Feed aggregator

SummaryJoint petrophysical inversion is a powerful technique for using multiple geophysical modalities to estimate petrophysical or geotechnical parameters of the subsurface. A precise knowledge of the petrophysical laws for the full model domain is imperative to enable petrophysical coupling. In this work, we investigate the effect of partially invalid petrophysical laws on the inversion of a synthetic data set, using electrical resistivity tomography (ERT) and seismic traveltime data to image a CO2 plume in a Carbon Capture and Storage (CCS) setup. We consider a model consisting of a reservoir and a caprock in which only the reservoir can be described by a petrophysical law. We first apply a conventional (joint) petrophysical inversion (JPI) and show that the use of wrong petrophysical laws leads to systemic artefacts within the parts of the model in which the petrophysical relations are invalid. We then present a new hybrid partially petrophysically coupled joint inversion (P-JPI) approach that combines petrophysical coupling for regions with valid petrophysical laws, and structural coupling, whenever no reliable petrophysical laws are available. The P-JPI approach outperforms tomography based on the individual ERT or seismic data set, as well as joint structural inversion (JSI) based on the cross-gradient functional. The partially petrophysically coupled joint inversion thus enables petrophysical coupling and provides a unique, quantitatively interpretable saturation model for the CO2-plume. We further show that it is possible to detect zones with incorrect petrophysical relations by analysing the difference of the model updates based on the stand-alone data sets. Finally, we combine the detection of zones of incorrect petrophysical laws with the P-JPI to derive an inversion scheme that is independent of prior knowledge of the validity of petrophysical laws. Our novel methods facilitate direct estimation of the petrophysical subsurface parameters from multiple geophysical measurements if petrophysical relations are only available for parts of the model domain and provide means to quantify the spatial extent of regions where the petrophysical relations are valid.

SummaryThe rapid and accurate estimation of strong ground motion is essential for seismic hazard assessment and near-real-time disaster response. Although empirical ground motion models enable fast intensity predictions, they simplify the underlying physics and exhibit large uncertainties. Conversely, physics-based simulations — while capable of more accurately predicting ground shaking — are computationally expensive, making them impractical for large-scale hazard assessments and real-time event response. To overcome these limitations, we introduce a novel two-step machine learning framework that predicts peak ground velocity (PGV) for arbitrary double-couple sources positioned anywhere within a given medium, combining the accuracy of physics-based models with near-instantaneous inference. In the first step, an ensemble of XGBoost predictors, trained on a reciprocal Green’s function database, generates a sparsely sampled PGV map for any input source. In the second step, we refine this map into a continuous spatial prediction. By leveraging Green’s function reciprocity, our approach reduces the required number of simulations in training, lowering both computational cost and storage demands. Our framework provides spatially continuous PGV predictions and inherently accounts for complex 3D geological and topographic effects. It can deliver results within seconds while maintaining accuracy up to the highest frequency captured in the physics-based simulations. This makes PGVnet ideal for applications such as rapid earthquake disaster response, as well as large-scale probabilistic seismic hazard analyses and multi-hazard digital ecosystems. Validated in the geologically complex San Francisco Bay Area, our approach generates PGV maps consistent with physics-based simulations, offering an effective balance between computational speed and accuracy.

How do avalanches affect pylons and other sensitive infrastructure? Using detailed simulations, SLF researcher Michael Kohler has shown that the compressibility of snow initially reduces avalanche pressure, but that at high speeds this buffer suddenly fails.

Globally, toxic algal blooms are becoming more frequent and severe, fueled by a warming climate and nutrient runoff. While satellites can easily spot the green carpets once they reach the surface, the "prequels" to these outbreaks remain hidden in the deep.

Oxygen isotopes data enable researchers to look far back into the geologic past and reconstruct the climate of the past. In doing so, they consider several factors such as ocean temperature and ice volume in polar regions. A new publication by an international team from Bergen (Norway) and Bremen in Nature Geoscience concludes that the Antarctic ice sheet was less dynamic during the Oligocene epoch 34 to 23 million years ago than previously assumed.

NASA astronaut Nichole Ayers captured this image of lightning while orbiting aboard the International Space Station more than 250 miles above Milan, Italy on July 1, 2025.

The extent and speed of ice moving off the ice sheets of Greenland and Antarctica into the sea—an important dynamic for climate and sea-rise modeling—has been captured over a 10-year period by satellites from the Copernicus Sentinel-1 mission.

Alaska's glaciers are melting at an accelerating pace, losing roughly 60 billion tons of ice each year. About 4,000 kilometers to the south, in California and Nevada, records for heat and dryness are being shattered, creating favorable conditions for wildfire events.

Climate change has many culprits, from agriculture to transportation to energy production. Now, add another: the deep ocean salty blob.

