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The lithosphere of South America from seismic tomography: Structure, evolution, and control on tectonics and magmatism
Full text linkThe thickness, temperature and mechanical strength of the lithosphere vary greatly across South America and have controlled tectonic and magmatic processes during its evolution. Here, we introduce a new tomographic model of South America’s lithosphere and underlying mantle, SACI-24, and analyse this and other state-of-the-art models together with other geological and geophysical data. The new model is obtained by waveform inversion of surface, S and multiple S waveforms globally, but is optimised for South America and the surrounding oceans. SACI-24 is constrained by ∼ 970,000 seismograms from 9259 stations and maps detailed structure of cratonic lithosphere across the continent, highlighting previously unknown complexities and fragmentation. Within the Amazon Craton, the Guiana and Central Brazil blocks show high Vs exceeding 4.8 km/s in the 80–150 km depth range but are separated by lower velocities below the Amazon Basin, matching the locations of ancient rifting and the flood basalts of the Central Atlantic Magmatic Province. In the São Francisco Craton, high velocities extend north and southwest beyond the previously proposed boundaries. Warmer, thinner lithosphere underlies the Paramirim and Pirapora aulacogens, locations of magmatic and rifting cycles. A fragmented cratonic root underlies the Paraná Basin, with thinner lithosphere along its central rift. High velocities south of the Paraná Block indicate the northern Rio de la Plata Craton’s thick root. The Cenozoic intraplate basalts in the Borborema province, along the southern Atlantic coast and in Paraguay occurred in areas of thin lithosphere and near thick-thin lithospheric boundaries. Most flood basalts of the Phanerozoic large igneous provinces also map on low velocity areas. Smaller flood-basalt portions sit atop cratonic lithosphere and offer new evidence on lateral flow of flood-basalt lava and magma within the crust. About 80 % of known diamondiferous kimberlites are on thick lithosphere, with the exceptions indicating cratonic erosion and thinning since their emplacement
Leveraging Social Media for Geoscience Communication: Insights from the British Geological Survey's Multi-Hazard and Resilience Campaigns
No full textSocial media offers a unique avenue for scientific communication; however, it remains underutilised by many scientific organisations. This study examines the social media strategy of the British Geological Survey (BGS), the UK’s leading geoscience organisation, to assess its effectiveness in engaging the public with research on Multi-Hazard and Resilience. We investigate two key research questions; 1. how effectively does BGS engage the public through its social media efforts, and 2. what challenges does BGS face in using these social media platforms to enhance public understanding?
Scientific organisations often rely on the deficit model of communication, characterised by a one-way transfer of knowledge. Yet, emerging studies suggest that a dialogue-based approach, tailored to different social media platforms and formats, may foster better public engagement. This paper provides a framework for assessing social media activity that can be applied to scientific organisations worldwide.
To address research question 1, we conduct content and sentiment analysis on BGS social media posts – including X, Facebook, LinkedIn, Instagram, YouTube, and BlueSky – from May 2023 to March 2024. A systematic codebook is developed to categorise descriptive and interpretive variables for any social media output. To answer research question 2, we conduct semi-structured interviews with five BGS employees who manage departmental social media accounts to understand their attitudes towards social media engagement.
Our findings suggest several actionable strategies, such as streamlining communication across platforms, maximising the reach of ‘Multi-Hazard and Resilience’ themes, increasing video content output, and better incorporating public feedback. Although focused on BGS, our mixed-methods approach and methodology offer a valuable template for other scientific organisations seeking to enhance their online presence and science communication efforts. This study highlights BGS’s successful establishment of a multi-platform online presence, showcasing a range of content formats that effectively engage audiences
Investigating dusty red supergiant outflows in Westerlund 1 with 3D hydrodynamic simulations
No full textContext. Recent JWST observations towards Westerlund 1 have revealed extensive nebular emission associated with the cluster. Given the age of the region and the proximity of that material to massive stars, it cannot be primordial star-forming gas and the origin is uncertain.
Aims. We aim to determine whether the nebular emission in Westerlund 1 is due to ablation flows from red supergiant (RSG) stars embedded in the cluster wind driven by the Wolf-Rayet stars in the cluster core. We also aim to explore the efficiency of mass loading for the RSG wind in this scenario.
Methods. We used 3D hydrodynamic simulations with the PION code to study the interaction between the cluster and RSG winds. We compared our simulations with the JWST observations by generating synthetic dust-emission maps.
