SummaryGlaciers are key components of the global climate system and sensitive indicators of environmental change. Their dynamics generate diverse seismic signals, whose source mechanisms offer valuable insights into their internal stress conditions. While moment tensor inversion has been applied to icequakes on a few alpine and polar glaciers, it had not yet been implemented on the Argentière Glacier (French Alps). In this study, we conduct a systematic characterization of icequake source mechanisms based on a dense dataset of 14 057 near-surface events recorded by 98 3-component sensors deployed at the surface of the glacier during the RESOLVE project. We apply a full waveform inversion method to jointly reconstruct the moment tensor and the source time wavelet for each event. The moment tensor Green’s functions used in the inversion are computed through numerical modeling of elastic wave propagation in a 3D medium, incorporating real surface topography. This approach allows us to exploit the full complexity of the recorded seismic signals and to move beyond previous analysis based on simplified models and single-component data. The results reveal a clear dominance of opening-type (tensile crack) mechanisms, consistent with extensional stress regimes at the crevasse locations, with principal stress direction almost perpendicular to the local crevasse orientations. The exceptional size of the catalog enables a detailed investigation of spatial patterns in source mechanisms, particularly highlighting structural complexity in the heavily crevassed downstream zone. The distribution of extensional and compressional mechanisms further indicates a highly heterogeneous stress field at the glacier surface, influenced by local crevasse geometry. Depth-dependent variations in the reconstructed moment tensors suggest that deeper events tend to involve more isotropic components, likely reflecting pressure-driven failure under overburden stress. These findings demonstrate the potential of full waveform inversion to characterize the source mechanisms associated with the icequakes on a glacier. This work represents a significant step toward integrating seismological modeling with glaciological interpretation in alpine environments.
Communities worldwide rely on reservoirs for drinking water, hydroelectric power, irrigation, and more. These critical freshwater resources are affected by seasonal and long-term changes; water levels in reservoirs can dip during hot summer months or due to prolonged drought, or can flood after a particularly strong storm. Despite their importance, there are key gaps in our knowledge of reservoir structure and dynamics. Two recent papers published in Scientific Data use Landsat data to help fill in those gaps.
The circular economy concept is often thought of as a model to eliminate waste and pollution—but when applied thoughtfully, circular approaches can create jobs, strengthen local economies, improve public health and more, according to new research led by Charles Darwin University (CDU).
As global temperatures climb, rainfall patterns are shifting in ways that could put water resources and agriculture under increasing strain, a new study published in Water Resources Research suggests.
Scientific expeditions require months of planning before scientists can acquire the first data. A bark cuts through the Arctic silence, waking Anna up. She slept only three hours after collecting the last sample. Anna reaches for her rifle, exits the tent, and steps onto the midnight ice. She pets the guard dog she rented a few days earlier. It might be a false alarm, but she scans the darkness for polar bears, hoping her training pays off. She cannot afford to lose the samples. Nor her life.
SummaryKinematic characteristics (creeping or locked) and high-precision seismic catalogs can constrain the shallow (<20 km) slip pattern of active fault zone. We collect Sentinel-1 Synthetic Aperture Radar (SAR) images and extract a high-resolution deformation velocity field along the active Laohushan-Haiyuan (LHS-HY) fault zone in the northeastern margin of the Qinghai-Tibet Plateau. We invert the shallow fault coupling and slip distribution using two-dimensional (2D) and three-dimensional (3D) models, indicating that the fault zone exhibits an alternating pattern of large strong coupling asperities and creeping zones, and the deep slip rate decreases from 5.2 mm/yr in the west to 3.4 mm/yr in the east, accompanied by a transition from strike-slip to dip-slip components. Then we calculate cumulative seismic energy release, seismic slip rate, and statistical parameters including $b - \textit{value}$, coefficient of variation of seismicity interevent times, and Nearest-Neighbor Distance (NND) with regional seismic catalog. The geodetic and seismic results demonstrate a complex shallow slip pattern in the fault zone. The following characteristics are highlighted. A significant throughgoing locked-creeping transition zone with variable depth range extends from the eastern part of the Laohushan segment (LHS) to the eastern segment of Haiyuan Fault (HYE). A shallow (<6 km) creeping zone with weak coupling and seismicity in the western HYE segment differs from the shallow part of the locked-creeping transition zone between the eastern LHS segment and the western part of the western segment of Haiyuan Fault (HYW). A transition zone with strong coupling and active seismicity in the eastern HYE segment ranges from 4 km to 12 km in depth. The results provide new insights into the shallow slip behavior of the LHS-HY fault zone, and offer valuable references for seismic hazard assessment in the region.
