24 research outputs found
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Seismological and Geophysical Signatures of the Deep Crustal Magma Systems of the Cenozoic Volcanic Fields Beneath the Eifel, Germany
The Quaternary volcanic fields of the Eifel (Rhineland-Palatinate, Germany) had their last eruptions less than 13,000 years ago. Recently, deep low-frequency (DLF) earthquakes were detected beneath one of the volcanic fields showing evidence of ongoing magmatic activity in the lower crust and upper mantle. In this work, seismic wide- and steep-angle experiments from 1978/1979 and 1987/1988 are compiled, partially reprocessed and interpreted, together with other data to better determine the location, size, shape, and state of magmatic reservoirs in the Eifel region near the crust-mantle boundary. We discuss seismic evidence for a low-velocity gradient layer from 30–36 km depth, which has developed over a large region under all Quaternary volcanic fields of the Rhenish Massif and can be explained by the presence of partial melts. We show that the DLF earthquakes connect the postulated upper mantle reservoir with the upper crust at a depth of about 8 km, directly below one of the youngest phonolitic volcanic centers in the Eifel, where CO2 originating from the mantle is massively outgassing. A bright spot in the West Eifel between 6 and 10 km depth represents a Tertiary magma reservoir and is seen as a model for a differentiated reservoir beneath the young phonolitic center today. We find that the distribution of volcanic fields is controlled by the Variscan lithospheric structures and terrane boundaries as a whole, which is reflected by an offset of the Moho depth, a wedge-shaped transparent zone in the lower crust and the system of thrusts over about 120 km length. ©2020. The Authors
Health and social care: The link between social care deficiencies and health care pressures
In the United Kingdom, demand on the social care sector is rising coupled with a significant reduction in funding making it difficult to meet these needs. The aim of this two-part commentary is to provide a critical evaluation of the evidence base in relation to solutions to tackle the growing demands on health and social care. Part 1 focuses on the evidence from a systematic review around the association between the availability and supply of social care and healthcare on utilisation for older adults in high income countries
Health and social care: Is integration of care to meet growing demands effective?
Integration of care has been suggested as a solution to overcome the increasing financial and service pressures on the healthcare system. The aim of this second part of a two-part commentary is to critically evaluate a systematic review that investigated the national and international evidence base in relation to outcomes of integrated care on actual and perceived service delivery, and to identify implication for practice, policy and future research based on the quality of evidence
RomUkrSeis : seismic model of the crust and upper mantle across the Eastern Carpathians – from the Apuseni Mountains to the Ukrainian Shield
RomUkrSeis was carried out by a consortium of organisations, the Faculty of Geology and Geophysics and the Doctoral School of Geology of the University of Bucharest (Romania), the Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine (Kiev), the Institute of Geophysics of the Polish Academy of Sciences (Warsaw), the Deutsches GeoForschungsZentrum (Potsdam) and the School of Geosciences of the University of Aberdeen (Scotland). Financial support for drilling/shooting works on the territory of Romania came from S.C. Prospectiuni S.A. (with a special mention to former CEO Gehrig Stannard Schultz, currently at EPI Group, United Kingdom), Hunt Oil of Romania, Repsol Romania and on the territory of Ukraine from Ukrgeofizika. Participation of the Polish group in this work was supported within statutory activities No 3841/E-41/S/2014-2020 of the Ministry of Science and Higher Education of Poland. The authors express their sincere appreciation of the activities of many people who took part in field work and data acquisition. A large part of the instrumentation was provided by the Geophysical Instrument Pool of the Deutsches GeoForschungsZentrum (GFZ), Potsdam, Germany. Christian Haberland is thanked for his support and kindness facilitating the loan of this equipment to the RomUkrSeis consortium. The public domain packages GMT (Wessel and Smith, 1995) and Seismic Unix (Cohen and Stockwell Jr., 1997) were used in the preparation of maps and for seismic data processing. Tesseral Technologies Inc. (Calgary) developed the software for the full waveform modelling and we express our gratitude to their staff for technical support. The authors also wish to thank Professor Richard England (University of Leicester) and an anonymous reviewer for their constructive comments on an earlier version of this manuscript. This version is much improved as a result.Peer reviewedPostprin
The Impact of GeneXpert Cerebrospinal Fluid Testing on Tuberculous Meningitis Diagnosis in Routine Care in Botswana.
