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Optimization of Multivariate Linear Regression Model for Ionospheric Disturbed Index

Recent articles in Advances in Space Research - Sat, 03/21/2026 - 19:11

Publication date: Available online 16 March 2026

Source: Advances in Space Research

Author(s): Xiaoxue Min, Cheng Wang

Satellite radar shows Alaska glaciers melt three extra weeks for each 1°C of summer warming

Phys.org: Earth science - Sat, 03/21/2026 - 10:30

Alaska's glaciers respond to climate change by melting for three additional weeks with every 1 degree Celsius increase in the average summer temperature, data from satellite-mounted radars show.

Why some regions are winning the fight against groundwater depletion

Phys.org: Earth science - Fri, 03/20/2026 - 22:00

For half the world's population, the water in their drinking glasses comes from below them. Groundwater also supplies 40% of global irrigation projects. Alarmingly, more than a third of the planet's aquifers, or groundwater basins, are dropping. Declining water tables leave entire regions vulnerable to drought, land subsidence or seawater intrusion while damaging ecosystems and reducing water access. Properly securing this resource is a matter of social, humanitarian and environmental security.

Rivers and tidal currents keep 80% of microfibers from reaching oceans, study suggests

Phys.org: Earth science - Fri, 03/20/2026 - 18:40

Every time we do a load of laundry, tiny fibers of polyester escape from our clothes and slip down the drain. These microfibers, so small they can be invisible to the naked eye, are among the most common forms of microplastic in the ocean. Yet, new research published in Journal of Geophysical Research: Oceans shows that most of them may not make it that far.

The deep freshwater reservoir hidden beneath the Great Salt Lake

Phys.org: Earth science - Fri, 03/20/2026 - 14:40

A potentially huge underground reservoir of freshwater beneath the Great Salt Lake is coming into sharper focus with a new study that used airborne electromagnetic (AEM) surveys to X-ray geologic structures under Farmington Bay and Antelope Island off the lake's southeastern shore.

AI shows promise for flood forecasting and water security in data scarce regions

Phys.org: Earth science - Fri, 03/20/2026 - 09:00

New research reveals that "foundation models" trained on vast, general time-series data may be able to forecast river flows accurately, even in regions with little or no local hydrological records. The approach could improve flood warnings, drought planning and water-resource management in parts of the world where monitoring data is limited.

Seismic attenuation and scattering tomography reveal lithospheric complexity and fluid signatures across the Southern Apennines – Northern Calabrian boundary (South Italy)

Geophysical Journal International - Fri, 03/20/2026 - 00:00

SummaryThe Southern Apennines—Northern Calabrian boundary is a region marked by lithological heterogeneity, complex geodynamics and tectonics, and prone to significant seismic hazard. This sector is part of a complex geodynamic system, where Africa-Eurasia convergence, Ionian subduction, and slab retreat coexist. Its structure and seismic activity derive from extensive lithospheric heterogeneity and fluid-related processes, both of which are poorly constrained. Here, we present a novel application of seismic attenuation and scattering tomography of the area at a regional scale. We estimated seismic wave attenuation and scattering for the Southern Apennines—Northern Calabria region using a dataset of 1581 waveforms related to 95 M ≥ 3.0 earthquakes that occurred between 2004 and 2024 and were recorded at 32 stations. We constrained the heterogeneous properties and fluid saturation of the Southern Apennines—Northern Calabrian region by mapping P-wave Peak Delays and inverting coda-normalized energies for total attenuation (1/Q). Results consistently reveal different seismic energy dissipation mechanisms between the two domains, reflecting their different characteristics in terms of Peak Delay and attenuation patterns. The Southern Apennines exhibit high Peak Delay values at all depths and almost no remarkable total attenuation anomalies, consistent with weakly consolidated, fractured sedimentary sequences and limited fluid content. Nevertheless, at a depth of 5.4 km, a relatively high attenuation pattern is detectable, likely linked to the presence of less cohesive and potentially fluid-saturated units. Conversely, Northern Calabria shows low Peak Delay and high attenuation in the investigated depth range, reflecting wave propagation through coherent crystalline rocks with significant fluid circulation, likely favored by overpressurized materials or active migration pathways. The spatial correlation between high attenuation, low seismic velocities, and thermal anomalies shows that fluids modulate seismic wave behavior, providing new constraints on the crustal structure and seismotectonic segmentation of the region. The joint interpretation of our results with other geophysical models and responses highlights the complex interplay between lithology, tectonics, and fluid dynamics across this critical segment of the central Mediterranean.

