121 research outputs found

    How do plate boundary fault cores evolve and why? : a case study of the highland boundary fault, Scotland

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    Understanding the internal structure (i.e., fault core composition, thickness and geometry) of large faults is crucial because their fault structure and properties control how and where earthquakes occur. Compilations of data from multiple fault studies show that fault cores get thicker on average with increasing total displacement (and hence slip events). However, the majority of faults in these datasets are from intraplate settings (faults within the interior of tectonic plates). Plate boundary faults have largely been excluded. As such there are no studies that systematically compare the two fault systems. This study aims to address this knowledge gap: compiling and harmonising a global dataset of intraplate and plate boundary fault core thickness and total displacement data in order to examine whether these fault systems evolve in a similar way with repeated slip events. The Highland Boundary fault (HBF), an ancient plate boundary fault in Scotland, is used as a field site to provide a case study for examining the internal structure and inferring the evolution of a plate boundary fault core. Detailed field, laboratory and mineralogical work reveal that the HBF core consists of four distinct units that remain unmixed. Not every unit is continuous along-strike and each unit varies in thickness (between 2.95 and 10.7 m). The units remain distinct as they formed at different stages of faulting and by different mechanisms affecting the faults ability to host earthquakes through time. For the first time, this work discovers quantitatively that plate boundary fault cores are narrower than predicted by the trend for intraplate faults and highlights that, for this reason, plate boundary faults do not dissipate as much energy as intraplate faults during earthquakes. These results are crucial for understanding the internal structure and evolution of plate boundary fault cores and have implications for understanding how earthquakes behave.Understanding the internal structure (i.e., fault core composition, thickness and geometry) of large faults is crucial because their fault structure and properties control how and where earthquakes occur. Compilations of data from multiple fault studies show that fault cores get thicker on average with increasing total displacement (and hence slip events). However, the majority of faults in these datasets are from intraplate settings (faults within the interior of tectonic plates). Plate boundary faults have largely been excluded. As such there are no studies that systematically compare the two fault systems. This study aims to address this knowledge gap: compiling and harmonising a global dataset of intraplate and plate boundary fault core thickness and total displacement data in order to examine whether these fault systems evolve in a similar way with repeated slip events. The Highland Boundary fault (HBF), an ancient plate boundary fault in Scotland, is used as a field site to provide a case study for examining the internal structure and inferring the evolution of a plate boundary fault core. Detailed field, laboratory and mineralogical work reveal that the HBF core consists of four distinct units that remain unmixed. Not every unit is continuous along-strike and each unit varies in thickness (between 2.95 and 10.7 m). The units remain distinct as they formed at different stages of faulting and by different mechanisms affecting the faults ability to host earthquakes through time. For the first time, this work discovers quantitatively that plate boundary fault cores are narrower than predicted by the trend for intraplate faults and highlights that, for this reason, plate boundary faults do not dissipate as much energy as intraplate faults during earthquakes. These results are crucial for understanding the internal structure and evolution of plate boundary fault cores and have implications for understanding how earthquakes behave

    The growth of faults and fracture networks in a mechanically evolving, mechanically stratified rock mass : a case study from Spireslack Surface Coal Mine, Scotland

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    Fault architecture and fracture network evolution (and resulting bulk hydraulic properties) are highly dependent on the mechanical properties of the rocks at the time the structures developed. This paper investigates the role of mechanical layering and pre-existing structures on the evolution of strike–slip faults and fracture networks. Detailed mapping of exceptionally well exposed fluvial–deltaic lithologies at Spireslack Surface Coal Mine, Scotland, reveals two phases of faulting with an initial sinistral and later dextral sense of shear with ongoing pre-faulting, syn-faulting, and post-faulting joint sets. We find fault zone internal structure depends on whether the fault is self-juxtaposing or cuts multiple lithologies, the presence of shale layers that promote bed-rotation and fault-core lens formation, and the orientation of joints and coal cleats at the time of faulting. During ongoing deformation, cementation of fractures is concentrated where the fracture network is most connected. This leads to the counter-intuitive result that the highest-fracture-density part of the network often has the lowest open fracture connectivity. To evaluate the final bulk hydraulic properties of a deformed rock mass, it is crucial to appreciate the relative timing of deformation events, concurrent or subsequent cementation, and the interlinked effects on overall network connectivity

    Community-level sensitivity of a calcifying ecosystem to acute in situ CO2 enrichment

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    The rate of change in ocean carbonate chemistry is a vital determinant in the magnitude of effects observed. Benthic marine ecosystems are facing an increasing risk of acute CO2 exposure that may be natural or anthropogenically derived (e.g. engineering and industrial activities). However, our understanding of how acute CO2 events impact marine life is restricted to individual organisms, with little understanding for how this manifests at the community level. Here, we investigated in situ the effect of acute CO2 enrichment on the coralline algal ecosystem—a globally ubiquitous, ecologically and economically important habitat, but one which is likely to be sensitive to CO2 enrichment due to its highly calcified reef-like structures engineered by coralline algae. Most notably, we observed a rapid community-level shift to favour net dissolution rather than net calcification. Smaller changes from net respiration to net photosynthesis were also observed. There was no effect on the net flux of DMS/DMSP (algal secondary metabolites), nor on the nutrients nitrate and phosphate. Following return to ambient CO2 levels, only a partial recovery was seen within the monitoring timeframe. This study highlights the sensitivity of biogenic carbonate marine communities to acute CO2 enrichment and raises concerns over the capacity for the system to ‘bounce back’ if subjected to repeated acute high-CO2 events

    Core surprise : Characterising the internal structure of an ancient plate boundary fault in Scotland

