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Ultralow Velocity Zones at the Core-Mantle Boundary in the Subduction Regions Consistent with the Iron-Rich Origins Revealed by ScP Waveform Complexities

Geophysical Journal International - Thu, 02/19/2026 - 00:00

SummaryUltralow velocity zones (ULVZs) at the Earth’s core-mantle boundary (CMB) are marked by substantial reductions in seismic velocities. They are often associated with significant increases in density, providing important insights into deep Earth composition and dynamics. In this study, we investigate ULVZs beneath eastern and southern Asia, regions associated with long-term subduction, by analyzing high-frequency (~1 Hz) ScP waveforms recorded at the small-aperture KZ array. After correcting for attenuation along the ScP path, we perform a grid search to match the observed waveform complexities with synthetics generated for a comprehensive suite of 1D ULVZ models. The best-fitting models for each event constrain ULVZ thickness, P- and S-wave velocity reductions, and density anomalies, revealing widespread but laterally variable ULVZ structures, although the influence of finite ULVZ geometry cannot be entirely excluded. The correlations among these parameters point to iron-rich chemical heterogeneity as the dominant origin of the imaged ULVZs, likely reflecting iron enrichment associated with long-term subduction processes.

Unlocking the potential of single stations to replace seismic arrays

Geophysical Journal International - Thu, 02/19/2026 - 00:00

SummaryWe introduce Virtual Seismic Arrays, which predict full array recordings from a single reference station, eliminating the need for continuous deployment of all stations for continued array operation. This innovation can reduce costs and address logistical challenges while maintaining multi-station functionality. We implement a Virtual Seismic Array using a deep learning encoder-decoder approach to predict the transfer of the seismic wavefield between stations. We train on recordings of secondary ocean microseisms from the Gräfenberg array in Germany to retrieve predictive models for each array station, which together form the Virtual Seismic Array. To evaluate its performance, we beamform original and predicted waveforms to detect the dominant secondary microseism sources. We assess three source regime scenarios: one where only a single dominant source regime is present in both the training and test dataset, another with two different regimes in the training data but only one in the test data, and a third where the training data does not contain the dominant source regime observed in the test data. Our results show strong agreement between predicted and original beamforming results in cases where the observed source regime was part of the training, demonstrating the feasibility of Virtual Seismic Arrays.

Antarctic warming is altering atmospheric stability: New evidence from the 1950s to the present

Phys.org: Earth science - Wed, 02/18/2026 - 23:00

A new study published in the Journal of Climate reveals how surface warming in Antarctica, particularly over the Antarctic Peninsula, is significantly altering the stability of the lowest layers of the atmosphere.

'Boomerang' earthquake simulations suggest ricocheting ruptures may be more common than previously thought

Phys.org: Earth science - Wed, 02/18/2026 - 22:40

An earthquake typically sets off ruptures that ripple out from its underground origins. But on rare occasions, seismologists have observed quakes that reverse course, further shaking up areas that they passed through only seconds before. These "boomerang" earthquakes often occur in regions with complex fault systems. But a new study by MIT researchers predicts that such ricochet ruptures can occur even along simple faults.

New study identifies sequence of critical thresholds for Antarctic ice basins

Phys.org: Earth science - Wed, 02/18/2026 - 19:38

The Antarctic ice sheet does not behave as one single tipping element, but as a set of interacting basins with different critical thresholds. This is the finding of a new study by the Potsdam Institute for Climate Impact Research (PIK) and the Max Planck Institute of Geoanthropology (MPI-GEA). With today's warming, about 40% of the ice stored in West Antarctica may already be committed to long-term loss, while parts of East Antarctica could cross thresholds at moderate levels of warming between 2 to 3°C compared to pre-industrial levels, contributing significantly to global long-term sea-level rise.

Mantle plume vs. plate tectonics: Basalt cores reshape the North Atlantic breakup debate

Phys.org: Earth science - Wed, 02/18/2026 - 19:23

About 56 million years ago, Europe and North America began pulling apart to form what became the ever-expanding North Atlantic Ocean. Vast amounts of molten rock from Earth's mantle reached the ocean floor as the crust stretched and thinned, creating a volcanic, rifted margin between Norway and Greenland, a marine feature that has intrigued scientists for decades.

Understanding 'Snowball Earth' extreme climates when the world is covered in ice

Phys.org: Earth science - Wed, 02/18/2026 - 19:14

In the whole history of Earth's climate, few events are as extreme as those that geologists call "Snowball Earth."