Smooth surface reconstruction of earthquake faults from distributed moment-potency-tensor solutions

Geophysical Journal International - Fri, 03/20/2026 - 00:00

SummaryThe earthquake fault as observed by seismic motion primarily manifests as a surface of displacement discontinuity within a linear elastic continuum. The displacement discontinuity and the surface normal vector (n-vector) of this idealized earthquake source are measured by the tensor of potency, which is seismic moment normalized by stiffness. We exploit this theoretical relation to formulate an inverse problem of reconstructing a smooth, three-dimensional fault surface from an areal density field of the potency tensor. In this problem, the surface is represented by an elevation field that parametrizes the vertical variation of the surface relative to a reference, and the nodal planes of a given potency-density-tensor field describe the n-vector field. The remaining subject is the n-vector-to-elevation transform, the operation inverse to defining the n-vector field on a given surface. Whereas this transform is a well-posed one-to-one mapping in two dimensions where the n-vector has one degree of freedom, the transform becomes overdetermined in three dimensions because the n-vector has two degrees of freedom while the scalar elevation has only one, generally admitting no solution. This overdetermination originates from a reduction in degrees of freedom from six to five upon modeling the source as a displacement discontinuity rather than general potency density, namely inelastic strain. The sixth degree of freedom unmodeled by displacement discontinuities and n-vectors manifests as a local violation of the determinant-free constraint in point potency sources; however, in areal sources of potency density, it raises a conflict with the global consistency of the n-vector field. Recognizing that this conflict derives from the capacity of the potency-density-tensor field to describe inelastic strain source incompatible with displacement discontinuity on a surface, we explicitly introduce an a priori constraint to define the fault surface as the smooth surface that best approximates the surface distribution of inelastic strain by displacement discontinuity. We derive an analytical solution for the surface reconstruction thus formulated and demonstrate its ability to reproduce smooth three-dimensional surfaces from synthetic noisy n-vector fields. Lastly, we integrate the derived formula into the potency density tensor inversion and validate it in an application to the 2013 Balochistan earthquake. The estimated fault geometry agrees better with the observed fault trace than that of the previously proposed quasi-two-dimensional surface reconstruction, highlighting the importance of accounting for three-dimensional fault geometry.

Dynamic Lattice Method for Elastic Wave Simulation in 3-dimensional Arbitrary Anisotropic Media

Geophysical Journal International - Fri, 03/20/2026 - 00:00

SummarySimulating the behavior of geological materials represents a fundamental objective in geophysical research. To achieve this goal, various models have been developed for different scenarios. While continuum models based on continuum mechanics are most commonly employed, non-continuum approaches such as the discrete element model and the lattice model have also been developed to address the pervasive discontinuities inherent in geological materials. However, existing non-continuum models are predominantly limited to isotropic conditions, significantly constraining their applicability. The dynamic lattice method proposed in this study aims to overcome this limitation. By independently assigning elastic properties to lattice bonds based on their spatial orientation, we have successfully introduced anisotropy into a three-dimensional lattice model. The linear relationships between the lattice model parameters and their continuum counterparts are established in terms of elastic properties. This advanced three-dimensional lattice model has been effectively applied in elastic seismic wave simulations in arbitrary anisotropic media.