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SummaryWe present a novel method for generating kinematic rupture models for near-source broadband ground motion simulations. Our approach constructs realistic rupture-parameter distributions for slip, rupture velocity and rise time using Von Karman (VK) fields. To more realistically model the slip pattern, we propose rescaling the VK field to follow a truncated exponential distribution rather than a Gaussian, following previous findings on inversion results. For rupture propagation, we initiate the rupture from slip-constrained hypocenter locations, which is crucial for accurately capturing directivity effects. Finally, to characterize the local slip-rate evolution at each computational point on the fault, we propose to employ the regularized Yoffe functions to which small-scale variations are added using 1D VK-fields whose properties are constrained from a database of dynamic rupture simulations. The statistical properties of these fields are calibrated using a database of dynamic rupture simulations, ensuring appropriate high frequency radiation from the generated rupture.Our rupture generator produces kinematic source descriptions to simulate ground motions that successfully reproduce the mean and standard deviation from ground motion models (GMM) for Mw 6.0-7.0 earthquakes. Additionally, our generator allows for the integration of low-frequency source inversions and complements the high frequency radiation of a seismic rupture with physics-constrained stochastic variations. Our broadband pseudo-dynamic kinematic rupture generator facilitates and possibly improves the simulation of realistic high-frequency ground motions to advance seismic hazard analysis.

Salt intrusion is a growing concern worldwide. Eleonora Saccon, who completed a master's degree in climate change ecology in her native Italy, studied the effects of salty surface water at the NIOZ branch in Zeeland.

UC Riverside researchers have discovered a piece that was missing in previous descriptions of the way Earth recycles its carbon. As a result, they believe that global warming can overcorrect into an ice age.

A vital waterway connecting the Atlantic and Pacific oceans, the Panama Canal relies on fresh water supplied by a reservoir to raise and lower the locks that allow the transit of thousands of ships a year.

Typhoons and their Atlantic counterparts—hurricanes—can develop into massively destructive storms that can take a severe toll on both infrastructure and human life. Climate change is additionally spurring even more intense storms with higher wind speeds and rainfall.

Earth scientists often face huge challenges when researching Earth's history: many significant events occurred such a long time ago that there is little direct evidence available. Consequently, researchers often have to rely on indirect clues or on computer models.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Journal of Geophysical Research: Solid Earth

Seismologists have long detected unusual structures deep beneath continents at mid-lithospheric depths (80–120 kilometers), but their cause has remained uncertain.

In a new study, Zhang et al. [2025] use state-of-the-art computer simulations that combine first-principles (or fundamental assumption) calculations with machine learning to discover a new form of calcium carbonate, an important carbon-bearing mineral in Earth’s deep interior. This newly identified phase undergoes remarkable elastic softening under mid-lithospheric conditions, greatly reducing seismic wave speeds. Even trace amounts of such carbonate could explain the puzzling seismic signals and anomalous electrical properties observed beneath ancient continental regions.

These findings suggest that carbonates play a far more important role in shaping continental structure than previously recognized. Moreover, the results demonstrate that advanced computational methods can uncover unexpected aspects of the deep carbon cycle and the long-term stability of continental roots.

Citation: Zhang, P., Man, L., Yuan, L., Wu, X., & Zhang, J. (2025). Ultra-low-velocity disordered CaCO3 may explain mid-lithospheric discontinuities. Journal of Geophysical Research: Solid Earth, 130, e2025JB031906. https://doi.org/10.1029/2025JB031906

—Jun Tsuchiya, Editor, 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.