Results. We find that the ablation flow morphology – which shows clumps and instabilities – is consistent with the observations towards Westerlund 1. Synthetic observations at 11 µm predict fluxes in the ablation flow of ~1000–6000 MJy ster−1, which is consistent with the unsaturated components of the JWST F1130W observations in the vicinity of the RSGs in the region. This good agreement is achieved without any consideration of polycyclic aromatic hydrocarbons (PAHs), which have a known 11.3 µm feature that appears in the F1130W band. This suggests that the environment is not conducive to PAH formation and/or the ablation flow is PAH-depleted by wind and radiation action.
Conclusions. Ablation of RSG winds can explain the observed nebulosity in Westerlund 1, at least in the vicinity of the RSGs. Further observations are encouraged to enable detailed studies of these interactions
Thermal emission from bow shocks III: Variable diffuse X-ray emission from stellar-wind bow shocks driven by dynamical instabilities,
No full textContext. X-ray emission from wind-driven bow shocks is both difficult to measure and predict, but may give important insights into the energy budget of the hot phase of the interstellar medium (ISM) by quantifying mixing at the interface between hot and warm gas phases.
Aims. We investigate the effect of magnetic fields and numerical resolution on predicted X-ray emission and other observable properties of bow shocks, to study convergence properties and assess robustness of predicted observables from simulations.
Methods. A suite of 2D and 3D hydrodynamic and magnetohydrodynamic simulations of bow shocks were run and analysed to generate synthetic emission maps and light curves in X-ray and infrared emission.
Results. Resolving the Kelvin-Helmholtz (KH) instability at the wind-ISM contact discontinuity is crucial for obtaining converged results and for predicting X-ray emission and the properties of the hot shocked wind. When sufficient spatial resolution is used, we measure time variation of X-ray emission of at least an order of magnitude on a timescale comparable to the advection timescale of the wake downstream from the bow shock. Good correspondence is found between 2D and 3D simulations with comparable resolution, and 3D simulations can achieve the required resolution with reasonable computing resources. Development of the KH instability is inhibited for shear flows parallel to the ISM magnetic field, compared with what is seen in the perpendicular direction, resulting in synthetic IR emission maps of bow shocks that are smooth when seen from one perspective but show strong distortions from another.
Conclusions. Measuring the X-ray morphology and luminosity in bow shocks may be useful for constraining mixing and energytransfer rates between hot and warm gas phases of the ISM. Dynamical instabilities at the wind-ISM interface are a crucial ingredient in determining the properties of the hot-gas phase in stellar bow-shocks, in particular to capture its time dependence
Waveform tomography of the Antarctic Plate
Full text linkWe present a new seismic shear wave velocity model of the upper mantle of the Antarctic Plate region, AP2024. It includes the lithosphere and underlying mantle down to 660 km depth beneath both the continental and oceanic portions of the plate. To augment the limited seismic station coverage of Antarctica, we assemble very large regional and global data sets, comprising all publicly available broad-band seismic data. The model is built using 785 thousand seismograms from over 27 thousand events and 8.7 thousand stations. It is constrained by both body and Rayleigh surface waves, ensuring the dense data sampling of the entire upper mantle depth range. The tomographic inversion is global but focused on the
Antarctic Plate, with the data sampling maximized in the Southern Hemisphere, with elaborate automated and manual outlier analysis and removal performed on the regional data, and with the regularization tuned for the region. The upper mantle of the Antarctic continent exhibits a bimodal nature. The sharp boundary along the trans-Antarctic mountains separates the cratonic eastern from tectonic western Antarctica and shows a shear-velocity contrast of up to 17 per cent at∼100 km depth. The bimodal pattern is also seen in the oceanic part of the plate, with the older oceanic lithosphere beneath the Indian sector of the Southern Ocean showing higher shear velocities. The continental lithosphere in East Antarctica shows high velocity anomalies similar to those beneath stable cratons elsewhere around the world. It is laterally heterogeneous and exhibits significant thinning in the near-coastal parts of Dronning Maud Land and Wilkes Land. A low velocity channel is observed along the southern front of the West Antarctic Rift System and is probably related to Cenozoic rifting. High seismic velocity anomalies are detected beneath the Antarctic Peninsula and are likely to indicate fragments of
the recently subducted Phoenix Plate Slab. Low velocity anomalies beneath Marie Byrd Land extend into the deep upper mantle and are consistent with a deep mantle upwelling feeding West Antarctica intraplate magmatism
Classification of Bryde’s whale individuals using high-resolution time-frequency transforms and support vector machines
Full text linkWhales generate vocalizations which may, deliberately or not, encode caller identity cues. In this study, we analyze calls produced by Bryde’s whales and recorded by ocean-bottom arrays of hydrophones deployed close to the Costa Rica Rift in the Panama basin. These repetitive calls, consisting of two main frequency components at ~20 and ~36 Hz, have been shown to follow five coherent spatio-temporal tracks. Here, we use a high-resolution time-frequency transform, the 4th-order Fourier synchrosqueezing transform (FSST4), to extract time-frequency characteristics (ridges) from each call to appraise their suitability for identifying individuals from each other. Focusing on high-quality calls recorded less than 5 km from their source, we then cluster these ridges using a Support Vector Machine (SVM) model resulting in an average cross-validation error of ~11% and balanced accuracy of ~86 ±5%. Comparing these results with those obtained using the standard short-time Fourier transform, k-means clustering, and lower-quality signals, the FSST4 approach, coupled with SVM, substantially improves classification. Consequently, the Bryde’s whale calls potentially contain individual-specific information, implying that individuals can be studied using ocean-bottom data
InsituMarine Laboratory for Geosystems Research
Full text linkThe iMARL marine equipment pool , led by the Dublin Institute for Advanced Studies (DIAS), is a significant initiative in oceanographic research, leveraging a diverse array of
ocean sensors for various purposes.
