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Seismic waves produced by thunderstorms, called thunderquakes, can be used as a novel source for seismic imaging, according to a new study led by researchers at Penn State.

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From 2020 to 2022, California faced one of its driest periods on record, in part because of human-caused climate change. Though the drought has eased, scientists have noticed lasting effects on the state’s aquifers that may affect their ability to store water in the future.

A new study published in the Proceedings of the National Academy of Sciences of the United States of America found that the drought and resulting overpumping of groundwater caused some aquifers in the Sacramento Valley to collapse and become irreversibly damaged. The study is the first to capture this kind of aquifer collapse in high-resolution satellite data and provides evidence in support of giving the Sacramento Valley’s aquifers additional protections, the authors write.

“How fast part of the Sacramento Valley is subsiding was quite surprising to us,” said Stacy Larochelle, a geophysicist at the University of California, Los Angeles, and lead author of the new study. “This is really one of the first times we could capture this transition in so much detail.”

“It’s sad that the Sacramento Valley is seeing more subsidence, but that it’s being recognized, documented, and looked at in more detail is a good thing,” said Claudia Faunt, a retired hydrologist at the U.S. Geological Survey California Water Science Center who was not involved in the new study.

Sinking Sacramento Valley

Larochelle did not set out to measure the drought’s impact on Sacramento Valley aquifers. Rather, she noticed a periodic trend in regional Global Navigation Satellite System (GNSS) data, which track ground deformation using fixed, ground-based instruments. The data showed that aquifers were being depleted and refilled at a regular, seasonal pace from 2016 to 2020. She noticed a striking change around 2021, when parts of some aquifers suddenly sank.

Wanting more information, Larochelle and the research team looked to interferometric synthetic aperture radar (InSAR) data, which track land surface deformation over time using radio waves sent from satellites. InSAR data, GNSS data, and groundwater monitoring wells all showed the same pattern.

When humans pump groundwater out of an aquifer, they remove water between the aquifer’s rocks and sediment. This removal creates empty space, and the aquifer shrinks. Usually, this process is elastic: Once the aquifer fills with water again, the spaces between the rocks and sediment swell, and the aquifer rebounds.

“You have a permanent collapse of the pore space.”

But if too much water is removed too rapidly, the structure of the aquifer’s sediment deforms irreversibly, and it loses its ability to recharge and store water in the future. “You have a permanent collapse of the pore space,” Larochelle said.

When water was removed during the 2020–2022 drought, for example, some areas of the Sacramento Valley subsided at rates up to 30 centimeters per year, enough to damage the aquifer’s infrastructure.

The end of the drought and influx of strong precipitation events in 2023–2025 have not returned these damaged aquifers to their former state, though researchers say more study is needed. “From preliminary observations, we don’t see a huge rebound,” Larochelle said. “We’re not seeing a full recovery; we’re not seeing the ground go back up.” She said she does not expect some parts of the aquifers to ever recover.

In the long term, that means the aquifer will not be able to store as much water for future generations, which could also increase flood risk as the ground is unable to absorb as much precipitation.

Protecting Aquifers

In 2014, California’s Sustainable Groundwater Management Act (SGMA) created statewide regulations guiding groundwater pumping. Water managers designated many basins in the San Joaquin Valley, adjacent to the Sacramento, as “critically overdrafted,” changing the basins’ monitoring requirements. (The Sacramento and San Joaquin Rivers interact with their valleys’ aquifers in complex ways. Though river flow is one indicator of the health of an aquifer, the California Department of Water Resources mainly monitors groundwater flow from wells.)

The Sacramento Valley, drained by the Sacramento River, is the northernmost part of California’s large Central Valley aquifer. It borders the San Joaquin River Basin, which has many “critically overdrafted” subbasins (colored in red). Click image for larger version. Credit: California Department of Water Resources

“Maybe we should change the designation of the Sacramento Valley,” Larochelle said, “so that we’re as careful in the way we extract groundwater from it as we are with the southern part of the valley.”

Faunt agreed, saying that the California Department of Water Resources should determine if changes to SGMA classification are warranted in areas where scientists are beginning to see a permanent loss of storage. “The authors have a point,” she said.

The team’s methods also provide a way to track the impacts of groundwater pumping on aquifers in real time using satellite data. Such tracking could give communities an early warning that they’re pumping too much groundwater, before an aquifer is irreversibly damaged, Larochelle said. Though that’s not a completely new idea, Faunt explained that using InSAR data, GNSS data, and ground-based data all together in one method is a newer approach that helps scientists see how the different types of data align or diverge.