SummarySeismic scattering waves in random media are usually regarded as noise in conventional seismic imaging, inversion and interpretation. However, the spatial and temporal variation of the scattering energy depends on the stochastic properties of the random media. The extraction of heterogeneity information such as the correlation scale and fluctuation strength from seismic scattering waves remains a challenge. These parameters are inverted from real scattering data by fitting the synthetic envelopes to the observed seismic envelopes. The synthetic envelopes are usually computed using the Monte-Carlo radiative transfer (MCRT) method. However, physical verification of the stochastic parameter inversion based on MCRT theory has not been realized although it is believed to be correct. To this end, we conducted a physical modelling experiment using an ultrasonic acquisition system and recorded the transmitted wavefields through an artificial heterogeneous medium. In this paper, the elastic MCRT method was used to simulate the energy transport, and the correlation length and fluctuation strength of the artificial heterogeneous medium were inverted with a revised objective function, which can better balance the energy level of direct waves and scattering waves in the inversion process. The inversion results of the correlation scale and fluctuation strength match well with true values, suggesting that this method is accurate and reliable. A combination of our physical experiments and the MCRT theory gives strong proof that this inversion method is correct. Therefore, it can be used with confidence to estimate the properties of the heterogeneities from the ‘undesired’ scattering waves, both in the oil/gas exploration and earth structure investigation.

SummaryThe attenuation operator t* represents the total path attenuation and characterizes the amplitude decay of a propagating seismic wave. Calculating t* is typically required in seismic attenuation tomography. Traditional methods for calculating t* require determining the ray path explicitly. However, ray tracing can be computationally intensive when processing large datasets, and conventional ray tracing techniques may fail even in mildly heterogeneous media. In this study, we propose a modified fast sweeping method (MFSM) to solve the governing equation for t* without explicitly calculating the ray path. The approach consists of two main steps. First, the traveltime field is calculated by numerically solving the eikonal equation using the fast sweeping method. Second, t* is computed by solving its governing equation with the MFSM, based on the discretization of the gradient of t* using an upwinding scheme derived from the traveltime gradient. The MFSM is rigorously validated through comparisons with analytical solutions and by examining t* errors under grid refinement in both simple and complex models. Key performance metrics, including convergence, number of iterations, and computation time, are evaluated. Two versions of the MFSM are developed for both Cartesian and spherical coordinate systems. We demonstrate the practical applicability of the developed MFSM in calculating t* in North Island, and discuss the method’s efficiency in estimating earthquake response spectra.

SummaryVarious methods for determining the magnetic field at the core-mantle boundary (CMB) from the observed geomagnetic core field have been explored over recent decades. These include the harmonic downward continuation of surface data and the stabilised iterative upward continuation. The instability of the inverted poloidal magnetic field at the CMB for a radial conductivity structure is complemented by the non-uniqueness of determining the toroidal magnetic field at the CMB for a laterally inhomogeneous conductivity model. We reformulate this unstable and non-unique inverse problem as an iterative upward continuation approach, in which the magnetic field at the CMB is successively updated. The uniqueness of the inverse solution is ensured by the initial choice of the toroidal magnetic field at the CMB, while the stability is achieved by stopping the iterations once the desired tolerance is reached between the spectral index of the updated solution and that obtained from numerical geodynamo simulations. We consider two significantly different radial electrical conductivity models of the lower mantle, each with conductance near 108 S: conductivity model A, based on external electromagnetic sounding, which includes a significant conductivity increase in a 10 km thick layer above the CMB, and conductivity model B, characterized by a gradual conductivity increase determined from the Voigt-Reuss-Hill average of the bridgmanite-ferropericlase aggregate, with an additional conductivity increase in the 300 km thick D” layer associated with post-perovskite. Models A and B bracket the lower and upper bounds of conductivity structures derived from thermal and compositional constraints below 1600 km depth. We find that the differences between the magnetic field components at the CMB inverted for models A and B are approximately 1-2 per cent of the total field. To explore lateral variations, we construct a synthetic model of the Pacific and African superplumes by simplifying their geometric shapes, estimating the temperature increase within the plumes and allowing mantle mineral activation energies to vary only with temperature. Our results show that, in the regions of the superplumes, the poloidal and toroidal magnetic fields at the CMB change by approximately 12,000 nT and 2,500 nT, respectively. The changes in the horizontal poloidal field at the CMB are comparable in magnitude to those resulting from substituting model A with model B. However, the changes in the radial field inverted for the three-dimensional plume conductivity model are significantly larger than those arising from replacing model A with model B.