Think of the destruction of Earth's rainforests and a familiar image may come to mind: fires or chainsaws tearing through enormous swaths of the Amazon, releasing masses of planet-warming carbon dioxide.

Recent reports of wells drying up in New Hampshire reflect a pattern we're increasingly seeing across New England: extended dry periods and below-normal precipitation are stressing shallow groundwater systems that many homeowners depend on.

The natural sands of beaches along the Firth of Forth are being mixed with significant amounts of human-made materials like bricks, concrete, glass and industrial waste, new research has revealed.

On clear days in Hartbeespoort, South Africa, satellite images often reveal a reservoir with shades of deep blue interrupted by drifting patches of vivid green. These shifting features indicate algae blooms, which can affect water quality, ecosystems, and nearby human communities.

The universe never fails to surprise. Take TOI-561 b, an Earth-sized exoplanet that circles its star on an orbit more than 30 times smaller than Mercury’s.

Despite being blasted by radiation to the point that its rocky surface is likely molten, TOI-561 b still seems to retain a thick atmosphere. This discovery, reported in The Astrophysical Journal Letters, shows that even highly irradiated planets—whose atmospheres should have been eroded long ago—can remain enshrouded in gas for billions of years.

Lava World

When it comes to constellations, Sextans (the Sextant) is largely unremarkable; its brightest stars can’t even be seen with the naked eye from a large city. But there’s a star in Sextans that is home to a miniature solar system: TOI-561, roughly twice as old as the Sun, has four planets orbiting it. And the innermost of those planets, known as TOI-561 b, holds the special honor of being what’s called an ultrashort-period exoplanet. That’s a world no larger than twice the radius of Earth that whips around its host star in 1 day or less.

“We do not expect that an atmosphere can survive.”

Ultrashort-period exoplanets are rare—only several dozen are known to exist—and they’re extreme: They orbit so close to their host stars that they typically have dayside temperatures above the melting point of rock, leading researchers to dub them “lava worlds.” Ultrashort-period exoplanets are also planets on a journey—it’s thought that they formed farther away from their stars and migrated inward over time.

Many ultrashort-period exoplanets observed to date also don’t have atmospheres. That makes sense, said Rafael Luque, an astrophysicist at the Institute of Astrophysics of Andalusia in Granada, Spain, not involved in the new research. These extreme worlds are literally being irradiated by their host stars, he said. “We do not expect that an atmosphere can survive.”

A Puffed-Up World?

Earlier observations revealed both the size and mass of TOI-561 b. Taken together, those data suggest an anomalously low density for the planet, roughly 4.3 grams per cubic centimeter. (Earth’s average density, for comparison, is about 5.5 grams per cubic centimeter.)

There are several explanations for that finding, said Nicole Wallack, an astronomer at Carnegie Science in Washington, D.C., and a member of the research team. For instance, TOI-561 b might lack an iron core. But a more likely scenario is that it’s a puffed-up planet that appears larger and therefore less dense than it actually is, said Wallack.

And a thick atmosphere is the most logical culprit for a puffed-up exoplanet, she explained. “It could have an atmosphere that’s making the planet appear larger in radius but isn’t influencing its mass as much.”

To test that idea, Wallack and her colleagues, led by Johanna Teske, an astronomer at Carnegie Science, recently observed TOI-561 b and its host star using the James Webb Space Telescope. The researchers collected near-infrared observations of four orbits of the planet, each of which lasted only about 11 hours.

“Atmospheres are much better than solid rocks are at transporting heat.”

For this new study, the team focused on data collected around the time of so-called secondary eclipse. That’s when a planet passes behind its star, as seen from a telescope’s perspective. By comparing observations recorded when the star and planet are both visible to those recorded when just the star is visible, it’s possible to home in on just the signal from the planet, said Wallack. For TOI-561 b, the team divided that planet signal into seven near-infrared wavelength bins and looked at how the light was distributed as a function of wavelength.

That investigation allowed the team to estimate the approximate temperature of TOI-561 b: about 1,700–2,200 K. That’s significantly cooler than the roughly 3,000 K expected on the basis of the temperature of the star and TOI-561 b’s distance from it. “The planet appears to be colder than we would have expected,” said Wallack.

An atmosphere is the best explanation for that discrepancy, Teske and her colleagues proposed. The presence of an atmosphere would allow heat to be redistributed away from a planet’s warmer dayside and toward its cooler nightside. That process of heat distribution is much more efficient than relying on rocks to do the same thing, said Wallack. “Atmospheres are much better than solid rocks are at transporting heat.”

TOI-561 b might not be a complete outlier when it comes to having an atmosphere. After all, a handful of other ultrashort-period exoplanets, such as 55 Cancri e, are believed to be enshrouded in gas.

