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Balancing Comparability and Specificity in Sustainability Indicators

EOS - Tue, 08/05/2025 - 12:00
Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Community Science

Evaluating progress toward sustainable agriculture is essential for assessing a country’s commitment to sustainability but remains highly complex, particularly given the varying socioeconomic conditions and natural endowments of countries worldwide.

Rich picture created by one of the breakout groups during the stakeholder workshop in Austria. Participants were asked to draw relevant elements of a sustainable agricultural system from the perspective of Austria and then add notes to the existing Sustainable Agriculture Matrix (SAM) indicator wheel with suggestions for relevant sustainability indicators. Credit: Folberth et al. [2025], Figure S15

A recent study by Folberth et al. [2025] represents one of the first attempts to address the critical challenge of balancing global comparability and national specificity in agricultural sustainability indicators. Leveraging the Sustainable Agriculture Matrix (SAM), an indicator system that provides consistent evaluations across countries, the authors co-evaluate the framework with Austrian stakeholders. This process reveals the limitations of current global indicator systems in capturing context-specific social, economic, and environmental nuances.

The study highlights the value of engaging diverse national stakeholders to identify gaps and proposes strategies to regionalize indicators without compromising global coherence. By advancing methods for co-creating regionally tailored frameworks, this research provides a roadmap for enhancing the relevance and applicability of sustainability assessments worldwide.

Citation: Folberth, C., Sinabell, F., Schinko, T., Hanger-Kopp, S., Lappöhn, S., Mitter, H., et al. (2025). Integrating global comparability and national specificity in agricultural sustainability indicators through stakeholder-science co-evaluation in Austria. Community Science, 4, e2024CSJ000092.  https://doi.org/10.1029/2024CSJ000092

—Xin Zhang, Guest Associate Editor, Community Science

Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Demonstration of x-ray fluorescence spectroscopy as a sensitive temperature diagnostic for high-energy-density physics experiments

Physical Review E (Plasma physics) - Tue, 08/05/2025 - 10:00

Author(s): M. J. MacDonald, H. A. Scott, K. H. Ma, S. R. Klein, T. F. Baumann, R. W. Falcone, K. B. Fournier, C. M. Huntington, E. Johnsen, C. C. Kuranz, E. V. Marley, A. M. Saunders, M. P. Springstead, P. A. Sterne, M. R. Trantham, and T. Döppner

We present the use of x-ray fluorescence spectroscopy (XFS) to a sensitive temperature diagnostic in shocked foams at temperatures of 30–75 eV. Cobalt-doped foams were shock compressed using a planar drive at the OMEGA laser facility and photo-pumped with a Zn Heα x-ray source. Analysis of the resul…


[Phys. Rev. E 112, 025203] Published Tue Aug 05, 2025

The 15 July 2025 quick clay landslide at Portneuf in Canada

EOS - Tue, 08/05/2025 - 06:58

A quick clay landslide in the Quebec region has destroyed most of a farm and a local road.

Over the next few days I will try to bring the blog up to date with some of the major landslides that have occurred whilst I have been on leave.

To start, on 15 July 2025 an interesting quick clay landslide occurred at the Rivière-Blanche Est range, in Saint-Thuribe, in Portneuf, Canada. Radio Canada has an excellent piece on this event (in French) that includes images and videos. They have also posted this video (again, in French) that includes some very good aerial imagery of the site:-

This includes the still below:-

The 15 July 2025 quick clay landslide at Portneuf in Canada. Still from a video posted to Youtube by Radio Canada.

The location of this landslide is, I think, [46.69818, -72.15138]. This is a Google Earth image of the site collected in July 2024:-

Google Earth image of the site of the 15 July 2025 quick clay landslide at Portneuf in Canada.

The news reports that I have read do not highlight an obvious trigger for this landslide, but it is interesting to note that the toe is located on the outside of the river bend, where erosion is high. There had been a period of rainfall prior to the landslide, but this does not seem to have been exceptional.

No-one was killed or injured in the landslide, but there is substantial loss of farmland and, in all probability, the farm buildings. The road has also been destroyed. Quick clay landslides are a known hazard in this part of Quebec, but interestingly this site was not classified as being potentially exposed to landslides.