Another of the study’s findings was that most of the ground-based groundwater monitoring data in the Sacramento Valley are for shallow parts of the region’s aquifers. That disparity indicates a need to monitor all levels of an aquifer to be able to gather a three-dimensional picture of which layers are being affected by pumping, Faunt said.

The study could also help scientists better measure aquifers without ground monitoring data, Larochelle said. California has one of the best groundwater monitoring systems in the world, so using a combination of satellite data and ground-based measurements there can help calibrate satellite measurements in other parts of the world that may not have a dense network of ground-based instrumentation.

“That’s the dream, long term,” Larochelle said. “To be able to just use satellites to see what’s going on in the groundwater system.”

—Grace van Deelen (@gvd.bsky.social), Staff Writer

Citation: van Deelen, G. (2026), California’s drought irreversibly damaged Sacramento Valley aquifers, Eos, 107, https://doi.org/10.1029/2026EO260267. Published on 21 August 2026. Text © 2026. 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.

Jennifer Bhatnagar spent the summer of 2023 traversing barren hillsides blackened by wildfire in northern California. She walked through devastated properties, examined the hot soil beneath her feet, collected samples and asked questions.

SummaryAmbient noise based monitoring of subsurface velocity changes is possible without the explicit retrieval of Green’s functions by correlation. Velocity variations can directly be observed from the fluctuations in the spectrograms of ambient noise time series or their cross-spectra. This approach is more resource efficient than the conventional Green’s function based monitoring and ideally suited for edge processing and the analysis of large volumes of data for example from fibre-optic records. The spectral fluctuations result from wave propagation in the heterogeneous subsurface and interference between different scattering paths. The fluctuations are directly related to the occurrence of coda waves in the Green’s function. In contrast to coda wave interferometry in the time domain, monitoring the evolution of spectral fluctuations allows for measurements of velocity changes that are unbiased by changes in the source spectrum. Recognizing that the imprint of the subsurface heterogeneity is directly encoded in the spectral fluctuations opens a new perspective on the investigation of subsurface scattering and attenuation.

SummaryWe develop a discrete event modeling framework that captures the progression of geophysical systems toward catastrophic failure through sequences of distinct damage events. By representing geophysical system evolution as a succession of temporally accelerating and amplitude-varying events, the framework reveals how finite-time singularities, both logarithmic and power law types, naturally emerge from the interplay between shrinking interevent intervals and growing event magnitudes. This event-based perspective, which can be viewed as a discrete representation of progressive damage accumulation in heterogeneous geomaterials, provides an intuitive physical understanding of rupture processes, highlighting how precursory signals such as accelerating strain rate, event frequency, and energy release can be traced back to simple underlying mechanisms. A mean-field damage-based formulation further links the observed power law exponents to the evolving stiffness of the geophysical system under constant or time-varying stress. Incorporating stochastic fluctuations, the model captures the inherent randomness of natural systems leading to the emergence of stochastic finite-time singular behavior. Together, these results establish a simple yet powerful framework for interpreting the dynamics of catastrophic events, providing a common event-based perspective on observations from landslides, glacier breakoffs, volcanic eruptions, and other related processes, and strengthening the physical foundations of early warning and hazard forecasting.

SummaryThe Accurately Controlled Routinely Operated Signal System (ACROSS) is an artificial seismic source that generates highly repeatable and stable seismic waves for high-resolution temporal monitoring. While direct P- and S-waves from ACROSS have been widely used to monitor earthquakes, volcanic activity, and environmental changes, the scattered waves that arrive later, known as coda waves, have received limited attention. In this study, we used coda waves generated by ACROSS to monitor subsurface seismic velocity changes (dv/v) over 10 months. The ACROSS signals were recorded by a seismic array of 14 seismometers deployed approximately 3 km from the source in Morimachi, central Japan. By deconvolving the records with a known source function, we obtained transfer functions corresponding to band-limited Green’s functions. Coda wave interferometry applied to the coda portions of these transfer functions detected temporal variations in dv/v, exhibiting both seasonal long-term variations and rainfall-induced short-term variations. Comparative analyses using direct P- and S-wave travel-time changes from the same ACROSS data and ambient-noise interferometry show that, under the present observational conditions, these conventional methods primarily detect long-term variations; however, they do not resolve the rapid, transient short-term variations. In contrast, the stable ACROSS source combined with the broader sampling of coda waves provides superior sensitivity to environmental changes across both timescales over kilometer-scale distances, highlighting its effectiveness for high-temporal-resolution monitoring. To investigate the mechanisms responsible for the observed dual-timescale variations, we used a poroelastic model with precipitation input and considered thermoelastic effects and groundwater-induced changes as possible contributors to the long-term variations.

