How velocity models change earthquake shaking predictions in southwest China

Science China Press

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image: 

Simulated seismic intensity patterns for the 5 September 2022 Mw 6.6 Luding earthquake in southwest China, calculated from peak ground velocity in the 0.02–0.5 Hz frequency range. Although the same earthquake source is used, different crustal velocity models produce markedly different shaking intensities and spatial patterns, illustrating the influence of model choice on post-earthquake ground motion assessment. Colored triangles indicate observed ground motion recorded by fixed seismic stations and strong-motion instruments.

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Credit: ©Science China Press

Accurate prediction of strong ground motion is essential for post-earthquake emergency response and seismic risk mitigation, particularly in tectonically complex regions such as the Sichuan–Yunnan area of southwest China. In physics-based ground motion simulations, subsurface structure is represented by crustal velocity models ranging from simplified one-dimensional to more detailed three-dimensional descriptions, yet the extent to which model choice influences engineering-relevant shaking predictions has remained unclear.

In a new study published in Science China Earth Sciences, researchers from Southern University of Science and Technology investigated how different velocity models affect strong ground motion simulations using the 5 September 2022 Mw 6.6 Luding earthquake as a real-world example. The team employed a finite-fault rupture model derived from seismic observations and conducted numerical simulations up to 1 Hz using nine representative velocity models that differ in data sources, resolution, and construction strategy.

Rather than focusing on waveform similarity or travel-time misfits, the study evaluated model performance using peak ground velocity (PGV), a parameter widely used in earthquake engineering and damage assessment. PGV predictions were analyzed at individual stations, across regional statistical distributions, and through spatial patterns of shaking intensity to assess the practical applicability of each velocity model.

The results show that most three-dimensional velocity models can reasonably reproduce observed PGV at frequencies below 0.3 Hz, while simulation errors increase at higher frequencies. Overall, 3D velocity models outperform traditional one-dimensional models in predicting both the amplitude and spatial distribution of ground shaking. However, systematic differences persist among individual models, with some tending to overestimate shaking intensity and others to underestimate it. These discrepancies are primarily linked to differences in shallow velocity structure, modeling strategy, and whether surface topography is included.

Importantly, the researchers found that averaging PGV predictions from multiple velocity models significantly reduces systematic bias and yields results that are more consistent with observations. This multi-model approach provides a robust and practical strategy for rapid post-earthquake ground motion assessment, especially when uncertainties in subsurface structure cannot be avoided.

The study offers quantitative guidance for selecting and applying velocity models in strong ground motion simulations and highlights the value of multi-model strategies for improving the reliability of earthquake shaking predictions in complex tectonic regions.

 

See the article:

Li T, Zhang W. 2026. Assessment of the impact of different 3D crustal velocity models on strong ground motion simulations in the Sichuan-Yunnan region. Science China Earth Sciences, 69(1): 348–365, https://doi.org/10.1007/s11430-025-1743-3

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Journal

Science China Earth Sciences

DOI

10.1007/s11430-025-1743-3 

Method of Research

Computational simulation/modeling

 

University of Houston BRAIN Center finds exposure to nature associated with reductions in negative emotions

Research indicates urgent need to integrate nature into urban design to increase brain capital

University of Houston

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Renowned neuroscientist Jose Luis Contreras-Vidal, Hugh Roy and Lillie Cranz Cullen Distinguished Professor of Electrical and Computer Engineering and director, NSF IUCRC BRAIN Center, is reporting that exposure to nature can increase brain health.

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Credit: University of Houston

You probably heard it from your mom a thousand times – fresh air and sunshine; it’s the cure for most anything. Now scientists at the University of Houston concur, measuring the impact of mother’s advice on mother nature to find that exposure to nature is associated with reductions in negative emotions. 

Given that nearly 90% of the U.S. population is projected to reside in urban areas by 2050, researchers say integrating nature into urban design and public health initiatives is an increasingly recognized national public health and economic priority for improving emotional wellbeing.  

"Findings from this systematic review support the notion that nature exposure is a critical determinant of brain health and therefore brain capital. Thus, promoting and maintaining healthy environments is critical to promote and grow the world’s brain capital,” said renowned brain scientist Jose Luis Contreras-Vidal, Hugh Roy and Lillie Cranz Cullen Distinguished Professor of Electrical and Computer Engineering and director, NSF IUCRC BRAIN Center (Building Reliable Advances and Innovation in Neurotechnology). He led a team of researchers through a systematic review and meta-analysis of the impact of nature on wellness.  

