Investigation of Depth and Dimension Effects on Ireland’s Karst Aquifers Using Synthetic Seismic Reflected Data

Karst regions are frequently classed as aquifers because they often contain sufficient groundwater to meet various needs. In Ireland approximately 16 percent of public water supply is provided by groundwater resources and karst limestones are important sources of groundwater. There is evidence of karst features (conduits/caves) at depths >100 m below ground level in Irish limestones that can be water bearing. The nature and extent of these types of features are poorly understood, and, to date, deep groundwater resources are largely untapped and uncharacterised. Groundwater exploration and development of these deeper features could be based on 3-D imaging using geophysics to identify potential strategic drilling targets. Karst areas are very difficult environments for any geophysical exploration due to strong lateral and vertical heterogeneity. The main objective of the study is to develop a better understanding of deep groundwater resources in Ireland’s limestones using available seismic datasets. We focus on direct reflection of water filled structures using characteristic seismic feature

Anisotropic Seismic Structure of the Northern East African Rift System and Red Sea from Surface Waves

Continental rifting is a fundamental process of plate tectonics that has been shaping our planet for billions of years. The northern East African Rift system, including the Gulf of Aden and the Red Sea, presents an excellent opportunity to study this process in locations sub -aerially prior to continental break-up, through to full seafloor spreading. We present results from anisotropic surface wave imaging of the region’s crust and uppermost mantle. Anisotropic structures provide additional information about the form of structures at depth and deformation in the region. We find low seismic velocities within the Main Ethiopian Rift (MER), the Red Sea and Gulf of Aden that likely represent melt emplaced in the crust and uppermost mantle. Radial anisotropy, defined as a difference in wave speed of vertically versus horizontally polarized seismic waves, is observed across the region but is strongest within the rift. The strength of radial anisotropy in the MER suggests that horizontally layered melt intrusions are the dominant mode of melt storage in the mid to lower crust. Azimuthal anisotropy, defined as a variation in seismic wave speed as a function of direction, shows complex patterns that are likely related to ancient structures away from the rift, and structures related to extension and melt emplacement within the rift. Taken together, our results suggest melt has played an important role in shaping the crustal structure within the rift and may have also shaped the ancient pre-rift crustal structure

Machine Learning Approaches to Seismic Velocity Model and Seismogram Prediction in Earth’s Shallow Crust

Recent advances in machine learning present new ways for geoscientists to predict geological subsurface properties. Fourier Neural Operators (FNOs) are increasingly being used as an alternative to conventional seismic imaging approaches. FNOs have been shown to predict accurate simulations of seismic waves several hundred times faster than physics-based solvers post-training. In synthetic volcanic settings, FNOs have been applied successfully to both the forward and inverse problem, capturing fine-scale velocity structure in heterogeneous models and seismograms. However, transferring the successful performance of simulation-trained FNOs to field-gathered seismic data is yet to be attained. To achieve this, training models must contain representative small-scale velocity heterogeneities and topography to produce highly scattered codas in synthetic seismograms. This research presents work in progress on simulation-to-real FNO applications using field-gathered seismic data from offshore sedimentary basin settings as a testbed environment. Historical seismic survey datasets from Atlantic sedimentary basins are often accompanied by additional site-specific geological constraints. This makes the creation of synthetic velocity models and seismograms with field-derived properties possible, centering the collation of data for real-world machine learning applications in the numerical domain. The longterm research goal is to bring insights gained from training FNOs on a better understood seismic environment to volcanic and other complex environments in future work

Understanding Unrest and Dynamic Triggering Processes on Sierra Negra, Galápagos Islands

Dynamic earthquake triggering refers to the phenomenon where local seismic activity is induced by dynamic stress disturbances, originating from teleseismic earthquakes. An understanding of dynamic triggering on volcanoes offers a window into volcano stress states and seismicity initiation. Sierra Negra, a basaltic shield volcano situated on Isabela Island, Galápagos, has been the site of recurring episodes of dynamic triggering. Sierra Negra features a large elliptical summit caldera with a trap-door fault system and a magma reservoir extending 2km below the surface. Sierra Negra experienced an eruption in June 2018, characterized by a sequence of pre-eruption inflation, co-eruption deflation, and post-eruption inflation. The occurrence of dynamic earthquake triggering at Sierra Negra was observed in response to high magnitude teleseismic events from 2010 to 2018. The frequency of dynamically triggered earthquakes correlates with the increasing inflation of the magma reservoir. In this study, we aim to answer two questions: 1) How confident are we that the seismicity on Sierra Negra is dynamically triggered? And, 2) What is the location of these dynamically triggered events? Random simulations are used to calculate the likelihood that triggered events are related to teleseismic arrivals rather than being representative of local seismic activity. Results show that pre-2018 eruption, the likelihood that events are dynamic triggering is very high, compared to post-2018 eruption where events are more likely to be representative of local seismic activity. We only have access to a single station (VCH1) on Sierra Negra meaning the single-station location method must be used to locate all dynamically triggered events. To test and refine this method, 79 known seismic events are located using a full network from April 2018 – December 2018. Rotation of the 3-component VCH1 is used to calculate the back-azimuth and the P-wave to S-wave delay is used to calculate the distance between event and station. 21 unknown dynamically triggered events are located in and around the caldera using this method. Looking forward we hope to understand the relationship between the location and timing of dynamic triggering, and its potential use in understanding volcano unrest state