Acknowledgement

Thanks to loyal reader Maurice, and others, for highlighting this event.

Return to The Landslide Blog homepage Text © 2023. The authors. CC BY-NC-ND 3.0
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Storm Floris: The weather is rarely this windy in August, which makes it more dangerous

Phys.org: Earth science - Mon, 08/04/2025 - 19:09
Storm Floris made landfall in northern parts of the UK on the morning of Monday August 4, 2025, bringing intense rainfall followed by severe winds throughout the afternoon. The Met Office issued an amber weather warning for much of Scotland and yellow alerts for parts of Northern Ireland and northern England.

Arctic rivers deliver less vital nitrogen as climate change alters water chemistry

Phys.org: Earth science - Mon, 08/04/2025 - 16:02
Climate change is starving the Arctic Ocean of essential nutrients, with the region's six largest rivers now delivering far less of the type of nitrogen that marine ecosystems need to survive, according to new research in one of Earth's most vulnerable regions.

Ancient alliance between woody plants and microbes has potential to protect precious peatlands

Phys.org: Earth science - Mon, 08/04/2025 - 15:30
As the climate warms and regional drying becomes more frequent, peatlands—some of the planet's most important carbon sinks—are increasingly under threat. But a study led by an international team including scientists from the University of Bristol has shown peatland ecosystems may have a natural defense through the combined forces of plant changes and microbes.

Global benchmarking competition finds shoreline models are ready for real-world coastal planning

Phys.org: Earth science - Mon, 08/04/2025 - 15:14
A UNSW-led global collaborative study has found most shoreline prediction models are effective at forecasting changes to natural, sandy beaches with an accuracy of approximately 10 meters.

Climate change melts nearly 25% of glaciers on pristine sub-Antarctic island

Phys.org: Earth science - Mon, 08/04/2025 - 14:53
Almost a quarter of the glaciers in one of the world's last pristine ecosystems have melted from climate change, according to new research from Monash University.

A new wave in disaster financing: Parametric insurance for tsunami damage

Phys.org: Earth science - Mon, 08/04/2025 - 14:00
If your home was destroyed by a sudden disaster that you couldn't control, you would hope that at the very least, your insurance would cover your losses. However, disaster risk financing systems are struggling to keep pace with growing economic losses. Natural catastrophic (NatCat) events are becoming increasingly costly, and recent global warming could potentially worsen the situation.

NASA-ESA sea level mission could help hurricane forecasts

Phys.org: Earth science - Mon, 08/04/2025 - 13:49
NASA has a long record of monitoring Earth's sea surface height, information critical not only for tracking how the ocean changes over time but also for hurricane forecasting. These extreme storms can cost the United States billions of dollars each year, wreaking havoc on lives and property. Meteorologists have worked to improve forecasts for a hurricane's path, or track, as well as its intensity, measured as surface wind speed. Sentinel-6B, the U.S.-European satellite launching later this year, will help in that effort.

Cave Deposits Reveal a Permafrost-Free Arctic

EOS - Mon, 08/04/2025 - 12:37

About 15% of the land area in the Northern Hemisphere is currently covered by perennially frozen soil known as permafrost. But that has not always been the case. As global temperatures fluctuated in Earth’s past, patches of that frozen soil periodically thawed and refroze.

“Permafrost is a huge reservoir of CO2, and thawing comes with repercussions because it feeds back into future warming.”

A recent study in Nature Communications shows that the Arctic was mostly free of permafrost 8.7 million years ago, when the average global temperature was 4.5°C (8.1°F) higher than it is today.

“Permafrost is a huge reservoir of CO2 [carbon dioxide], and thawing comes with huge repercussions because it feeds back into future warming,” said study coauthor Sebastian Breitenbach, a paleoclimatologist at Northumbria University. Arctic permafrost currently stores twice as much carbon as the entire atmosphere, and because the region is warming faster than the global average, those soils are susceptible to thawing.

In Search of Climate Archives

Breitenbach and his colleagues studied mineral cave deposits from northern Siberia, which is currently underlain by permafrost.

