular Immune

Abstract Coronavirus disease 2019 (COVID-19) has caused millions of deaths, and serious consequences to public health, economies and societies. Rapid responses in vaccine development have taken place since the isolation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the release of the viral genome sequence. By 21 May 2021, 101 vaccines were under clinical trials, and published data were available for 18 of them. Clinical study results from some vaccines indicated good immunogenicity and acceptable reactogenicity. Here, we focus on these 18 vaccines that had published clinical data to dissect the induced humoral and cellular immune responses as well as their safety profiles and protection efficacy.

Patience Cowie and the Inception of Modern Fault Mechanics:  A Recollection

2021 ◽  
Author(s):  
Christopher H. Scholz
Keyword(s):  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Slip Length ◽  
Scaling Law ◽  
Damage Zone ◽  
Zone Model ◽  
Fault Mechanics ◽  
Length Relationship ◽  
Length Scaling ◽  
Struct Geol

<p>Patience Cowie’s PhD thesis, conducted with me at Lamont, resulted in three papers, published in 1992, that laid the groundwork for the modern era of fault mechanics studies. In the first paper<sup>1</sup> she reasoned that a cohesive zone model provided a plausible model of fault grown provided that the width of the cohesive zone scales linearly with fault length. In that case, the Griffith instability is avoided and faults grow self-similarly in quasistatic equilibrium. This model is consistent with the existence of faults of all sizes in which displacement scales linearly with length and the fault grows by the breakdown of a damage zone at the fault tip. In the second paper<sup>2</sup> she showed that the then existing data for fault displacement and length were consistent with linear scaling for faults rupturing rock of similar strength. In the third paper<sup>3</sup> she combined the earthquake slip/length scaling law with that fault scaling law to show how faults can grow by the accumulation of slip from earthquakes.</p><p>In the subsequent thirty years much more work has been done to expand on these themes pioneered by Patience. Here I share some memories of working with Patience in those formative years.</p><p> </p><p>1          Cowie, P. A. & Scholz, C. H. Physical explanation for the displacement-length relationship of faults using a post-yield fracture mechanics model. J.       Struct. Geol. <strong>14</strong>, 1133-1148 (1992).</p><p>2          Cowie, P. A. & Scholz, C. H. Displacement-length scaling relationship for faults: data synthesis and discussion. J. Struct. Geol. <strong>14</strong>, 1149-1156 (1992).</p><p>3          Cowie, P. A., and Scholz, C.H. Growth of faults by accumulation of seismic slip. J. Geophys. Res. <strong>97(B7)</strong>, 11085-11095 (1992b).</p>

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