Hunting for Molecules

After analyzing the Webb observations, the researchers modeled signals that would be expected from an atmosphere containing varying proportions of molecules such as water, carbon dioxide, and carbon monoxide. They found that their data were no more consistent with one model than another. The relatively wide spectral binning that the team adopted—just seven data points over a range of roughly 2.7–5.1 micrometers—may have precluded detecting any molecule-specific features, the team concluded.

Even though the composition of TOI-561 b’s atmosphere remains inconclusive, there’s good evidence that it exists, said Michael Zhang, an astronomer at the University of Chicago not involved in the research. “I believe that there is an atmosphere.”

And that atmosphere is most likely composed of material outgassed from TOI-561 b’s molten surface. That inference can guide logical follow-on work modeling the planet’s atmosphere, said Zhang. “You can test compositions that you expect would be outgassed from the magma ocean.”

Analyzing TOI-561 b’s nightside signal—something that’s possible with the researchers’ current dataset—will also be important, said Zhang. It’s a tough measurement to make, but because atmospheres are good at redistributing heat, he explained, even the side of TOI-561 b facing away from its star should be detectable. “The nightside should be warm.”

—Katherine Kornei (@KatherineKornei), Science Writer

Citation: Kornei, K. (2026), A “lava world” unexpectedly hosts an atmosphere, Eos, 107, https://doi.org/10.1029/2026EO260019. Published on 7 January 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.

An fascinating case study from the 24 June 2025 Granizal landslide in Medellín, Colombia, which killed 27 people and destroyed 50 homes, shows demonstrates that it is not just the urban poor that are exposed to landslides.

That urban areas can be subject to high levels of landslide risk is well-established – commonly cited examples are Hong Kong (which has a huge programme to manage the risk), Sao Paolo and Medellín, amongst other places. The well-established pattern is that it is the urban poor that have the highest levels of risk, being forced to live on slopes on the margins of the conurbation, often with poor planning and low levels of maintenance of, for example, drainage systems.

A fascinating open access paper (Ozturk et al. 2025) has just been published in the journal Landslides that suggests that this pattern might be beginning to change under the impacts of climate change. The paper examines the 24 June 2025 Granizal landslide in Medellín, Colombia, which killed 27 people and destroyed 50 houses. I wrote about this landslide at the time, including this image of the upper part of the landslide:-

The main body of the 25 June 2025 landslide at Granizal in Colombia. Still from a video posted to Youtube by Cubrinet.

The location of the headscarp of the Granizal landslide is [6.29587, -75.52722].

The analysis of Ozturk et al. (2025) shows that this is a 75,000 cubic metre failure with a source area length of 143 m and a width of 50 m. The landslide was triggered by rainfall over a 36 hour period.

The authors’ analysis suggests that the landslide occurred on terrain that is steep even by the standards of Medellín, and at a comparably high elevation for the city. They have then looked at the distribution of income tax bands for the city according to both elevation and slope angle:-

Hillslope angle (a) and elevation (b) of the built up area in Medellín, categorized by utility tax, known as Strata, which determines the socio-economic status of different neighbourhoods. For example, the utility tax decreases as the categories get lower. Hillslope angle increases generally towards poorer categories. Figure from Oztuk et al. (2025), with the caption lightly edited.

The diagram shows that in Medellín, the poorest people live on the steepest slopes, and thus (at the first order) are more at risk of landslides. People with higher income levels tend to live on areas with a lower slope angle – the more affluent you are, the lower your landslide risk. However, this pattern reverses for those in the highest tax band (i.e. the richest). Those people live on steeper slopes (although not as steep as for the poorest people).

A similar pattern emerges for elevation, although the pattern is weaker. But compare Utility tax categories 5 and 6 for example – the richest people migrate to higher elevations.

This probably represents a desire by the most affluent to live in locations with the best views and in which they can have larger plots of land. A similar pattern is seen elsewhere – for example, property prices in The Peak in Hong Kong are very high.

It has been possible to live in these higher risk locations because of good identification of hazards for those that can afford it, the use of engineering approaches to mitigate the hazard and good maintenance of drains. These options are available to those with money, who live in “formal neighbourhoods” rather than unplanned communities. Of course, as Ozturk et al. (2025) remind us, the vulnerability of these communities is still much lower than that of the poor.

But Ozturk et al. (2025) make a really important point:-

“…we should not forget that climate change is gradually intensifying and may soon render the design criteria used for planning formal neighbourhoods obsolete. Hence, our concluding message is that future rainfall changes may also lead to catastrophic landslide impacts in formally planned urban neighbourhoods, challenging the assumption that only informal settlements are at high risk.”

