SummaryThe Ojos del Salado Volcano, the highest active volcano in the world, is located at the southern end of the Puna plateau in central Chile. Here, the subduction angle of the down-going Nazca plate shallows, causing volcanism to move inland marking the southern end of the Central Andean Volcanic Zone (CAVZ). Little is known about the current volcanic activity at this southern edge or the dominant crustal stresses at these volcanic centres. In this study, we use a temporary network of 29 geophones to record local seismicity at the Ojos del Salado volcano. The type of seismic event, number of events per day, location, and magnitudes of events all provide insight into the structure, material properties, and activity level of the volcano. Between February 6th and 28th 2024, this network recorded 93 events with local magnitudes larger than 0, the largest having local magnitude 2.8. The events formed two main clusters, one on the western flank of Ojos del Salado itself near the summit, and a smaller cluster to the north. Most events in the northern cluster occurred within a 35 minute seismic swarm on February 8th. Twenty-one fault plane solutions were determined for events within the network. Six of these occurred during the northern swarm and showed steep oblique faulting and fifteen in the summit cluster, which mainly show normal faulting with strikes comparable to E-W oriented mapped faults in the area. Fault plane solutions at both clusters indicate a north-south extensional stress state. This agrees with the regional stress axes of the southern Puna plateau found in other studies, suggesting that the local crustal stresses at the Ojos del Salado volcano mainly follow the regional stresses with some variation in fault planes near the summit and in the northern swarm that could be due to locally high magmatic or geothermal fluid stresses. Heavy rain in the days preceding the northern swarm may have increased the amount of fluid available, potentially inducing the swarm on February 8th. No seismicity was observed near the Laguna Verde, or the two smaller volcanoes within the network: the Barrancas Blancas and Mulas Muertas. Ojos del Salado is therefore the main source of seismic activity and likely heat source within the study area. The level of seismicity and the occurrence of a seismic swarm to the north and five small seismic swarms near the summit suggest that there is still volcanic activity at Ojos del Salado and it could benefit from monitoring.
Publication date: Available online 5 March 2026
Source: Advances in Space Research
Author(s): Shipra, Debabrata Banerjee, Shiv Kumar Goyal
Publication date: Available online 5 March 2026
Source: Advances in Space Research
Author(s): Hematollah Roradeh, Komeil Abdi
The Miocene, beginning approximately 23 million years ago, represents a canonical "warm-Earth" interval characterized by elevated atmospheric CO2 and a warmer global climate. The El Niño–Southern Oscillation (ENSO), as a leading mode of interannual climate variability, exerts pronounced influences on global precipitation patterns and the occurrence of climate extremes. Investigating ocean–atmosphere variability under Miocene-like high-CO2 background states therefore provides a valuable framework for evaluating climate-model performance in warm climates and for informing expectations of ENSO behavior under continued anthropogenic warming.
The episode of extreme rainfall that affected the east of the Iberian Peninsula at the end of October 2024 left a devastating mark on the province of Valencia. In some areas, such as Turís, more than 700 liters per square meter were recorded in 24 hours; in other words, in just one day, more water fell than the average rainfall in mainland Spain in an entire year. This caused catastrophic flooding and the disaster resulted in more than 200 deaths, as well as billions of euros in damage.
Ice cores taken from glaciers reveal the air pollution of the past, using atmospheric particles incorporated in snow that fell on the glacier and became ice. Now, scientists have extracted a record of thousands of years' worth of air pollution from 9.5 meters of ice at the Weißseespitze glacier, close to the border between Austria and Italy. But this ice is under threat from global warming, and scientists warn that it is now a race against time to capture critical climate information locked in these glaciers before it's gone forever.