The team examined the results from 2,101 participants in 33 studies combining neuroimaging and psychological assessments during exposure to real, virtual or imagined natural environments. EEG was the most widely used neuroimaging modality across the studies reviewed. 

“Healthy populations showed a more balanced psychological response, with nature exposure being associated with both increases in positive emotions and reductions in negative emotions,” reports Contreras-Vidal in the International Journal of Environmental Research and Public Health. “Growing interest in how nature influences the brain has driven research toward understanding its neurophysiological impact. This interest has recognized that genetics alone cannot account for health risk factors and that environmental exposures play a substantial role in shaping brain health.” 

The team examined brain studies that included several different tasks: 

• Imagery: The most popular task across studies, images of nature consistently demonstrated significant effects of nature on well-being. Eight studies reported increases in positive emotions while seven observed decreases in negative emotions.  

• Virtual Reality: Eight studies implemented VR-based exposure to nature, all of which used EEG as their neuroimaging modality. Six studies reported decreases in negative emotions and five reported increases in positive emotions.  

• Walking Outdoors: Five studies reported an increase in positive emotions and four reported decreases in negative emotions. 

While studies employing psychological and neuroimaging can potentially provide a shift in understanding of the neurophysiological impact of nature on brain health and wellness, there is still much to know, and Contreras-Vidal has suggestions. 

“EEG studies should expand their scope to incorporate neural metrics like functional connectivity, while prioritizing standardization of real-world multimodal data for study comparisons and effective inclusion of AI,” he said.  

“Ultimately, the goal is to design Nature prescriptions (Nature Rx) to promote brain health and treat mental illnesses across the lifespan,” said Contreras-Vidal. 

Based on the findings, the BRAIN Center is working on a study on the neural mechanisms underlying nature’s impact on brain health and wellness in Houston’s Third Ward neighborhood along the green corridor and on the UH campus’ pollinator gardens. 

 

 

 

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Journal

International Journal of Environmental Research and Public Health

Article Title

A Systematic Review and Meta-Analysis of EEG, fMRI, and fNIRS Studies on the Psychological Impact of Nature on Well-Being

Article Publication Date

17-Mar-2026

 

Overconfident CEOs are less likely to delegate responsibility – particularly when it may help the most

North Carolina State University

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A new study finds overconfident CEOs are less likely to delegate responsibilities to underlings, particularly in settings that involve complex transactions – such as hammering out the details of high-stakes deals.

“Organizations have only gotten more complex over time, often operating in multiple countries across many different sectors,” says Jared Smith, co-author of a paper on the work and a professor of finance in North Carolina State University’s Poole College of Management. “As a result, it is important for modern companies to bring more voices to the table. Involving more people who have more varied expertise and experiences can be valuable in helping companies navigate a complex business environment.

“In other words, delegation is an important tool for CEOs,” says Smith. “It can help them bring in expert voices while also freeing up their own time to tackle the multitude of issues facing any enterprise. We wanted to see whether there is a relationship between overconfidence in CEOs and their willingness to delegate – because that may have meaningful implications for their organization.”

To explore this issue, the researchers focused on 3,690 mergers and acquisitions by publicly traded companies between 2000 and 2019. The researchers looked only at transactions with a value of at least $50 million and that constituted at least 1% of the acquiring company’s equity.

Those mergers and acquisitions involved 1,634 CEOs. The researchers used an established technique to assess the confidence of those CEOs based on how the executives made use of their stock options. And to assess the extent to which those CEOs were willing to delegate responsibility, the researchers looked at press releases and news articles about the 3,690 mergers and acquisitions (M&As).

“In general, if anyone other than a C-suite executive is mentioned in these releases, it strongly suggests that the person who was mentioned played a meaningful role in the M&As,” Smith says.

The researchers also looked at “background of the merger” documents that acquiring companies submit to the Securities and Exchange Commission, which detail all relevant meetings that took place between companies while arranging the relevant transaction.