The highest rock wall in the Alps—the Monte Rosa East Face on the border between Italy and Switzerland—has for the first time been surveyed three-dimensionally with high precision. An international research team from the universities of Milan, Prague and Heidelberg has taken more than 3,000 high-resolution photos from a helicopter. Using a special method, a detailed 3D model is now emerging.

Tornadoes on the outer edges of a typhoon's spiral rain bands are a severe convective weather phenomenon that occurs on the periphery of tropical cyclone systems. Compared to the core region near the typhoon's center, the atmospheric instability and vertical wind shear conditions in these outer areas often combine in more subtle and easily overlooked ways, making their occurrence and development more sudden and localized. This poses greater challenges for forecasting and early warning.

body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news that impacts science and scientists today.

Unchecked greenhouse gas emissions could cause the world’s income to fall by nearly a quarter within the century, projects a new study published in PLOS Climate.

“Climate change reduces income in all countries, hot and cold, rich and poor alike.”

“Climate change reduces income in all countries, hot and cold, rich and poor alike,” the study’s authors wrote in a press release.

Gross domestic product, or GDP, is the total value of goods and services produced in a given year. A country’s per-capita GDP is a measure of the average income of a person living there. 

In the new study, researchers turned to information about the previously studied link between rising temperatures and GDP, along with possible scenarios of future warming, called Shared Socioeconomic Pathways. They used this data to simulate more precisely how rising temperatures might impact global GDP over time.

Their projections show warming could cause widespread economic losses as higher temperatures and climate variability impact the activities of industries including agriculture and manufacturing. But reducing greenhouse gas emissions could soften the effect, the authors write. 

In a moderate emissions scenario (SSP2-4.5), global GDP decreased by about 2.5% by 2100. In a high-emissions scenario with minimal adaptation (SSP3-7.0), the projections showed global per-capita GDP dropping by up to 11%. And in a more extreme emissions scenario (SSP5-8.5) without any climate mitigation or adaptation, the researchers projected per-capita income losses of up to 24%.

Under this extreme scenario, the United States would lose nearly a third of its per-capita GDP by 2100. 

The estimated changes in global income compared to the 1960-2014 warming trend, as well as a world without climate change, varied depending on the warming scenario that the researchers used. Credit: Mohaddes and Raissi, 2025, https://doi.org/10.1371/journal.pclm. 0000621

The results are in line with previous research from 2024, which indicated a likely decrease in global income by 11% to 29%, depending on future emissions scenarios. However, the new study finds that if the world’s governments abide by Paris Agreement goals—that is, limiting temperature increases to 0.01°C (0.02°F) per year—global GDP could slightly increase by 0.25% by 2100.

 
Related

•  Read the paper: “Rising temperatures, melting incomes: Country-specific macroeconomic effects of climate scenarios”
•  Climate Change Is Likely to Slash Global Income
• Get Involved: AGU Science Policy Action Center
 

In both the new study and previous research, low-income and hotter countries fared the worst: In the new study’s projections, countries located in hot climates and classified as low-income faced income losses between 30% and 60% of the global average. 

The publication comes on the heels of a speech at the United Nations General Assembly in which President Trump called climate change the “greatest con job ever perpetrated on the world.” That denialism won’t preserve global income, according to the authors: “Urgent action is needed to address climate change and protect economies from further income losses,” they wrote.

—Grace van Deelen (@gvd.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 © 2025. AGU. CC BY-NC-ND 3.0
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A joint research group has identified that the spatial scale of "heterogeneity" in the upper mantle, caused by a large-scale flow called a mantle plume rising from deep Earth, is less than 10 kilometers.

Most Californians are familiar with earthquakes. But researchers say the state faces an overlooked threat: "supershear" earthquakes that move so fast they outrun their own seismic waves.

Tens of thousands of earthquakes shook the Greek island of Santorini and the surrounding area at the beginning of the year. Now, researchers have published a comprehensive geological analysis of the seismic crisis in the journal Nature.