Offshore wind farms are a key pillar of the energy transition. The European Union plans to expand offshore wind capacity in the North Sea by 2050. A new study by the Helmholtz-Zentrum Hereon indicates that a very extensive expansion could influence regional precipitation patterns: While precipitation over the sea could increase, it could decrease in coastal regions.

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Earlier this year, NASA announced that one of its powerhouse telescopes, the Neil Gehrels Swift Observatory, was falling from orbit much faster than anticipated. Although Swift’s low-Earth orbit had remained relatively steady for more than 2 decades, unusually strong solar activity in 2024 destabilized it. The agency predicted that the telescope would burn up in Earth’s atmosphere by the end of 2026.

NASA soon after announced a commercial effort by U.S. company Katalyst Space Technologies to rescue the telescope by using another spacecraft to boost Swift’s orbit. The mission launched successfully on 3 July. However, after a month of technological issues with the rescuing craft’s maneuvering thrusters, NASA and Katalyst have pulled the plug on the mission, leaving Swift to its fiery fate.

 
Related

•  FAQ About Swift
•  About the rescue mission attempt
•  NASA Updates Next Steps for Commercial Swift Boost Mission
 

“This is not the outcome we were working toward, but it does not change why this mission was worth attempting,” NASA administrator Jared Isaacman said in a 19 August statement. “The team moved with extraordinary speed to give Swift a chance to carry out more science while advancing capabilities America will need for satellite servicing in the future.”

Swift launched in 2004 with the goal of monitoring unpredictable high-energy astrophysical phenomena called gamma-ray bursts. The mid-sized mission operates out of a small building near Pennsylvania State University in State College with the picturesque Allegheny Mountains as a backdrop.

The telescope was designed with the ability of spotting these short-lasting explosions and quickly pivoting to monitor the events and their aftermaths in multiple wavelengths. But during its 21 years of science operations, Swift became a workhorse of multiwavelength astronomy observations, studying everything from the active centers of distant galaxies to supernovae near and far, as well as ravenous black holes, brown dwarfs, and interstellar objects. Take a look back at some of its most notable discoveries.

The BOAT: Over and over since its science operations began, Swift announced the detection of powerful gamma-ray bursts that shattered previous records, including the brightest of all time (BOAT). Since launching in 2004, it has made 829,336 observations and spotted more than 1,800 gamma-ray bursts.

Left: Swift has detected nearly 2,000 gamma-ray bursts since its launch in 2004. Credit: NOIRLab/NSF/AURA/M. Garlick, CC BY 4.0

Interstellar Object Chemistry: Swift also observed objects much closer to home, though these objects had distant and exotic origins, too. In 2019, Swift’s ultraviolet instrument detected water coming off of the interstellar object 2I/Borisov. In 2025, it performed similar observations of the interstellar comet 3I/ATLAS.

Right: Swift detected the presence of outgassed water coming from interstellar comet 2I/Borisov. Credit: NASA, ESA, and D. Jewitt (UCLA)

“Rosetta Stone” Supernova: In 2008, Swift spotted an X-ray burst in galaxy NGC 2770. It turned out to be the precursor to a supernova, spotted in an earlier stage than ever before. Because of Swift’s rapid response, astronomers around the world could observe the supernova throughout its evolution in multiple wavelengths. With so many types of observations of a single event, SN 2008D has been called the “Rosetta stone of supernova studies.”

Left: Some supernovae detected by Swift resulted in magnetars. Credit: NASA E/PO, Sonoma State University, Aurore Simonnet

Black Holes Snacking on Stars: When a star gets too close to a black hole, the black hole’s gravity can break the star apart into a stream of gas. The black hole can gobble up the gas and burp out some intense radiation. In 2023, Swift observed one black hole repeatedly taking bites out of an unlucky star that ventured too close. Every few weeks the black hole—with the mass of a whopping 200,000 Suns—swallows three Earth-masses of material from the star and belched out x-rays.

Right: Swift observed bursts of energy as a black hole snacked on a star. Credit: NRAO/AUI/NSF/NASA

Brown Dwarf Wandering By: Swift joined forces with NASA’s Spitzer Space Telescope in 2016 to observe a microlensing event, which occurs when a close-by passing object distorts the light coming from a more distant one. With this technique, Swift helped discover a brown dwarf 80 times the mass of Jupiter that orbits close to a Sun-like star. Swift and Spitzer’s discovery, OGLE-2015-BLG-1319, is one of the few brown dwarfs found to orbit their host stars within a few Earth-Sun distances.