BACKGROUND: Tuberculous meningitis (TBM) disproportionately impacts high-HIV prevalence, resource-limited settings where diagnosis is challenging. The GeneXpert platform has utility in TBM diagnosis, but uptake remains limited. In Botswana, before the introduction of GeneXpert, tuberculosis (TB) testing was only available through mycobacterial culture at the National TB Reference Laboratory. Data describing routine use of Xpert MTB/RIF for cerebrospinal fluid (CSF) testing in resource-limited settings are scarce. METHODS: Electronic records for patients with CSF tested in government facilities in Botswana between 2016 and 2022 were obtained from a central online repository as part of ongoing national meningitis surveillance. Samples were excluded from 1 site where Xpert MTB/RIF is performed universally. The proportion receiving TB-specific investigation on CSF and the number positive for Mycobacterium tuberculosis following increased Xpert MTB/RIF capacity were determined. RESULTS: The proportion of CSF samples receiving TB-specific investigation increased from 4.5% (58/1288) in 2016 to 29.0% (201/693) in 2022, primarily due to increased analysis with Xpert MTB/RIF from 0.9% (11/1288) to 23.2% (161/693). There was an overall decline in the annual number of CSF samples analyzed, but the proportion with microbiologically confirmed TBM increased from 0.4% to 1.2%. The proportion of samples tested for TB that were collected from health care facilities >100 km from the National TB Reference Laboratory increased with Xpert MTB/RIF rollout from 65.9% (87/132) to 78.0% (494/633). CONCLUSIONS: In Botswana, access to TB culture is challenging in remote populations; more accessible near-patient testing using Xpert MTB/RIF increased the number of patients receiving TB-specific testing on CSF and the number of confirmed TBM cases
Tracking cryptococcal meningitis to monitor HIV program success during the Treat-All era: an analysis of national data in Botswana.
BACKGROUND: Cryptococcal meningitis causes substantial mortality in high-HIV prevalence African countries despite advances in disease management and increasing antiretroviral therapy coverage. Reliable diagnosis of cryptococcal meningitis is cheap and more accessible than other indicators of AHD burden such as CD4 testing or investigation for disseminated tuberculosis; therefore, monitoring cryptococcal meningitis incidence has the potential to serve as a valuable metric of HIV programmatic success. METHODS: Botswana national meningitis surveillance data from 2015 to 2022 were obtained from electronic health records. All electronic laboratory records from cerebrospinal fluid samples analysed within government healthcare facilities in Botswana were extracted from a central online repository. Adjustments for missing data were made through triangulation with prospective cohort study datasets. Cryptococcal meningitis case frequency was enumerated using a case definition and incidence calculated using national census data. RESULTS: A total of 1,744 episodes of cryptococcal meningitis were identified; incidence declined from 15.0 (95% CI 13.4-16.7) cases/100,000 person-years in 2015 to 7.4 (95% CI 6.4-8.6) cases/100,000 person-years in 2022. However, the rate of decline slowed following the introduction of universal treatment in 2016. The highest incidence was observed in men and individuals aged 40-44. The proportion of cases diagnosed through cryptococcal antigen testing increased from 35.5% to 86.3%. CONCLUSION: Cryptococcal meningitis incidence has decreased in Botswana following expansion of ART coverage but persists at a stubbornly high incidence. Most cases are now diagnosed through the cheap and easy-to-use cryptococcal antigen test highlighting the potential of using cryptococcal meningitis as key metric of programme success in the Treat All era
Upper mantle temperature and the onset of extension and break-up in Afar, Africa
It is debated to what extent mantle plumes play a role in continental rifting and eventual break-up. Afar lies at the northern end of the largest and most active present-day continental rift, where the East African Rift forms a triple junction with the Red Sea and Gulf of Aden rifts. It has a history of plume activity yet recent studies have reached conflicting conclusions on whether a plume still contributes to current Afar tectonics. A geochemical study concluded that Afar is a mature hot rift with 80 km thick lithosphere, while seismic data have been interpreted to reflect the structure of a young, oceanic rift basin above mantle of normal temperature. We develop a self-consistent forward model of mantle flow that incorporates melt generation and retention to test whether predictions of melt chemistry, melt volume and lithosphere–asthenosphere seismic structure can be reconciled with observations. The rare- earth element composition of mafic samples at the Erta Ale, Dabbahu and Asal magmatic segments can be used as both a thermometer and chronometer of the rifting process. Low seismic velocities require a lithosphere thinned to 50 km or less. A strong positive impedance contrast at 50 to 70 km below the rift seems linked to the melt zone, but is not reproduced by isotropic seismic velocity alone. Combined, the simplest interpretation is that mantle temperature below Afar is still elevated at 1450◦C, rifting started around 22–23 Ma, and the lithosphere has thinned from 100 to 50 km to allow significant decompressional melting
Evidence that non-linear elasticity contributes to the seismic coda