Speleothems such as stalagmites and stalactites form when mineral-rich water percolates through the ground and drips into cave openings, slowly leaving behind calcium carbonate that precipitates out of the water. They can’t grow when the ground above the cave is frozen solid because no water is able to seep through the soil. Any speleothems in the region must have formed when the ground was thawed.

The study was decades in the making. In the early 2000s, Breitenbach and his international group of colleagues were studying caves in a partially frozen region in southern Siberia. At the same time, they were looking for sites with speleothems in the heart of permafrost-covered regions farther north, turning to local communities for information about caves in remote areas. “We started asking hunters, teachers, politicians, bus drivers, anyone who would be out there in the outback,” Breitenbach said. Often, the team would visit a promising area only to find there were no caves there or, when there were caves, no useful speleothems inside them.

“Most of our information for the Miocene comes from marine sediments, so finding good terrestrial archives for this period is fantastic.”

After years of following rumors farther and farther north, they finally struck gold in 2014 at the Taba-Ba’astakh cliffs along the Lena River close to the Arctic Ocean. The team collected 14 speleothems from eroded caves high up in the cliffs and along the beach below.

Using the predictable rate of the decay of uranium into lead and the amounts of each of these isotopes in the samples, the study authors found that the cave deposits were formed 8.7 million years ago, in the late Miocene period.

“Most of our information for the Miocene comes from marine sediments, so finding good terrestrial archives for this period is fantastic,” said Dominik Fleitmann, a geologist and paleoclimatologist at Universität Basel who was not involved in the study. “There are not so many sites because erosion is our enemy. Most of the older deposits are eroded or difficult to date.”

Scientists’ ability to precisely date speleothems makes them incredibly useful as climate records, said Nikita Kaushal, a geologist at the American Museum of Natural History who was not involved with the study. “When you’re looking at past records, you want really good age control on when something happened and for how long, and information on as many climate and environmental parameters as possible.”

By studying the physical and chemical properties of speleothems, scientists can reconstruct the conditions present when the speleothems formed, such as the vegetation cover above, atmospheric circulation changes, local rainfall, droughts, and temperature.

Dima Sokol’nikov surveys a cave in the Taba-Ba’astakh cliffs. Credit: Sebastian Breitenbach

Using the proportions of bonds between certain isotopes, which are affected by the atmospheric conditions present when the mineral-rich water was flowing, the study authors established that average temperatures in the region were between 6.6°C and 11.1°C (44°F and 52°F) when the speleothems formed. That’s about 19°C–23°C (34°F–42°F) warmer than it is today.

Other studies of the same period found that global temperatures were 4.5°C higher than today at the time.

“We know from meteorological data that the Arctic is warming at about 4 times the global average,” Breitenbach said. “The underlying reasons are not entirely clear.” This phenomenon, called Arctic amplification, is likely due to a complex interplay of various factors, including loss of sea ice, air temperature inversion, and ocean heat transport.

A Vulnerable Carbon Pool

As permafrost thaws, the organic matter in the soil begins to decompose, releasing carbon dioxide and methane into the atmosphere. The Intergovernmental Panel on Climate Change estimates 14–175 billion tons of CO2 could be released into the atmosphere by thawing permafrost for every 1°C of global warming.

It’s a process that’s already underway. According to scientists, the upper layers of permafrost were thawing in multiple areas in Svalbard, an archipelago in the Arctic Ocean, in February 2025 as a result of exceptionally high temperatures. The thawing of permafrost is also influenced by several factors beyond temperature, Breitenbach said. “The most important ones are vegetation, snow cover, and wildfire activity.”

Even using conservative estimates, the study authors calculated that the complete loss of permafrost in the Arctic region could release 130 billion tons of CO2 into the atmosphere—and that’s accounting for only short-term emissions from the top 3 meters of thawed soil. “I was quite frightened when I saw these numbers,” Breitenbach said. “4.5° warming is at the extreme end of climate models. It’s not expected to be tomorrow or in the next decades. But even half of this is still drastic.”