Left: Swift aided in the discovery of a rare brown dwarf using gravitational microlensing. Credit: NASA/JPL-Caltech

Milky Way Magnetars: When some stars die they become small, dense balls of neutrons with extremely intense magnetic fields. These magnetars can release short, strong bursts of energy as they interact with surrounding material. Swift has studied many of these magnetars, including one that hid in the center of the Milky Way and masqueraded as our galaxy’s supermassive black hole, and another one surrounded by a “wind nebula.”

Right: Magnetars can release intense bursts of radiation, which have been picked up by Swift. Credit: ESO/L. Calçada, CC BY 4.0 Science After Swift

Swift launched with a nominal mission lifetime of 2 years. It has lasted nearly 22 years, and yet its demise will leave a gaping hole in NASA’s ability to study the high-energy universe. Although NASA said that it would “continue to prioritize finding new options to react readily to cosmic events,” no telescope in NASA’s current or upcoming portfolio will look at the universe at the same wavelengths as Swift or with the same ability to monitor unexpected transient events.

“We knew this was a high-risk, high-reward [rescue] mission—a first-of-its kind attempt, developed on an unprecedented timeline driven by the Sun’s activity,” Shawn Domagal-Goldman, director of NASA’s Astrophysics Division, said in a statement. “We were all hoping for more science from Swift. But we knew the takeaways from this mission would be worthwhile either way.”

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

These updates are made possible through information from the scientific community. Do you have a story about science or scientists? Send us a tip at eos@agu.org. Text © 2026. AGU. 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.

Over the past 230,000 years, the growth and retreat of the Icelandic ice sheet have led to major changes in the seawater chemistry of the North Atlantic, caused by the interaction between volcanism and ice in Iceland. Scientists at the Institute of Environmental Physics at Heidelberg University have demonstrated this using sediment cores from the northeastern Atlantic—the Rockall Plateau.

A new study published in Communications Earth & Environment, with contributions from researchers at the Leibniz Centre for Tropical Marine Research (ZMT), shows that higher seawater temperatures could significantly reduce the long-term ability of underwater plants to store carbon.

Extreme precipitation events are among the most damaging natural disasters and a major concern in our changing climate. In the U.S., since 1980, the most destructive events alone have caused more than 2,800 deaths and $700 billion in damages. But what is the total area of the country affected by these events each year? And how have these patterns changed over the past several decades? In a recent study in Geophysical Research Letters, led by researchers at Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School, the authors discovered some unexpected trends.

Methane-munching microbes in soil might be more important than previously thought, a new study finds. Soil is an important carbon sink, and scientists are still learning much about the diversity of its microbial communities. They're being uncovered from Arctic soils to desert sands, and some of them are sucking down methane—a greenhouse gas about 27–30 times more potent than carbon dioxide over 100 years.

Firefighters have been battling a vast wildfire in the hills above Blaenavon in south Wales, spreading across more than 4,000 hectares (9,900 acres), for three weeks.

Dense evergreen plantations in Canada's boreal forest absorb so much winter sunlight that the resulting surface warming can offset 6% to 20% of the climate benefit they are credited with. Canada's current carbon accounting frameworks measure the carbon stored but largely omit the heat absorbed by these forests, according to a new policy brief from the United Nations University Institute for Water, Environment and Health (UNU-INWEH). The result is inflated mitigation estimates and public investment in forests that may not deliver the cooling they promise.

As competition between the United States and China intensifies over critical minerals, pressure is mounting to begin exploitation of deep-sea minerals before a code to regulate mining of the seabed in areas beyond national jurisdiction is agreed to.

Source: Journal of Geophysical Research: Biogeosciences

Methane-munching microbes in soil might be more important than previously thought, a new study finds. Soil is an important carbon sink, and scientists are still learning much about the diversity of its microbial communities. They’re being uncovered from Arctic soils to desert sands, and some of them are sucking down methane—a greenhouse gas about 27–30 times more potent than carbon dioxide over 100 years.

Soil methanotrophs are organisms capable of biologically removing methane from the atmosphere. Current estimates vary widely, but soil methanotrophs may store an average of 28–35 gigatons of methane per year globally. And even that could be an underestimate, scientists suspect.

Previous efforts to estimate the global biological methane source from wetlands and inland fresh waters primarily used process-based modeling, which focuses on biogeochemical processes, and atmospheric inversion modeling, which starts with methane concentrations in the atmosphere and works backward to determine emission sources.

But estimates from these two approaches tend to differ. The bottom-up, process-based estimates of methane emissions from wetlands and inland fresh waters were higher than the top-down, atmosphere-based estimates. A larger soil sink could help offset some of these discrepancies, bringing net bottom-up estimates closer to those inferred from the atmosphere.