SummaryThe eastwards extrusion of Tibetan Plateau (TP) materials has led to complex tectonic deformation and frequent seismicity in the western Sichuan Basin (SCB). To elucidate crustal deformation mechanisms and seismogenic structures, we inverted broadband (3–60 s) Rayleigh wave dispersion curves using ambient noise tomography from 448 stations and constructed a 3-D S-wave velocity (Vs) structure for the upper to middle crust beneath the SCB and adjacent regions. Our model revealed a thick, low-velocity sedimentary layer within the SCB that extends to 15 km depth along its northwestern margin, likely resulting from the accumulation of eroded materials from surrounding orogenic belts. The three-dimensional velocity model resolved sedimentary cover thicknesses ranging from 6 to 13 km within the basin and yielded average Vs values of 3.08, 3.17, and 3.25 km/s for Mesozoic, Palaeozoic, and Proterozoic strata, respectively, thereby calibrating the basement burial depths of major geological units in the sedimentary layers. Notably, this study identified deep low-velocity anomalies beneath the Dayi seismic gap (DSG) and segmented velocity structures along the Kangding–Shimian section, providing crucial deep structural constraints for evaluating the seismogenic environment and future earthquake hazards of major seismic gaps in the Sichuan–Yunnan region. The velocity structure clearly delineates the formation and evolutionary characteristics of multiple foreland basin development episodes since the Late Triassic, offering important constraints for understanding the deep structure of the SCB, assessing seismic hazard risks, and guiding petroleum resource exploration.
SummaryHigh-resolution P-wave velocity tomography of the Japan subduction zone down to 700 km depth is determined by conducting a joint inversion of arrival-time data of local earthquakes and teleseismic events, which were recorded at land-based Hi-net seismic stations and seafloor S-net stations. Our inversion results show the high‐velocity subducting Pacific slab and low‐velocity zones in the mantle wedge beneath active arc volcanoes. Subslab low-velocity anomalies (SLVAs) are revealed in the mantle below the Pacific slab, which may reflect hot and wet mantle upwelling derived from return flow associated with the slab deep subduction. The SLVAs at depths of ~150-260 km exhibit a bimodal distribution, where interplate slow earthquakes occur. There is a SLVA gap below the mainshock hypocenter and rupture zone of the great 2011 Tohoku-oki earthquake (Mw 9.0). The SLVAs may influence the megathrust segmentation by their buoyancy, heat, and melt, and so affect the generation of megathrust and intraslab earthquakes. These results shed new light on the structural heterogeneity and mantle dynamics of the Japan subduction zone.
SummaryThe cycle-skipping problem that plagues full waveform inversion (FWI) can be at least partially mitigated if low frequencies (which encode the kinematics of wave propagation in seismic data) are recorded. However, seismic sources and receivers are band-limited, so seismic data doesn’t generally include signals down to 0 Hz. To improve our ability to solve the seismic inverse problem, one can synthesize this missing low-frequency (LF) content from the recorded high-frequency (HF) data using machine learning (ML) models. Deep learning models such as convolutional neural networks (CNNs) demonstrate impressive ability to perform low frequency extrapolation. However, such models require powerful hardware (GPU machines) and careful training. We assess the extrapolation capabilities of three different ML models that do not require GPU machines, namely, random forest, Gaussian process regression, and gradient boosting, on both synthetic and real data. Experimental results on two synthetic datasets (generated from a low velocity lens embedded in a homogeneous medium, and the Marmousi model) demonstrate that FWI applied to the extrapolated data consistently improves inversion accuracy relative to FWI applied to the original datasets that do not contain low frequencies. Application of low-frequency extrapolation to real data from the Northwest Shelf of Australia demonstrates that tree-based ML models such as gradient boosting can outperform CNNs in terms of both accuracy and computational cost on non-GPU architectures.