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

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

在中国，通过大规模耕作实现农业现代化的努力，将许多参与了全国大部分粮食生产的小农户推到了边缘。一个颇具前景的解决方案是“循环农业”，它通过鼓励大规模和小规模农业经营之间的合作，重点关注可持续性、生产力和农村经济发展。

在Community Science期刊关于可持续农业跨学科合作的特刊中，Li 和 Nielsen[2025]研究了中国西南部一个将柚子种植与养猪相结合的循环农业项目。作者对小农户、政府官员、金融机构员工以及其他各类利益相关者进行了35次访谈，了解了该模式面临的各种利益和风险。

他们的研究结果表明，地方政府在搭建合作平台方面发挥着关键作用，而农业合作社则是商务管理的核心。该研究还揭示了政府参与往往出于政治动机，小农户在决策过程中可能失去自主权和公平代表权等挑战。作者建议，要使循环农业真正惠及每个人，小农户需要有话语权和权力来决定自己的未来，而不能让自己的利益受到侵犯。

Citation: Li, H., & Nielsen, J. Ø. (2025). Smallholders, capital, and circular agriculture—The case of combined pomelo and pig farming in southwest China. Community Science, 4, e2025CSJ000127. https://doi.org/10.1029/2025CSJ000127

—Claire Beveridge, 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.

Human settlements around the world are moving inland and relocating away from coastlines as sea levels rise and coastal hazards grow more severe, but a new international study shows the poorest regions are being forced to stay put or even move closer to danger.

The Ganges River is in crisis. This lifeline for around 600 million people in India and neighboring countries is experiencing its worst drying period in 1,300 years. Using a combination of historical data, paleoclimate records and hydrological models, researchers from IIT Gandhinagar and the University of Arizona discovered that human activity is the main cause. They also found that the current drying is more severe than any recorded drought in the river's history.

A stalagmite in a Yucatán cave has provided new insight into the role drought may have played in Maya sociopolitical shifts more than 1,000 years ago. A recent analysis of a rainfall proxy in the Maya lowlands revealed that several episodes of severe, prolonged drought occurred during the Maya Terminal Classic Period (roughly 800–1000 CE), a time when large urban centers experienced major sociopolitical shifts.

The researchers suggest that just as climate change acts as a threat multiplier today, drought may have amplified existing troubles in Maya political centers like Chichén Itzá and Uxmal and added climate stress to societies already under pressure.

“These climate events would have affected each individual site in a very specific way depending on the resilience of that site at that time,” said lead researcher Daniel James, who studies paleoenvironmental reconstruction at University College London. “Hopefully the precision of this record allows that [analysis] to be done at individual sites…then we can really start to build up a picture of what I am certain will be a wide variety of societal responses to climate change across this time and across the region.”

Extended Droughts During Wet Seasons

During the Maya Terminal Classic Period, several Maya city-states in the southern lowlands (in modern-day Mexico, Belize, and Guatemala) experienced sociopolitical upheaval, site abandonment, and depopulation. Political and cultural centers shifted northward. Although the societal changes are clear in the archaeological record, there is still widespread debate about the potential drivers of these shifts as well as why some city-states survived while others did not.

This map of the Maya lowlands in Yucatán marks sites of prior paleoclimate studies with white squares, with this study’s site, Grutas Tzabnah, marked with an X. White circles denote Northern Maya Lowland sites, and stars denote sites of interest to this study. The land is shaded on the basis of its elevation in meters above sea level (m asl). Blue contours outline modeled mean annual total rainfalls from 1979 to 2022 in millimeters per year. Credit: James et al., 2025, https://doi.org/10.1126/sciadv.adw7661, CC BY 4.0

Drought comes up often in these debates as a potential destabilizer: Insufficient or unpredictable rainfall can lead to food instabilities, trade disruptions, disease, and even military conflicts. But previous paleoclimate studies failed to precisely pin down the timings and durations of droughts in the Maya lowlands during the Terminal Classic Period, James said.

James and his colleagues trekked to a cave called Grutas Tzabnah, in the state of Yucatán, Mexico, located near several large Classic Maya sites, including Chichén Itzá and Uxmal. This cave has been sought out before for paleoclimate studies of the region because of its accessibility and well-preserved cave formations. What’s more, Grutas Tzabnah is also a relatively shallow cave, which means that water does not take long to drip into the cave from ground level.