SummaryAccurate sensor orientation estimation is critical for reliable seismological processing, especially when rotating three-component seismograms is required. In this study, we determine the sensor orientation angles of 676 broadband stations of ChinArray-II deployed in northeastern Tibet between August 2013 and June 2016. The polarizations of both Rayleigh waves and teleseismic P-waves are used to estimate the azimuthal deviation. The results demonstrate that both approaches are consistent and approximately 600 stations are well-aligned, with mis-orientation angles less than 10°. The remaining stations exhibit various orientation problems, such as vertical component reversal and temporal variations in sensor alignments. Moreover, detailed multi-event analysis reveals that three-component sensor gain discrepancies may lead to failures of both P- and Rayleigh-wave approaches, while post-validation of multi-event estimation can identify such issues. Compared with previous studies, our results provide comprehensive sensor orientation information and indicate that combining noise level and wave polarization yields robust estimations.
SummaryThe South Peru subduction zone is a complex, highly active region, which has hosted four Mw 8 + earthquakes over the last 100 years. It marks the transition between the flat slab associated with the Nazca Ridge subduction in the North and more steeply dipping subduction in the South, causing the slab to contort and affecting seismicity patterns in the region. In this study, we present the first high-density, high-quality seismic catalog of the region between the arc and the trench, totaling 166 825 events between January 1st 2022 and December 31st 2024, including 125 467 well-located ones. We first picked and associated phases using PhaseNet and PyOcto, then located the resulting events with NonLinLoc-SSST and GrowClust3D. Finally, we derived a new slab model from the seismicity, allowing us to classify the earthquakes as upper plate (16 per cent), interface (12 per cent), lower plate (68 per cent), outer rise (0.20 per cent) and human-related (3.1 per cent).The region is broadly divided into four subregions with different seismicity patterns and slab geometries: the flat slab, with intense interface and intraslab activity, the slab transition zone, where the plate contorts to accommodate its change in geometry, the Arequipa region, with intense upper plate seismicity but very low intraslab and interface seismicity, and the North Chile region, with a large band of dense intraslab seismicity.We find that in the flat slab region, the Nazca Ridge is linked to the presence of dense seismicity close to the trench, and seismic swarms hinting at the presence of slow slip. Meanwhile, the intraslab seismicity in that region is organized in trench-parallel bands which are likely related to slab bending. In the slab transition region, we image multiple orthogonal faults just south of the slab contortion, suggesting a damaged slab. Further south, in the Arequipa region, upper plate seismicity forms a large, trenchward-dipping structure seemingly connected to the Incapuquio fault at the surface. Finally, in North Chile, the deep band of intraslab seismicity appears to locate further downdip as we move to the north, perhaps reflecting changes in slab properties.
In recent years, the Prairies have seen bigger swings in climate conditions—very wet years followed by very dry ones. That makes an already unpredictable landscape even harder to forecast, with real consequences for flood preparedness and water quality.
Wild animals are not just inhabitants of the natural world. Many also act as natural landscape engineers, reshaping Earth's surface as they burrow, feed, and build shelters that move soil and sediment across ecosystems. From animals disturbing riverbeds to burrowing species redistributing soil, wildlife constantly modifies the physical structure of landscapes through everyday activities.