Kaja Šeruga, Science Writer

Citation: Šeruga, K. (2025), Cave deposits reveal a permafrost-free Arctic, Eos, 106, https://doi.org/10.1029/2025EO250285. Published on 4 August 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

The State of Stress in the Nankai Subduction Zone

EOS - Mon, 08/04/2025 - 12:00
Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Journal of Geophysical Research: Solid Earth

The Nankai subduction zone, in southern Japan, has hosted several magnitude 8+ earthquakes over the last 300 years, including the 1707 magnitude 8.7 Hōei earthquake, which, until the 11 March 2011 magnitude 9.0 Tohoku-Oki earthquake occurred, was the largest historical earthquake in Japan. The most recent (large) earthquakes in the region were the 1944 magnitude 8.1 Tōnankai Earthquake, followed by the 1946 M8.1 Nankaido Earthquake. Under our current knowledge, the return period of these earthquakes is thought to be approximately 100-150 years.

As a consequence, the Nankai subduction zone is arguably the best instrumented and most extensively studied subduction zone in the world. An important part of this effort has been the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), a major project of the Integrated Ocean Drilling Program (IODP). NanTroSEIZE has spent over a decade drilling, sampling, imaging, and instrumenting this margin to observe and understand the seismogenic and tsunamigenic behavior of an active subduction plate boundary system.

Stress being the driver of faulting, Schaible and Saffer [2025] use data from borehole breakouts, a technique routinely used to infer underground stresses, observed during the NanTroSEIZE experiment. Their analysis focuses on two regions that penetrate major faults along the Nankai Trough: a major out of sequence thrust fault located about 25 kilometers landward of the trench, termed the megasplay (IODP Sites C0004, C0010, and C0022), and the décollement within a few kilometers of the trench (Sites C0006 and C0024).

Their results suggest that while the toe of the prism is understressed, the megasplay fault is near failure. This single result has important consequences for possible mechanical scenarios of how a megathrust earthquake could rupture up-dip all the way to the seafloor surface and, in consequence, on the possible scenarios of earthquake related tsunami generation for southern Japan.

Citation: Schaible, K. E., & Saffer, D. M. (2025). State of stress across major faults in the Nankai subduction zone estimated from wellbore breakouts. Journal of Geophysical Research: Solid Earth, 130, e2024JB030242. https://doi.org/10.1029/2024JB030242

—Alexandre Schubnel, Editor-in-Chief, JGR: Solid Earth

Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Advances in Ecological Forecasting

EOS - Mon, 08/04/2025 - 12:00
Editors’ Vox is a blog from AGU’s Publications Department.

Ecological forecasting is crucial for proactive environmental management and policy-making.

Ecological forecasting is crucial for proactive environmental management and policy-making. In 2001, Clark et al. identified ecological forecasting as an emerging imperative, providing a vision whereby predictions of the future with specified uncertainty enable the anticipation of changes in ecosystems. Ideally, forecasts are then integrated into natural resource decision-making to mitigate adverse effects, enhance resilience, and promote sustainability. Since 2001, the field of ecological forecasting has grown, highlighted by a rapidly increasing number of papers in the literature over time (Lewis et al., 2022).

To highlight both previously published and new research, we, with the support of the Ecological Forecasting Initiative, have launched a special collection titled, “Ecological Forecasting in the Earth System” that showcases advances in the field of ecological forecasting and provides guidance and inspiration for the broader research community.

The special collection brings together cutting-edge research that develops, tests, and applies models to forecast ecological dynamics across systems and scales or advances fundamental frameworks and methods associated with the iterative ecological forecast cycle (Dietze et al., 2018). The ecological systems and scales include marine, freshwater, and terrestrial ecosystems, and dynamics at the population, community, ecosystem, regional, and global scales. Forecasting applications can include, but are not limited to, biogeochemistry, ecohydrology, water quality, phenology, biodiversity conservation, invasive species, vector-borne disease, land-use, and natural climate solutions. 

We are excited to present this joint special collection between the American Geophysical Union (AGU) and the Ecological Society of America (ESA).

To encompass a wide range of environmental disciplines, we are excited to present this joint special collection between the American Geophysical Union (AGU) and the Ecological Society of America (ESA), thereby allowing contributors to submit articles to the journal that is most appropriate for their field. Instead of siloing ecological forecasting in a single journal, we aim to promote the power of forecasting across disciplines, journals, and scientific societies. 