InsituMarine Laboratory for Geosystems Research

The 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

Seismic Tomography of South America: Continental Lithosphere, Subduction-Zone Structures, and the Origins of Intraplate Magmatism

The lithospheric structure of South America records its long and complex tectonic evolution, during which it has influenced the distribution and composition of local magmatism, the geometry of the subduction at its western margin, and the behaviour of the Andean orogeny. Throughout the years, seismic tomography models have provided increasingly accurate images of the Earth’s structure beneath South America. However, our understanding of the upper mantle underlying the continent and its surroundings is still limited by the sparse and uneven distribution of seismic data. In this work, we present a new seismic tomography model of South America and surrounding oceans, including the crust and upper mantle. To address the heterogeneous data coverage in South America, our model SACI-24 (South America Continental Imaging 2024) is based on the inversion of more than 970,000 waveforms from ~300,000 earthquakes, recorded by more than 9000 seismic stations globally and locally. The combined regional and global dataset ensures the densest possible data sampling of the South American continent, its margins, and the surrounding oceans. We invert the waveforms using the Automated Multimode Inversion (AMI) of S-, multiple S-, and surface waves. AMI generates a set of independent linear equations with uncorrelated uncertainties for each source-receiver path. These equations describe the path-average S-wave velocity structure within approximate sensitivity kernels. We assemble these equations into a large linear system and solve it to obtain the 3D distribution of S-wave velocities in the crust, upper mantle, and transition zone. Our model is calculated globally; however, the parametrization and regularisation values are optimized for the South American region, and the data coverage is maximized only in the hemisphere centred on South America. Within the lithosphere, our model reveals a more complex structure of the cratonic lithosphere than previously proposed. Internal heterogeneities within cratonic boundaries include regions of thinner lithosphere, which correspond to areas of proposed rifting in previous tectonic cycles. Inside the boundaries of the Amazon Craton, two distinct cratonic blocks are identified, separated by the Amazon basin. In the São Francisco Craton, newly imaged thin lithosphere underlies the Paleoproterozoic Paramirim Aulacogen area. Our work further reveals separate, high-velocity lithospheric blocks beneath the Parnaíba and Paraná basins. South of the Paraná Basin, our model maps for the first time evidence of the cratonic root of the Rio de la Plata Craton. The detailed mapping of the lithospheric structure reveals its control on several geodynamic processes. Comparison of cratonic lithosphere with the reconstructed position of hotspots reveals that lithospheric thickness is the main control on the distribution of volcanism in large igneous provinces. Under the roots of the Andean Cordillera, our model finds multiple regions of underthrusting of continental lithosphere from South America. Our high-resolution images of the active margin reveal highly heterogeneous subduction, indicating several slab segments from the Nazca and Caribbean plates. East of the Peruvian flat slab, we find areas of thick lithosphere that we attribute to the Amazon Craton, indicating the role of cratonic hydrodynamic suction in flat slab formation. Furthermore, we identify regions under the Altiplano and Puna Plateaus undergoing lithospheric root growth and delamination, indicative of varying stages of Cordillera cyclicity. Within the mantle transition zone, we detect segments of colder mantle from the subduction of the Nazca plate. East of these subduction segments, we identify fast seismic anomalies we interpret as remnants of past lithospheric delamination events. Underlying the thick continental lithosphere, our model reveals prominent low-seismic velocity anomalies extending as deep as the transition zone, with the strongest anomaly found beneath southeast Brazil. Whole-mantle tomography shows that this anomaly extends to a depth of at least 2000 km depth, suggesting a deeply rooted mantle plume. We postulate that interaction with past slab fragments from the long-lived Nazca subduction modifies the plume ascension path, causing it to branch out and travel horizontally to areas of thin oceanic lithosphere, where we find the present-day location of the many hotspots in the Atlantic Ocean

The Global Heat Flow Database: Release 2024

The data publication contains the compilation of global heat-flow data by the International Heat Flow Commission (IHFC; www.ihfc-iugg.org) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI). The presented data update release 2024 contains data generated between 1939 and 2024 and constitutes the second intermediate update benefiting from the global collaborative assessment and quality control of the Global Heat Flow Database running since May 2021 (http://assessment.ihfc-iugg.org). The data release comprises new original heat-flow data published since April 2023 (the update 2023). It contains 91,182 heat-flow data from 1,586 publications. 57% of the reported heat-flow values are from the continental domain (n ~ 54,553), while the remaining 43% are located in the oceanic domain (n ~ 36,692)