SUMMARY Different factors might affect the propagation of seismic waves producing scattering, including heterogeneities and non-linear elasticity. A key difference between these two factors is the dependence of the strength of the scattered waves on the strength of the incident wave, being linear for the former and non-linear for the latter. A detailed study of the TIPTEQ data, where about a hundred explosions were recorded on 180 three-component stations in the distance range of approximately 0-100 km, shows that this dependence is non-linear. Data were analyzed in the following way: (i) the envelope of bandpass filtered data between 10 and 40 Hz was obtained for a large number of stations from different distance ranges and charge sizes of shots, (ii) for these distances we modeled the envelope considering the non-linear elasticity. The shapes of the theoretical and observed envelopes were in general very similar. A scale factor for each case was obtained considering the best fit of its complete envelope, and (iii) since this scale factor depends mainly on the size of the explosion, we computed the ratio (R) of the scale factor (sf ) for different sizes of explosions at the same distance. Finally, varying the distance between 0 and 50 km, (iv) we computed the power (p) of the dependence of the ratio (R) on the ratio of the charge sizes (R = ( For the complete data set we obtain a value of p = 2.5 ± 0.9, which is clearly greater than 1. This shows that non-linear 2 Calisto et al. elasticity is an important factor in the contribution to seismic wave scattering in the frequency range of 10-40 Hz
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Upper Crustal Weak Zone in Central Tibet: An Implication From Three‐Dimensional Seismic Velocity and Attenuation Tomography Results
A series of conjugate strike‐slip faults is the most prominent geologic feature in central Tibet and is considered to accommodate east‐west extension and coeval north‐south contraction. The development mechanism of the conjugate strike‐slip fault system is under debate because of unclear crustal physical properties and compositional variations. P and S wave arrivals from 414 local earthquakes recorded by the temporary Seismic Array Integrated Detection for a Window of Indian Continental Head array and the permanent China National Seismic Network were used for the velocity tomography, with additional P and S wave arrivals from 12 shots of the International Deep Profiling of Tibet and the Himalaya III reflection/refraction profile. The local earthquakes were simultaneously relocated with the updated velocity models. We also inverted for a three‐dimensional upper crustal Qp model with the same earthquake data set. The Vp structure near the surface shows that low‐Vp anomalies generally correspond to sedimentary basins and high‐Vp anomalies are related to exhumed metamorphic blocks in the study area. Relatively low Vp/Vs ratios in the upper crust indicate widely distributed quartz‐rich rocks. The low‐Vp zone from 0‐ to 10‐km depth (resolving depth limit) is spatially correlated with the Bangong‐Nujiang suture, possibly reflecting the compositional difference along the ophiolitic mélange belt accompanied by twin volcanic arcs from a double‐sided subduction. This interpretation is supported by relatively heterogeneous Qp values. This low‐velocity zone also implies relatively uniform stress and continuous deformation in the upper crust of central Tibet. The relatively weak materials in at least the upper crust would result in strain concentration and help the development of the conjugate strike‐slip fault system along the Bangong‐Nujiang suture.
Key Points
Seismic data from 53 temporary and 10 permanent stations are used to conduct velocity and attenuation tomography for central Tibet
Shallow low‐ and high‐Vp anomalies generally correspond to sedimentary basins and exhumed metamorphic blocks in the study area
Upper crustal (or deeper) low‐Vp zone along the Bangong‐Nujiang suture reflects compositional difference along the ophiolitic mélange bel
Seismological and Geophysical Signatures of the Deep Crustal Magma Systems of the Cenozoic Volcanic Fields Beneath the Eifel, Germany
The Quaternary volcanic fields of the Eifel (Rhineland-Palatinate, Germany) had their last eruptions less than 13,000 years ago. Recently, deep low-frequency (DLF) earthquakes were detected beneath one of the volcanic fields showing evidence of ongoing magmatic activity in the lower crust and upper mantle. In this work, seismic wide- and steep-angle experiments from 1978/1979 and 1987/1988 are compiled, partially reprocessed and interpreted, together with other data to better determine the location, size, shape, and state of magmatic reservoirs in the Eifel region near the crust-mantle boundary. We discuss seismic evidence for a low-velocity gradient layer from 30–36 km depth, which has developed over a large region under all Quaternary volcanic fields of the Rhenish Massif and can be explained by the presence of partial melts. We show that the DLF earthquakes connect the postulated upper mantle reservoir with the upper crust at a depth of about 8 km, directly below one of the youngest phonolitic volcanic centers in the Eifel, where CO2 originating from the mantle is massively outgassing. A bright spot in the West Eifel between 6 and 10 km depth represents a Tertiary magma reservoir and is seen as a model for a differentiated reservoir beneath the young phonolitic center today. We find that the distribution of volcanic fields is controlled by the Variscan lithospheric structures and terrane boundaries as a whole, which is reflected by an offset of the Moho depth, a wedge-shaped transparent zone in the lower crust and the system of thrusts over about 120 km length