The researchers chose a stalagmite that has been growing for thousands of years and shows distinct annual growth layers. This particular stalagmite grew fast in the layers that dated back to the Maya Terminal Classic Period, James said, so the team was able to collect 10–20 data points within each annual layer to determine subannual, seasonal rainfall.

Researchers Daniel James (left), Ola Kwiecien (center), and David Hodell (right) install a drip water autosampler in Grutas Tzabnah to analyze seasonal changes in drip chemistry. Credit: Sebastian Breitenbach, 2022

“You can see wet seasons and dry seasons in our record, whereas previous records from the same cave are looking at annual average rainfall,” James said. “Wet season rainfall is what determines the success or failure of agriculture, as opposed to annual average.”

They measured the ages of the layers using uranium-thorium radiometric dating and rainfall quantity using a stable oxygen isotope ratio, δ18O, within calcite. Stalagmite samples that recorded a lower δ18O indicate more rainfall, while higher δ18O indicates less rainfall. The team calibrated their paleoclimate calculations with modern rainwater and cave drip measurements over a few years to ensure that they could convert the stalagmite’s δ18O measurements to rainfall.

From 871 to 1021, the stalagmite recorded eight extreme droughts during wet seasons, each lasting at least 3 years. A 4-year drought that started in 894 was interrupted by a single wet year and was followed by another 5 years of wet-season drought. A few decades later, the region had experienced 13 consecutive years of wet-season drought (929–942), longer than any multiyear drought in local historical records. This research was published in Science Advances in August.

“The chronology makes this one of the most detailed paleoclimate records available for understanding human-climate interactions during the Maya collapse period.”

“This new study represents a significant advancement in our understanding of Terminal Classic drought patterns, primarily due to its exceptional temporal resolution and robust age control with uncertainties of just a few years,” said Sophie Warken, who studies speleothems and climate variability at Universität Heidelberg in Germany and was not involved with this research.

“This high-resolution approach enables the authors to examine the timing and duration of individual drought episodes very precisely, which previous studies could only identify as broad periods of drying,” Warken added. “The chronology makes this one of the most detailed paleoclimate records available for understanding human-climate interactions during the Maya collapse period.”

One Piece of the Puzzle

While this rainfall record is a big step forward, Warken said that she would like to see it verified using additional proxies like trace elements, as well as a longer modern calibration period. She would also like to see this record extended to before and after the Terminal Classic Period to gauge whether those droughts were truly exceptional for the region.

“Such expanded paleoclimate networks could also provide crucial baselines for assessing recent and future climate changes in this vulnerable region,” she added.

Despite the fact that the extended droughts coincide with major societal shifts, James cautioned that this does not mean that drought caused these changes or were even the most important factor.

“I would love for this data to be used to pick apart individual stories from individual sites of resilience and survival, as well as the stories of disintegration of systems and abandonment and loss of population.”

“Other hardships like famine, disease, and internal violence could have been caused by drought or indeed could have been ongoing beforehand and made the society more susceptible to and less prepared for climate hardship,” James said.

Importantly, archaeological evidence suggests that two Maya cities near this cave, Chichén Itzá and the regional capital of Uxmal, did not decline at the same rate. (Uxmal declined much more rapidly.) Understanding the pressures that the two cities experienced, including drought, will be key to creating a holistic picture of how the cities functioned during the Terminal Classic Period.

“While climate stress likely played an important role in the Terminal Classic transformations,” Warken said, “the Maya’s response to drought was probably mediated by existing social, political, and economic vulnerabilities that varied between different centers and regions.”

“It could be how well were they ruled, how rigid or flexible was their political system, how good was their water management at the time,” James said.

“I would love for this data to be used to pick apart individual stories from individual sites of resilience and survival, as well as the stories of disintegration of systems and abandonment and loss of population,” he added.

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

Citation: Cartier, K. M. S. (2025), Major droughts coincided with Classic Maya collapse, Eos, 106, https://doi.org/10.1029/2025EO250361. Published on 24 September 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.