“We found that if someone other than an executive was mentioned in a press release or news article, that person was very likely involved in meetings that took place during the M&A process,” Smith says. “This helps validate the use of news releases and articles as a tool for determining whether an executive is willing to delegate responsibility.”

The researchers found that 41% of the CEOs in their data set were overconfident. And when the researchers compared the behavior of overconfident CEOs to the behavior of the overall group, they found that overconfident CEOs were 10-15% less likely than average to delegate responsibility.

The researchers also found that the relationship between overconfidence and delegation behavior varied quite a bit depending on the nature of the M&A.

“For example, when a firm was acquiring a company in an industry sector it was not previously involved in, overconfident CEOs were even less likely to delegate responsibility,” Smith says. “This is notable given that these deals involve unfamiliar industries, where outside expertise is more likely to be relevant.”

However, the most surprising result was also the most statistically powerful result.

“We found that the more segments – or business arms – the acquiring firm had, the less likely overconfident CEOs were to delegate responsibility,” says Smith. “This is remarkable, because theory suggests that the more complex the CEO’s own information environment is, the more likely they are to benefit from getting outside expertise.

“It is important for leadership to be confident in their own abilities,” says Smith. “But our study suggests that executives who are overconfident are less likely to delegate responsibility to the people on their team – and that may affect the C-suite’s ability to navigate complex business situations.

“It would be interesting to see how this may be reflected in post-merger performance – that’s an area for future research.”

The paper, “Leave it to Me: Overconfident CEOs’ Lower Propensity to Delegate Acquisition Responsibility,” is published open access in the Journal of Management Studies. The paper was co-authored by Matthew Josefy of Indiana University and Daniel Greene of Clemson University.

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Journal

Journal of Management Studies

DOI

10.1111/joms.70095 

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Leave it to Me: Overconfident CEOs’ Lower Propensity to Delegate Acquisition Responsibility

Article Publication Date

20-Mar-2026

 

A complicated future for a methane-cleansing molecule

A new model shows how levels of the “atmosphere’s detergent” may rise and fall in response to climate change.

Massachusetts Institute of Technology

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Methane is a powerful greenhouse gas that is second only to carbon dioxide in driving up global temperatures. But it doesn’t linger in the atmosphere for long thanks to molecules called hydroxyl radicals, which are known as the “atmosphere’s detergent” for their ability to break down methane. As the planet warms, however, it’s unclear how the air-cleaning agents will respond. 

MIT scientists are now shedding some light on this. The team has developed a new model to study different processes that control how levels of hydroxyl radical will shift with warming temperatures. 

They find that the picture is complicated. As temperatures increase, so too will water vapor in the atmosphere, which will in turn boost the molecule’s concentrations. But rising temperatures will also increase “biogenic volatile organic compound emissions” — gases that are naturally released by some plants and trees. These natural emissions can reduce hydroxyl radical and dampen water vapor’s boosting effect. 

Specifically, the team finds that if the planet’s average temperatures rise by 2 degrees Celsius, the accompanying rise in water vapor will increase hydroxyl radical levels by about 9 percent. But the corresponding increase in biogenic emissions would in turn bring down hydroxyl radical levels by 6 percent. The final accounting could mean a small boost, of about 3 percent, in the atmosphere’s ability to break down methane and other chemical compounds as the planet warms. 

“Hydroxyl radicals are important in determining the lifetime of methane and other reactive greenhouse gases, as well as gases that affect public health, including ozone and certain other air pollutants,” says study author Qindan Zhu, who led the work as a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). 

“There’s a whole range of environmental reasons why we want to understand what’s going on with this molecule,” adds Arlene Fiore, the Peter H. Stone and Paola Malanotte Stone Professor in EAPS. “We want to make sure it’s around to chemically remove all these gases and pollutants.”

Fiore and Zhu’s new study appears today in the Journal of Advances in Modeling Earth Systems (JAMES). The study’s MIT co-authors include Jian Guan and Paolo Giani, along with Robert Pincus, Nicole Neumann, George Milly, and Clare Singer of Lamont-Doherty Earth Observatory and the Columbia Climate School, and Brian Medeiros at the National Center for Atmospheric Research. 