SummaryThis study quantifies the spatial heterogeneity of nonlinear signals, background noise, and vertical velocities in GNSS vertical time series across the Tibetan Plateau (TP), using multi-source loading corrections to isolate tectonic deformation. We analyzed 20 years of GNSS data (2002–2021) from CMONOC and NGL networks, processed via GipsyX and referenced to ITRF2014. Non-tidal atmospheric (NTAL), oceanic (NTOL), and hydrological (HYDL) loading effects were applied utilizing operational models from GFZ and GRACE mascon data (CSR/JPL/GSFC), followed by common mode error (CME) filtering. The findings highlight significant spatial heterogeneity: Monsoon-dominated southern TP exhibits 10–20 per cent RMS reduction after non-tidal atmospheric-oceanic (AO) loading corrections, while northern TP shows minimal improvement (<10 per cent), highlighting non-atmospheric noise dominance. Integration of AO and GRACE-modeled hydrological (AOG) loading corrections outperform soil moisture-based models (AOH), achieving 25–35 per cent RMS reduction in glacier-covered Himalayas by resolving cryospheric mass loss. Spectral and principal component analysis (PCA) analyses confirm AOG’s superiority in suppressing interannual signals (PC1 variance: 62.7 per cent vs. AOH’s 60.3 per cent), particularly in monsoon-ENSO-affected regions. Noise modeling demonstrates high spatiotemporal correlations (63.1 per cent WN + FN in raw data), with flicker noise (FN > 5.2 mm) linked to seismic activity in southeastern TP and power-law noise (PL > 3.5 mm) to permafrost dynamics in the north. Post-AOG_CME processing simplifies noise structures (WN + GGM dominance: 32.9 per cent), reducing velocity uncertainties by 26.9 per cent and revealing a residual + 1.2 mm/yr uplift in the southern inner TP, indicative of mid-crustal flow. Persistent uncertainties (>0.55 mm/yr) along the Himalayan thrust front correlate with deep lithospheric boundaries. Our findings demonstrate the necessity of integrating GRACE-derived corrections with CME filtering to accurately delineate tectonic signals within the intricate suture zones of the TP, offering crucial insights into plateau-wide geodynamic processes.
SummaryEarthquake ground motion is strongly influenced by near-surface geology, which governs its amplification, duration, and spatial variability. Under intense shaking and depending on the material strength, sediments often exhibit nonlinear behaviour, producing large deformations that reduce shear-wave velocity, shift resonance frequencies, and increase damping. We analyse over two decades of borehole-surface recordings from 28 stations in Iwate Prefecture, Japan, collected by the Kiban Kyoshin network (KiK-net), to quantify these effects. Frequency-domain analysis (stacked Stockwell power spectral density) and time-domain interferometric methods (multitaper deconvolution and phase cross-correlation) provide consistent results, revealing systematic decreases in both resonance frequency and seismic velocity with increasing peak ground acceleration (PGA). Frequency shifts inferred from the surface data mainly reflect the shallowest layers, whereas velocity changes estimated with borehole-referenced methods capture a path-averaged perturbation between the surface and borehole sensors and therefore depend on borehole depth. The data set is divided into seven PGA bins based on surface recordings, with the 1-5 cm s−2 bin serving as a baseline for comparison, representing linear site conditions. Across all stations, relative velocity reductions average ∼ 12 per cent in the 200-400 cm s−2 PGA range, corresponding to a shear modulus reduction (μ/μ0) of about 23 per cent. Nonlinear effects are most pronounced at sites with thicker sedimentary deposits, which are mainly found in the central valley and northern foothills of Iwate Prefecture. In contrast, VS30 shows no clear correlation with the observed nonlinearity, as its averaging effect masks thin low-velocity layers near the surface that are prone to nonlinear response during strong shaking. These results underline that nonlinear site response is highly site-specific, and that large observational data sets are crucial for robust characterisation across a seismic network.
SummaryThe Xianshuihe-Xiaojiang Fault System (XXFS), with slip rates of centimeters per year, is a major tectonic boundary accommodating southeastward extrusion of the Tibetan Plateau. Stretching over ~1,000 km through the densely populated Sichuan and Yunnan provinces in western China, it is particularly important to evaluate its potential for generating destructive earthquakes. This study systematically evaluates the XXFS within a physically grounded probabilistic framework by integrating geodetically modeled interseismic coupling, seismicity, empirical magnitude-area scaling laws, and barrier effects of creeping zones during dynamic rupture. We assess a range of rupture scenarios and obtain most probable maximum magnitudes of Mw 7.4 for the Xianshuihe fault, Mw 7.3 for the Anninghe-Zemuhe Fault, and Mw 7.2 for the Xiaojiang Fault, with corresponding fault-level recurrence of ~300, ~1 500 and ~170 years. The probabilities of occurrences of Mw 7.0 earthquake are higher along the northern and southern Xianshuihe, southern Anninghe, northern Zemuhe, and southern Xiaojiang segments. By assimilating geodetic and seismic data into a probabilistic framework that incorporates moment balance and rupture dynamics, our study provides a physics-based foundation for assessing regional seismic hazard in this tectonically active area. The approach is generalizable and can be applied to other fault systems where seismicity, basic geometry and geodetic coupling are constrained.