The vulnerability of the poorest communities means that this is where the highest risk will continue to be located, and this is where the greatest levels of loss will occur. But our rapidly changing environment means that even more affluent communities are facing increasing levels of risk.

Reference

Ozturk, U., Braun, A., Gómez-Zapata, J.C. et al. 2025. Urban poor are the most endangered by socio-natural hazards, but not exclusively: the 2025 Granizal Landslide case. Landslides. https://doi.org/10.1007/s10346-025-02680-y

Return to The Landslide Blog homepage 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.

SummaryRevil asserted in the comment that none of Macnae’s paper is novel. The paper however introduced a novel method of chargeability prediction as the fraction of pores blocked by metallic particles rather than the prediction using limiting Maxwell effective medium estimates based on volume fractions. This reply presents an analysis of two cases where the novel chargeability prediction proves to be significantly better than earlier methods when applied to laboratory pyrite-clay mixtures and to published petrophysical data from a Co-Cu disseminated mineral deposit. Another item of novelty in the paper was emphasis that the resistivity and conductivity time-constants can differ by orders of magnitude for the high chargeabilities of economic sulphide deposits, a fact not commonly recognised in the literature. Revil asserts in the comment that the term Induced Polarization (IP) should explicitly exclude dielectric effects and analogies as discussed in the paper, an assertion inconsistent with the early literature on IP and the fact that both diffusive and dielectric effects can affect low-frequency data. The reply provides detail on the physical nature of equivalent circuits, and how they can mechanistically model the IP phenomenon and the topology of conductive paths in materials, an issue that I did not emphasize in the paper as I thought it would have been obvious to most readers.

SummaryVolcanic and geothermal areas usually feature highly rugged and variable topography, with both steep and relatively flat areas. Potential field geophysical data being very sensitive to topographic changes, it can be challenging to accurately simulate data in such regions. Traditional modeling approaches for potential field data typically involve discretizing the physical space using rectangular prisms, or alternatively using slightly more sophisticated geometries such as polyhedrons. However, in both cases, these discretizations may lead to an under- or over- estimation of topographic effect on simulated data, unless a very fine discretization around observation points is used, consequently leading to an increase in the computational burden. To address this issue, we introduce new methodological strategies to simulate potential field data in regions with rugged topography. We propose the use of a numerical integration scheme over deformable hexahedral elements that conform to topographic variations, to numerically evaluate the integral equations governing gravity and magnetic anomalies. Density and magnetization properties are defined at grid nodes and interpolated within the elements using polynomial functions. The numerical integration relies on the use of a Gaussian quadrature, combined with a local refinement of the mesh designed to simultaneously increase the precision of the numerical integrals by reducing the effect of singularities and incorporating a more precise description of the topography at the vicinity of measurement points. This refinement is coupled with a discontinuous optimization of the elevation of geometrical nodes lying at the surface of the model by minimizing the distance between the interpolated topographic surface and a point cloud provided by a high-resolution Digital Elevation Model (DEM). The predictions at each observation points are computed with different refined versions of the mesh in order to minimize computational cost. Physical properties within the refined elements are extrapolated from the nodes of the original non-refined mesh in order not to introduce additional unknown physical parameters for the later implementation of this code for the inversion of the potential field data. The approach is first validated by comparing gravity and magnetic predictions with the analytical solution for a simple rectangular prism. We further test the method with realistic simulations using the complex topography of the Krafla geothermal area in northern Iceland. Simulation results are compared against the forward gravity and magnetic responses of a high-resolution benchmark model (discretized with 2 m × 2 m rectangular prisms) computed using the open-source software Tomofast-x (Ogarko et al. 2024). Finally, we use the same high-resolution model to quantify typical errors associated with coarser rectangular prism discretizations (cell sizes of 25 m, 50 m, and 100 m). We demonstrate that these errors can be comparable in magnitude to real geophysical anomalies and are not reproduced when using our proposed numerical approach.

The circumglobal teleconnection pattern (CGT) is a key mode of atmospheric variability during boreal summer, identified by an upper-tropospheric wave train propagating along the subtropical jet. CGT is one of the critical drivers of Northern Hemisphere mid-latitude heat waves. However, how the structure of CGT responds to global warming and its effect on future heat wave characteristics remains inconclusive.

Earth system box models are essential tools for reconstructing long-term climatic and environmental evolution and uncovering Earth system mechanisms. To overcome the spatiotemporal resolution limitations of current deep-time models, a research team has developed CESM-SCION, a new-generation high-resolution climate-biogeochemistry coupled model. This model advances the spatiotemporal resolution of long-term Earth system simulations to a new level and identifies marine regression as a key driver of the Late Paleozoic Ice Age onset.

Publication date: Available online 2 January 2026

Source: Advances in Space Research

Author(s): Eman Albalawi