Oh et al. dig in to reconcile that discrepancy and refine the estimate of how much methane-munching soil microbes contribute to the global methane sink.

The authors added a third kind of modeling: data-driven machine learning. By running the three kinds of models in parallel and comparing their results, the researchers hoped to home in on a more reliable estimate with smaller uncertainties. They also tweaked the microbial dynamics in the process-based model and included previously overlooked places and microbes.

The three-pronged approach worked. Both process-based and machine learning models yielded similarly sized sinks. According to their estimates, microbes in soils take up 40–45 gigatons of global methane per year, significantly higher than estimates from older approaches. That value is also larger than estimates in global climate assessments, such as that of the Intergovernmental Panel on Climate Change. When incorporated in top-down atmospheric inversions, this larger soil methane sink also improved the models’ ability to reproduce observed atmospheric methane and its stable carbon isotope composition.

The findings suggest that the microbial soil methane sink has been underestimated and that the revised three-model approach may improve global carbon cycle modeling. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2025JG009668, 2026)

—Rebecca Dzombak, Science Writer

Citation: Dzombak, R. (2026), It takes three to model methane right, Eos, 107, https://doi.org/10.1029/2026EO260268. Published on 20 August 2026. Text © 2026. AGU. 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.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Tectonics

The Eastern and Southern Alps deform slowly compared with many tectonically active regions worldwide, making their ongoing movements especially difficult to detect. Grützner et al. [2026] provide an unusually detailed synthesis of decades of research across nine countries, combining evidence from different datasets, methods, catalogues, and research traditions. By comparing and reconciling these sources, the study creates a comprehensive framework for understanding how active faults and earthquakes relate to climate, the structure of Earth’s outer rocky layer, and deeper processes within the planet.

The results show that present-day deformation is controlled mainly by a strong crustal block beneath the Dolomites pushing into the Alps, movement between relatively rigid blocks of rock, and uplift as the land rebounds following the melting of ice-age glaciers. The slow movement of hot mantle rock deep within Earth appears to play a smaller role than previously proposed. The areas of greatest earthquake hazard are concentrated along the southern edge of the Alps and where the Alps meet the Dinarides. This synthesis will provide an important reference for researchers studying the Alps and other slowly deforming regions, where weak tectonic signals and varied datasets make earthquake-hazard assessment particularly challenging.

Citation: Grützner, C., Petersen, G., Serpelloni, E., Metzger, S., Moernaut, J., Ustaszewski, K., et al. (2026). Active tectonics of the eastern and southern Alps – Crustal response to deep processes? A review. Tectonics, 45, e2025TC009267. https://doi.org/10.1029/2025TC009267

—Lothar Ratschbacher, Associate Editor; and Djordje Grujic, Editor, Tectonics

Text © 2026. 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.

Global mangrove cover—vegetation vital to tackling climate change—has increased over the past 40 years, despite significant losses in some key regions, according to a new analysis.

At least 107 people were killed in major failure at an artisinal mine on the border with Cameroon.

In the afternoon of 18 August 2026, a large landsldie occurred at an artisinal gold mine at Zamboye (also spelt Zamboï) in the Central African Republic. The landslide was caught on videos that have been widely shared (there are two different angles). Please be aware that it makes uncomfortable viewing:-

I am unsure of the precise location of this accident. It is described as being close to Garoua-Boulaï, which is located at [5.888, 14.550].

News reports indicate that 107 bodies have been recovered to date, but that the toll might be higher.

At first sight, the behaviour of the miners looks odd – there is a huge crowd directly in the path of what is clearly an unstable slope. I suspect though that the videos capture just one of a series of failures. This screenshot is from early in the recorded failure sequence:

Screenshot of the video of the 18 August 2026 gold mine landslide at the Zamboye (Zamboï) mining site in the Central African Republic.

It appears to me that this landslide moves onto, and mobilises, debris from an earlier failure, which can be seen in the bottom right hand corner of the image. I would speculate that the failure event(s) captured in the videos might be just one of a series of failures.

Were the crowds trying to rescue people already buried when this recorded landslide occurred?

Of course, this serves to remind us of the horrific dangers faced in artisinal mines, such as the one at Zamboye.

Return to The Landslide Blog homepage Text © 2026. The authors. CC BY-NC-ND 3.0
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Photovoltaic technology, most commonly seen as bulky solar panels used on solar farms, is expected to become a dominant energy source by 2050. But these panels are often installed on land that might otherwise be used to grow crops and feed a burgeoning population.