Here, we define ecological forecasts as near-term (i.e., a day to decade ahead) predictions that include estimates of uncertainty (Dietze et al., 2018). Forecasts should be evaluated using data, which can include the use of reforecast analyses (i.e., forecasts of conditions that have already passed but using only model inputs that would have been available if the forecast had been generated in real-time). Forecast uncertainty associated with predictions should be represented and communicated in submitted manuscripts, as absolute knowledge of the future does not exist. Uncertainty can arise from various sources, including the initial starting conditions of a model, model input and drivers (e.g., ensemble weather forecast inputs for an ecological model), model parameters, model structure, and model selection (e.g., multi-model ensembles). In this special collection, if model scenario uncertainty is presented, it should be provided in addition to other sources of uncertainty.

The larger ecological forecasting enterprise encompasses model development, data-model integration, computation, decision support, and education. Manuscripts that are not themselves descriptions and evaluations of ecological forecasts are welcome, provided they highlight direct connections to forecasting. These connections could highlight novel methodologies (e.g., machine learning, process-modeling, uncertainty quantification, digital twins, inverse modeling); interdisciplinary approaches (e.g., co-produced forecasts, integration with decision science, forecast dashboard design, forecast cyberinfrastructure); approaches for forecast delivery and education; and multi-forecast syntheses to enhance the accuracy, uncertainty representation, evaluation, and applicability of ecological forecasts. 

This collection aims to inspire further research and collaboration, ultimately contributing to more informed and effective environmental stewardship.

Overall, this special issue is timely as it coincides with a growing recognition of the need for predictive science in environmental decision-making. By showcasing the latest advancements and applications in ecological forecasting, this collection aims to inspire further research and collaboration, ultimately contributing to more informed and effective environmental stewardship.

The AGU journals included in the Special Collection are Journal of Geophysical Research: Biogeosciences, Journal of Geophysical Research: Machine Learning and Computation, Water Resources Research, Journal of Advances in Modeling Earth Systems, and Journal of Geophysical Research: Oceans. The ESA journals included are Ecology, Ecological Applications, Ecological Monographs, Ecosphere, Frontiers in Ecology and the Environment, and Earth Stewardship.

To submit to an AGU journal please use the standard submission portal for the appropriate journal and select the collection title from the drop-down menu in the Special Collection field of the submission form. To submit your manuscript to an ESA publication, use the standard submission portal and indicate the collection title in the cover letter. Queries to the organizers to share your topic proposal and/or abstract prior to submission are encouraged through our inquiry form.

—R. Quinn Thomas (rqthomas@vt.edu, 0000-0003-1282-7825), Virginia Tech, United States, Associate Editor of JGR: Biogeosciences and special collection organizer; Cayelan C. Carey (0000-0001-8835-4476), Virginia Tech, United States, special collection organizer; Eric R. Sokol (0000-0001-5923-0917), National Ecological Observatory Network, United States, special collection organizer; Melissa A. Kenney (0000-0002-2121-8135), University of Minnesota, United States, special collection organizer; Michael C. Dietze (0000-0002-2324-2518), Boston University, United States, special collection organizer; and Marguerite A. Xenopoulos (0000-0003-2307-948X), Trent University, Canada, Editor-in-Chief of JGR: Biogeosciences

Citation: Thomas, R. Q., C. C. Carey, E. R. Sokol, M. A. Kenney, M. C. Dietze, and M. A. Xenopoulos (2025), Advances in ecological forecasting, Eos, 106, https://doi.org/10.1029/2025EO255024. Published on 4 August 2025. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Tectonic transition in the northeastern Tibetan Plateau: Constraints from InSAR and GNSS measurements