• It comprises broadband Ocean Bottom Seismographs (OBS), acoustic sensors, and sensors for measuring absolute pressure and temperature in the water column.
• The sensor pool is mobile and can be deployed around the world.
• The equipment will allow for the detection of offshore earthquakes and offshore storms, as well underwater noise from vessels and biologically generated acoustic signals
(e.g. from cetaceans).
• Important impacts from this equipment include: natural resources quantification, natural hazard estimation, environmental and baseline climate related “insitu” ocean
monitoring and the monitoring of marine noise pollution
Research Data Management: FAIR
No full textAn Institute level meeting to help initiate collaborative discussions to help map out:
• where DIAS Data management currently stands.
• Ideas, thoughts and plans to catalogue the various research outputs already generated.
• how to proactively address research data management
Predicting near-surface seismic data and velocity models using synthetically-trained deep learning methods: applications in data-rich environments
Full text linkFourier Neural Operators (FNOs) have the potential to offer a deep learning alternative to conventional seismic imaging approaches based on numerical forward modelling and inversion,
with reduced computational cost and several hundred times faster than physics-based solvers after training. Nonetheless, research using FNOs for seismology is still in its early stages. In synthetic volcanic settings to date, FNOs have been applied successfully to both the forward and inverse problem, capturing the fine-scale velocity structure of heterogeneous models. However, to our knowledge, transferring the successful performance of simulation-trained FNOs to field-gathered seismic data is yet to be achieved. In order to accomplish this for volcanological data, training models need to contain representative small-scale velocity heterogeneities and
topography, in order to produce highly scattered codas in the synthetic seismograms. Here we present work in progress on simulation-to-real applications of FNOs using field-gathered
seismic data from offshore sedimentary basin settings as a potential testbed environment. Historical seismic survey datasets from Atlantic sedimentary basins are complemented by
alternative geophysical surveys and site-specific geological constraints. Combining seismic borehole and stratigraphic logs with regional seismic datasets provides a link between field-
gathered seismic waveforms, stratigraphy and depth-dependent, small-scale statistical fluctuations in seismic velocity. This has the potential to enable the creation of synthetic velocity
models and seismograms with field-derived properties, centering the collation of data for real-world machine learning applications in the numerical domain. Future work will apply the insights gained from training FNOs on better understood seismic environments to volcanic contexts
Irish National Seismic Network: An Enhanced Detection Capability
Full text linkThe Irish National Seismic Network (INSN) is operated by the Dublin Institute for Advanced
Studies (DIAS) and co-funded by the Geological Survey of Ireland (GSI). The goal of the INSN is to
monitor seismic activity in Ireland and its near-offshore. Beginning with two stations in 1980, the
INSN expanded its complement to six real-time seismic stations by 2014. From November 2018,
the INSN received funding from the GSI with the aim of doubling the number of operational
seismic stations to twelve.
We describe the methods used in planning the site locations for the new seismic stations, details
on the deployment of test stations and the subsequent data quality analysis. In particular, we
make use of power-spectral density plots, real-time seismic amplitude method (RSAM) and
signal-to-noise ratios of local events. We also describe the layout of the structures housing the
new seismic stations, which include traditional bunker-style designs, as well as shallow borehole
and underground cave installations. We present results of the fully-operational new stations,
highlighting the enhanced detection capability of the network, as well as some examples of
recent observations