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    Knowledge of the structure and rheology of large, earthquake-hosting plate boundary faults is lacking as they are normally poorly exposed or difficult to find on the surface. Recently, several drilling projects have been undertaken to explore the internal structure of active plate boundary fault zones at depth to understand how this constrains seismic slip behaviour. All of these projects highlight the presence and importance of clay-rich rocks within the fault core in controlling slip behaviour along these large faults. The Highland Boundary fault (HBF) in Scotland, provides a rare opportunity to study the internal fault architecture of a well-exposed along-strike section of an ancient plate boundary fault. The HBF extends for over 240 km, however, is only well-exposed along a 560 m section at Stonehaven. Here, serpentinite juxtaposes quartzofeldspathic crustal rocks, a common feature at many plate boundaries (e.g., sections of the San Andreas fault and Alpine fault, New Zealand). We collected six across-fault transects aiming to capture the internal structure of the HBF and its along-strike variability. Within the fault core we discover four mechanically and chemically distinct clay-rich units, which have sharp contacts. Despite evidence of internal strain within the clay-rich fault rocks, relatively intact clasts of wall rock and microfossils are preserved. From mineralogical observations it can be interpreted that the clay-rich rocks along this section of the HBF, formed through fluid-assisted, shear-enhanced chemical reactions between wall rocks of contrasting chemistry. Our field evidence also demonstrates that plate boundary faults can be structurally variable along strike at various scales. The total thickness of the fault core varies from 3 to 10.7 m over an along strike distance of 560 m. Not every unit is laterally continuous along strike, and each unit varies in thickness. We compare our observations with studies on other plate boundary systems. For example, the HBF has analogous thickness and mineralogy to drill core recovered from the San Andreas fault. Highly variable fault core structures and related properties such as mineralogy, may exert significant control on earthquake rupture and slip behaviour at large plate boundaries

    Identifying, managing and supporting patients with a rare disease

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    Rare diseases (RDs) are defined as diseases that affect less than 1 in 2000 people, 71.9% are genetic and 69.9% have symptom onset in childhood. There are an estimated 8000 rare diseases, and although individually rare, collectively they are common, with a prevalence of 3.5–5.9%, similar to diseases such as asthma and diabetes. Although rare diseases may be considered the domain of specialists, the identification, management and support of ‘rare disease’ patients and their families falls within the competence of GPs

    Core surprise : what's inside a plate boundary?

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    Despite the fact that 90% of global seismicity occurs at plate boundary faults, our understanding of their internal structure is lacking. It’s not easy to see inside a plate boundary fault – typically composed of a high-strain fault core surrounded by a fractured damage zone – and when we can, it often requires expensive drilling projects that yield limited information on the internal structure of the whole fault. Understanding the internal structure of large faults is crucial, because their chemical and mechanical properties control how and where earthquakes rupture, nucleate and propagate. This in turn limits the size of the earthquake or the amount of radiated seismic energy, and consequently the severity of surface damage. The 1999 magnitude 7.7 earthquake along the Chelungpu plate boundary fault, for example – the second deadliest earthquake in Taiwan’s recorded history – saw significant variations in slip and ground motion at different locations along the fault which resulted in large local variations in casualties and damage. Subsequent field investigations related these variations to changes in the fault’s structure (i.e., clay width, geometry), which in turn controlled how the fault moved

    Research Report for COVID-19 Public Inquiry

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    This report was commissioned by the Scottish Covid-19 Inquiryas introductory scoping research

    Measuring the Impact of the COVID-19 Pandemic on Diagnostic Delay in Rare Disease

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    Rare diseases are individually rare but collectively common, with a combined prevalence of 3.5–5.9%. A common feature of many diseases is a substantial delay in patients receiving a correct diagnosis; this protracted path to diagnosis is termed ‘the diagnostic odyssey’. During the COVID-19 pandemic, significant concerns have emerged from both clinicians and patients regarding a disproportionate effect of the pandemic on diagnosis and management of rare disease. Such concerns prompted a study to explore this question further, the results of which are presented here. A cross-sector multi-stakeholder coalition was formed, Action for Rare Disease Empowerment (ARDEnt), with representation from patients with rare diseases and carers, patient advocacy groups, clinicians, academics, data scientists, and industry. A mixed methods approach was used to collect and collate information about the impact of the pandemic on diagnostic delay in rare disease. Currently, there is a lack of systematic recording and reporting of rare disease diagnosis in the UK, which created challenges in directly measuring diagnosis rates. Therefore, the group was dependent on a mix of data sources to reflect healthcare provided during 2020 compared with previous years. The findings were synthesised to describe the impact of the pandemic along the path to diagnosis, from the moment of first concern and engagement with health services, to the availability of definitive testing. In conclusion, evidence suggests the pandemic has exacerbated the problem of diagnostic delay for rare diseases, affecting all points on the path to diagnosis. The authors recommend three actions to help address this: optimising remote clinical consultations; enhancing the use of health informatics in rare diseases; and proactively identifying patients with undiagnosed rare diseases missed due to the pandemic. This study also highlights the need for better reporting of rare disease diagnoses, a core metric to measure the impact of health system changes that may be put into place to address the priorities of The UK Rare Diseases Framework, also published this year

    The 1990 update to strategy for exploration of the inner planets

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    The Committee on Planetary and Lunar Exploration (COMPLEX) has undertaken to review and revise the 1978 report Strategy for Exploration of the Inner Planets, 1977-1987. The committee has found the 1978 report to be generally still pertinent. COMPLEX therefore issues its new report in the form of an update. The committee reaffirms the basic objectives for exploration of the planets: to determine the present state of the planets and their satellites, to understand the processes active now and at the origin of the solar system, and to understand planetary evolution, including appearance of life and its relation to the chemical history of the solar system
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