SummaryThe Orientale Basin is the youngest and best-preserved multi-ring impact basin on the Moon. It is approximately 930 km in diameter and comprises three concentric rings—the Cordillera, Inner Rook, and Outer Rook rings. We used Gravity Recovery and Interior Laboratory (GRAIL) mission gravity data (GRGM1200B, truncated to degree 660) to invert the three-dimensional (3D) density structure associated with the basin’s mascon and ring-related crustal anomalies. To separate longer and shorter-wavelength signals, we performed inversions using (1) spherical harmonic degrees 2–660 to characterise the basin’s deep structure and (2) degrees 60–660 to highlight crustal-scale heterogeneity. The inversion with degree and order of 2–660 resolves a basin-wide central positive density anomaly beneath the inner depression, extending from a depth of ∼16–80 km, corresponding to uplifted mantle. This anomaly persists below the crust–mantle boundary; however, its deep continuation should be interpreted cautiously because it may partially reflect vertical smearing in the gravity inversion. Nonetheless, the spatial association of this anomaly with a mascon rooted in the upper mantle is compatible with impact-driven uplift of dense material from depth, followed by post-impact thermal evolution and relaxation processes. The inversion with degree and order of 60–660 indicates alternating positive and negative density anomalies associated with the ring system. Prominent ring-parallel positive anomalies occur along the Outer Rook Ring and Cordillera Ring, extending to ∼30–35 km depth and exhibiting a density contrast of ∼60–200 kg/m3. The geometry and lateral continuity of these anomalies across multiple rings support an interpretation of ring-controlled crustal heterogeneity, consistent with either intrusion and structurally focused modification along ring-related discontinuities or impact-generated fracturing that provided pathways for magma ascent. The results of this study provide quantitative constraints on the depth, magnitude, and spatial distribution of density anomalies associated with the Orientale mascon and ring system, thereby improving the subsurface framework for regional geological interpretation and supporting future lunar landing-site geophysical investigations and in situ sampling. Based on the inferred crustal density architecture, we propose that future geophysical sampling efforts should prioritise the Outer Rook Ring and Cordillera Ring, where the observed ring-parallel anomalies may provide insights into crustal modification processes and the composition of the lunar interior.
SummaryWe studied ionospheric changes associated with the 2025 March 28 Myanmar earthquake (Mw7.7) using global navigation satellite system receivers to measure ionospheric electrons, as a part of the project to predict earthquake precursors. The total electron contents above the fault changed their trends ~36 minutes before the earthquake, with the positive anomaly reaching ~1 per cent of the background. These quantities fit well with the past ~20 cases despite relatively large day-to-day variability due to high geomagnetic activities. The positive anomaly was sandwiched by two negative anomalies to the north and the south, suggesting within-ionosphere electron transportation along geomagnetic fields possibly driven by surface positive electric charges released from the fault.
SummaryWe develop and demonstrate a new paradigm for modeling prompt forensics data from potential nuclear explosions of concern. Related scenarios include nuclear terrorism, which may involve low-yield detonations. Traditional modeling appropriate for higher-yield historical nuclear testing is generalized to capture uncertainties in yields (such as when using conversion to obtain “equivalent” nuclear yields for conventional explosives in low-yield experiments) and to capture variation among source-to-sensor path effects for which no calibration data are available. Special attention is paid to quantifying these sources of uncertainty and to their formal inclusion in comprehensive yield uncertainty — uncertainty that would otherwise be underestimated and potentially lead to mistaken conclusions. For the example scenario considered, two useful stand-alone monitoring phenomenologies are based on geophysical data (from surface effects characteristics and local seismic metrics). By fusing signatures from multiple phenomenologies, the Multi-Phenomenology Explosion Monitoring (MultiPEM) framework provides improved yield characterization relative to reliance on single-phenomenology analysis alone, especially when individual sensors have complementary sensitivities to emplacement/environmental conditions.
Abstract
To meet the high-precision and high-integrity positioning demands of safety–critical applications, monitoring the quality of precise satellite products in global navigation satellite system (GNSS) precise point positioning (PPP) is crucial. This work employs ionosphere-free (IF) PPP with ambiguity resolution (PPP-AR) phase residuals to construct test statistics for monitoring the quality of precise satellite corrections. By utilizing precise satellite orbit and clock products from CODE, WUM, and GRG, the PPP-AR phase residuals were first analyzed with sample moments, Allan variance and power spectral density (PSD). The key findings are as follows: (1) The skewness and kurtosis results indicate that ambiguity-fixed phase residuals deviate from an ideal zero-mean Gaussian distribution and exhibit a super-Gaussian distribution. (2) Allan variance and PSD analysis reveal that flicker noise dominates the phase residuals. (3) The noise amplitudes are similar for all satellites, but certain differences are observed among different GNSS systems and satellite types. (4) The noise level of phase residuals is influenced by the receiver types, antenna types, and precise products from different analysis centers. Leveraging the error characteristics, the two-step Gaussian overbounding (OB) method was employed to estimate the corresponding OB parameters of the phase residuals. The overbounding results demonstrate that, under similar conditions, phase residuals can be bounded by the calculated bound within the acceptable integrity risk after removing the detected outliers. Anomaly monitoring experiments further show that phase residuals can effectively capture anomalies in precise satellite corrections, with the set threshold successfully detecting such anomalies.