Climate change is lengthening our days because rising sea levels slow Earth's rotation. Researchers from the University of Vienna and ETH Zurich now show that the current increase in day length—1.33 milliseconds per century—is unprecedented in the past 3.6 million years. The team reconstructed ancient day-length fluctuations using the fossil remains of single-celled marine organisms known as benthic foraminifera.
Thanks to upstream diversions and climate change, Utah's Great Salt Lake has shrunk by 70% since 1989, exposing about 800 square miles of playa and mudflats—along with numerous curiosities. While a potential environmental catastrophe, the lake's dewatering presents numerous research opportunities for University of Utah geoscientists, including several who are looking to characterize the extent, characteristics, chemistry and flow of a mysterious, mostly freshwater aquifer under the playa.
The Amazon rainforest is famous for storing massive amounts of carbon in its trees and soils, helping regulate the global climate. Yet a paper published in New Phytologist shows that one of South America's largest carbon-storing ecosystems exists in an often-overlooked grassy savanna: the Cerrado in Brazil.
Before rain begins to fall, scientists and engineers can predict where a storm might cause flooding thanks to advanced modeling and digital simulations that help guide billion-dollar decisions involving infrastructure design, emergency response, land-use planning, insurance, agriculture, water quality, and public safety.
SummaryFrom late-December 2024 to mid-March 2025, a 50-km-long dyke intrusion triggered over 300 earthquakes (magnitude 4 to 5.9) between Fentale and Dofen volcanoes along the Northern Main Ethiopian Rift. Dyke intrusions periodically occur along the Fentale-Dofen magmatic segment and are an expression of ongoing rift extension. Preliminary analyses using interferometric synthetic aperture radar revealed extensive ground deformation (up to 60 cm), which closely matched the temporal and spatial evolution of surface manifestations and earthquake locations from global catalogs. While global catalogs are critical for real-time monitoring, the precision of locations in remote and or sparsely instrumented regions can be low. In this investigation, we present surface-wave relocation results of the dyking episode that began near Fentale volcano in December 2024. We estimate relative locations using differential travel times measured from regional-to-teleseismic distance surface-wave observations of earthquakes reported by the U.S. Geological Survey. Relative relocations reduce the initial region of diffuse seismicity to a 50-km-long narrow band bounding the strike of surface manifestations and the zone of maximum surface deformation. We demonstrate the precision of surface-wave relocations over incremental time periods, capturing the progression of dyking from seismic onset through seismic migration and caldera subsidence. Results showcase the utility of surface-wave relocations in the characterization of dyking episodes and provide complementary insights into the current understanding of the Fentale-Dofen volcanic plumbing system.
Artificial intelligence is rapidly transforming weather prediction, enabling forecasts that once required hours of supercomputing time to run in just minutes. But as AI tools play an expanding role in high-stakes hazard modeling, researchers at Rice University say an essential question remains: Do AI-generated storms behave realistically?
Two new studies conclude that stabilizing long-term climate risks will require sustained net-negative carbon dioxide (CO₂) emissions for centuries. Approaching the problem from distinct perspectives—legal and technological feasibility on the one hand, and economic optimization under uncertainty on the other—the research converges on a consistent message: reaching net zero is not enough.
Publication date: Available online 5 March 2026
Source: Advances in Space Research
Author(s): Shagun Aggarwal, Andrew Dempster, Jason Held