Geophysical Journal International - Mon, 08/04/2025 - 00:00
SummaryThe northeastern Tibetan Plateau is bounded by the left-lateral Altyn Tagh and Haiyuan faults. How crustal motion along these fault systems transitions to crustal shortening and uplift is key for deciphering the geodynamic link between the escape tectonics and the growth of the Tibetan Plateau. Here, we use the PS-InSAR observations, combined with GNSS and leveling data, to obtain a high-resolution 3D model of the present-day crustal motion in the northeastern Tibetan Plateau. The resolved deformation field covers the entire northeastern Tibetan Plateau with a spatial resolution of approximately 0.01° × 0.01 °. Our analysis of slip rates and strain partitioning reveals that crustal motion along the Altyn Tagh fault gradually diminishes eastward and is absorbed by thrusting and uplift in the Qilianshan orogenic belt within the plateau. A similar tectonic transition occurs between the Haiyuan fault and the Liupanshan orogen on the eastern margin of the plateau. Some of the eastward crustal motion is accommodated by the younger Xiangshan-Tianjingshan fault system to the north of the Haiyuan fault, indicating the ongoing northward expansion of the Tibetan Plateau. Our results align with geological evidence of crustal deformation in the past few million years, highlighting the continuing tectonic transition from eastward crustal motion along the left-lateral strike-slip faults to the growth of the Tibetan Plateau.

Expansion of the northeastern Tibetan plateau from surface wave tomography

Geophysical Journal International - Mon, 08/04/2025 - 00:00
SummaryThe continuous NE-SW compression due to the Indo-Asian collision creates active and complex deformation in the northeastern (NE) Tibetan plateau. How the lithosphere of the NE Tibetan plateau deforms both vertically and laterally in response to the ongoing collision is still a question. Further investigations with refined lithospheric structure are required. Here we present a high-resolution radially anisotropic model of the lithosphere beneath the NE Tibetan plateau and surrounding areas that was constrained by the joint analysis of Rayleigh and Love wave dispersion at periods from 6 to 100 s using the methods of ambient noise cross-correlation for short periods and earthquake two-plane-wave for long periods. Results show relatively small regions of significant slow shear wave velocity and positive radial anisotropy (Vsh > Vsv) in the middle crust beneath the Qilian orogenic belt, suggesting the existence of partial melting and probably limited channel flow. Considering the variable lateral strength of shear wave velocity and radial anisotropy in the middle crust with large parts mechanically strong enough to pass the strain, vertical coherent lithospheric deformation could still work in the Qilian orogenic belt. Extensive low shear wave velocity anomaly in the uppermost mantle extend from the Qilian orogenic belt northward to the Alxa block and eastward to the southwestern Ordos block, implying a hot and weak mantle lithosphere. The observed negative radial anisotropy (Vsh < Vsv) in such warm mantle lithosphere beneath the Qilian orogenic belt, Alxa block and the southwestern Ordos block is ascribed to vertical deformation fabrics arising from the convergence between Indian and Asian plates. These observations imply that the lithosphere of Qilian orogenic belt, Alxa block and southwestern Ordos block deform coherently and the NE Tibetan plateau is expanding towards Alxa block and the southwestern Ordos block.

Reconstruction of the autocorrelation function from segmented data and its application to the Earth’s seismic hum

Geophysical Journal International - Mon, 08/04/2025 - 00:00
SummaryWe develop a new method for estimating the autocorrelation function (ACF) from segmented data with the assumption of stochastic stationarity. The ACF of a signal is represented as the summation of the cross terms of sub-segments of arbitrary length. To successfully remove undesired transients in the data, this method introduces a correction for the amplitude bias associated with the removal of sub-segments, based on the comparison between the expected stationary signal and the measured signal. The method reconstructs and accesses later lag times, provides finer frequency resolution, obtains a better signal-to-noise ratio, which enables the extraction of detailed temporal or spectral structures from noisy data sets. As an application, we successfully retrieved a spectrum of the Earth’s seismic hum on the vertical component with fine frequency resolution and compared it to synthetic autocorrelation for spatially isotropic and homogeneous excitation by random shear traction at the ocean bottom and random pressure at the Earth’s surface. Although both models can explain the observed fundamental spheroidal modes, shear traction is better at explaining the observed overtones above 3 mHz. From 2 to 3 mHz, the pressure source also contributes to the excitation of the overtones, and the shear traction becomes dominant again below 2 mHz. This new method is anticipated to be effective in extracting valuable information from rare records within the context of extraterrestrial seismology.