The measurement of virtual height of the sporadic E layer (h'Es) is very sensitive to the type of ionosonde used and the calibration processes. The ionosondes used by the national institute of communication an...
Abstract
Solar photospheric abundances and CI-chondrite compositions are reviewed and updated to obtain representative solar system abundances of the elements and their isotopes. The new photospheric abundances obtained here lead to higher solar metallicity. Full 3D NLTE photospheric analyses are only available for 11 elements. A quality index for analyses is introduced. For several elements, uncertainties remain large. Protosolar mass fractions are H (X = 0.7060), He (Y = 0.2753), and for metals Li to U (Z = 0.0187). The protosolar (C+N)/H agrees within 13% with the ratio for the solar core from the Borexino experiment. Elemental abundances in CI-chondrites were screened by analytical methods, sample sizes, and evaluated using concentration frequency distributions. Aqueously mobile elements (e.g., alkalis, alkaline earths, etc.) often deviate from normal distributions indicating mobilization and/or sequestration into carbonates, phosphates, and sulfates. Revised CI-chondrite abundances of non-volatile elements are similar to earlier estimates. The moderately volatile elements F and Sb are higher than before, as are C, Br and I, whereas the CI-abundances of Hg and N are now significantly lower. The solar system nuclide distribution curves of s-process elements agree within 4% with s-process predictions of Galactic chemical evolution models. P-process nuclide distributions are assessed. No obvious correlation of CI-chondritic to solar elemental abundance ratios with condensation temperatures is observed, nor is there one for ratios of CI-chondrites/solar wind abundances.
The January 2022 Tonga volcanic eruption generated atmospheric pressure waves that propagated over the ocean’s surface and triggered a meteotsunami. This meteotsunami caused significant amplitudes exceeding 10...
Abstract
Accurately modeling and prediction the nonlinear motion of GNSS (Global Navigation Satellite System) coordinate time series holds significant theoretical and practical value for the study of geodynamics. A novel integrated network, named Ensemble Learning method based on Signal Source Driver (ELSSD), is proposed, which leverages the strengths of Long Short-Term Memory (LSTM) and Deep Self-Attention Neural Network (DSANN), while integrating GNSS loading data as an additional data source. Additionally, a multi-track synchronous sliding window data processing strategy is designed to address the challenge of multi-source data fusion input. The effectiveness of this algorithm is validated using GNSS coordinate time series from 186 global stations over a period of 10 years. Experimental results initially illustrate that, when accounting for displacement caused by environmental loading effects, there is a marked improvement in the modeling and prediction accuracy compared with GNSS input-only. Furthermore, the application of three ensemble network strategies-Bagging, Boosting, and Stacking-have further been demonstrated to enhance modeling and prediction accuracy. Compared with LSTM and DSANN networks, the proposed ELSSD algorithm achieves an average RMSE (Root Mean Square Error) of 3.6 mm for both modeling and prediction, with modeling accuracy improvements of 4.8% and 6.2%, while prediction accuracy improvements of 5.4% and 5.9%, respectively. With respect to the traditional Least Square method, there is an improvement of 22.1% and 27.9% in modeling and prediction accuracy, respectively. Regarding noise characteristics, there is a significant reduction in colored noise amplitude, with decreases of 36.7% and 36.0% observed in modeling and prediction, respectively. Simultaneously, the velocity uncertainty experiences an average reduction of 27.1% and 27.5%. The average velocity differences are measured at 0.06 mm/year and 0.24 mm/year, respectively. Hence, our findings suggest that the ELSSD algorithm emerges as an effective methodology for handling multi-source data input in GNSS coordinate time series, presenting promising practical applications in the field.
The Mw 7.5 Noto Peninsula earthquake, which occurred on January 1, 2024, was considerably hazardous to the peninsula and surrounding regions owing to a strong motion, large-scale crustal deformation, and subse...
Nature Geoscience, Published online: 21 February 2025; doi:10.1038/s41561-025-01653-z
Quartz-rich clasts in Martian meteorite NWA 7533 indicate the presence of granitic rocks on early Mars that formed via hydrothermal activity and impact melting, according to petrologic and in situ geochemical analyses.