Lithospheric Thermal and Compositional Structure of Northeast China: Implications for Lithospheric Thinning

Geophysical Journal International - Mon, 08/04/2025 - 00:00
SummaryNortheast China, with its complicated regional tectonic evolution, situated within the eastern Central Asian Orogenic Belt, is a key region for understanding lithospheric deformation and mantle dynamics. However, the ongoing debate surrounding its lithospheric structure and evolutionary processes remains, largely attributed to data limitations and methodological constraints. In this study, we integrate topography, geoid height, surface heat flow, and Rayleigh wave phase velocity dispersion curves to conduct a detailed imaging of the lithospheric thermal and compositional structure in Northeast China. We find a significant east-west gradient in lithospheric thickness, ranging from approximately 60 km in the east to 140 km in the west, and a compositional transition in the lithospheric mantle from fertile peridotite in the east to refractory peridotite in the west. By integrating analyses of upper mantle anisotropy and the spatiotemporal distribution of Mesozoic basalts, we argue that the lithospheric delamination and mantle upwelling may have combined to cause the lithospheric thinning in the region. This study highlights the significance of joint inversion of multiple datasets and integrated multidisciplinary analysis.

Experiment of Geopotential Measurement Using GNSS Single-Clock Transportation Method

Geophysical Journal International - Mon, 08/04/2025 - 00:00
SummaryTraditional methods for measuring geopotential difference using optical fiber frequency transfer or satellite-based time-frequency transfer, based on general relativity, require the use of two clocks and the calibration of these clocks. Here we present a simplified clock transportation experiment using a single hydrogen clock to measure the geopotential difference between two time-frequency stations, separated by 129 km with a height difference of 1,245 m, by GNSS precise point positioning time-frequency transfer. Taking the reference clock of International GNSS Service (IGS) time as a ‘bridge’, we extract the gravity frequency shift between the two stations by comparing the fractional frequency differences between the hydrogen clock and the ‘bridge’ before and after clock transportation. The determined geopotential difference between the two stations is 12075.9$\pm $118.5 m²/s², which closely aligns with the value computed by the EIGEN-6C4 global gravity field model, with a difference of -78.7 m²/s². These results validate the feasibility of geopotential difference measurements with a single clock and highlight several advantages compared to the dual-clock method: elimination of inter-clock calibration, low operational complexity and equipment cost, high data utilization efficiency but similar precision of geopotential difference measurement. Furthermore, this method can be extended to other similar techniques to measure geopotential differences, provided that they enable users to connect to a stable time-frequency reference.

Earthquakes in the Weiyuan area in China: insights from numerical simulation

Geophysical Journal International - Mon, 08/04/2025 - 00:00
SummaryShale gas extraction could produce underground stress perturbation and local seismicity, which could put a threat human casualty. The Weiyuan area in the Sichuan province, China, underwent massive gas production and a significant increase of earthquake since 2015. In this study, we focus on human-induced subsurface hydrofracturing, calculate cumulative underground Coulomb-stress changes using a 3D numerical model, and probe the main cause of recent seismic activity in the Weiyuan area based on continuous regional stress/displacement loading. The simulation reveals the regional extent of positive Coulomb stress change with fractures matches the distribution of the moderate and micro seismicity in the past ten years. Background regional tectonic stress in the vicinity of the active fault likely resulted in earthquake preparation within and around the active faults; hydraulic fracturing changes mainly the displacement and stress pattern in the vicinity of the fracturing wells, and enhanced fracturing intensity (fracture volume-to-model volume ratio (θ), causes more obvious difference; faults may be locked prior to fracturing, and even small fracturing intensity may trigger the earthquakes near faults and fracturing wells; the seismic risk will be significantly increased near the two faults and fracturing wells in the next 50 years.

Satellite data reveals 15-year trends in forest carbon storage worldwide

Phys.org: Earth science - Fri, 08/01/2025 - 13:59
Forests play a central role in the global carbon cycle as trees store carbon in their trunks, branches, roots and leaves. However, climate change and human activities can change the ability of forests to absorb carbon and the annual changes in these carbon stocks are highly variable in space and time around the globe. That's why having continuous observations of the evolution of forest biomass over a long period is important for monitoring this essential climate variable.

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