A natural neutralizer

The hydroxyl radical, known chemically as OH, is made up of one oxygen atom and one hydrogen atom, along with an unpaired electron. This configuration makes the molecule extremely reactive. Like a chemical vacuum cleaner, OH easily pulls an electron or hydrogen atom away from other molecules, breaking them down into weaker, more water-soluble forms. In this way, OH reduces a vast range of chemicals, including some air pollutants, pathogens, and ozone. And changes in OH are a powerful lever on methane. 

“For methane, the reaction with OH is considered the most important loss pathway,” Zhu says. “About 90 percent of the methane that’s removed from the atmosphere is due to the reaction with OH.”

Indeed, it’s thanks to reactions with hydroxyl radical that methane can only stick around in the atmosphere for about a decade — far shorter than carbon dioxide, which can linger for 1,000 years or longer. But even as OH breaks down methane already in the atmosphere, more methane continues to accumulate. Rising methane concentrations, in addition to human-derived emissions of carbon dioxide, are driving global warming, and it’s unclear how OH’s methane-clearing power will keep up. 

“The questions we’re exploring here are: What are the main processes that control OH concentrations? And how will OH respond to climate change?” Fiore says. 

An aquaplanet’s air

For their study, the researchers developed a new model to simulate levels of OH in the atmosphere under a current global climate scenario, compared to a future warmer climate. Their model, dubbed “AquaChem,” is an expansion of a simplified model that is part of a suite of tools developed by the Community Earth System Model (CESM) project. The model that the team chose to build off is one that represents the Earth as a simplified “aquaplanet,” with an entirely ocean-covered surface. 

Aquaplanet models allow scientists to study detailed interactions in the atmosphere in response to changes in surface temperatures, without having to also spend computing time and energy on simulating complex dynamics between the land, water, and polar ice caps. 

To the aquaplanet model, Zhu added an atmospheric chemistry component that simulates detailed chemical reactions in the atmosphere consistent with the applied surface temperatures. The chemical reactions that she modeled represent those that are known to affect OH concentrations. 

OH is primarily produced when ozone interacts with sunlight in the presence of water vapor. For instance, scientists have found that OH levels can vary depending certain anthropogenic and natural emissions, all of which Zhu incorporated separately and together into the AquaChem model in order to isolate the impact of each process on OH.

The emissions in particular include carbon monoxide, methane, nitrogen oxides, and volatile organic compounds (VOCs), some of which are emitted through human practices, and others that are given off by natural processes. One type of naturally-derived VOCs are “biogenic” emissions — gases, such as isoprene, that some plants and trees emit through tiny pores called stomata during transpiration. 

Into the AquaChem model, Zhu plugged in data that were available for each type of emissions from the year 2000 — a year that is generally considered to represent the current climate in a simplified form. She set the aquaplanet’s sea surface temperatures to the zonal annual mean of that year, and found that the model accurately reproduced the major sensitivities of OH chemistry to the underlying chemical processing as simulated in a more complex chemistry-climate model. 

Then, Zhu ran the model under a second, globally warming scenario. She set the planet’s sea surface temperatures to warm by 2 degrees Celsius (a warming that is likely to occur unless global anthropogenic carbon emissions are mitigated). The team looked at how this warming would affect the various types of emissions and chemical processes, and how these changes would ultimately affect levels of OH in the atmosphere. 

In the end, they found the two biggest drivers of OH levels were rising water vapor and biogenic emissions. They found that global warming would increase the amount of water vapor to the atmosphere, which in turn would boost production of OH by 9 percent. However, this same degree of warming would also increase biogenic emissions such as isoprene, which reacts with and breaks down OH, bringing down its levels by 6 percent. 

The team recognizes that there are many other factors that affect the response of isoprene emissions to surface warming. Rising CO2, not considered in this study, may dampen this temperature-driven response. Of all the factors that can shift OH levels under global warming, the researchers caution that biogenic emissions are the most uncertain, even though they appear to have a large influence. Going forward, the scientists plan to update AquaChem to continue studying how biogenic emissions, as well as other processes and climate scenarios, could sway OH concentrations. 

“We know that changes in atmospheric OH, even of a few percent, can actually matter for interpreting how methane might accumulate in the atmosphere,” Zhu says. “Understanding future trends of OH will allow us to determine future trends of methane.”

This work was supported, in part, by Spark Climate Solutions and the National Oceanic and Atmospheric Administration. 

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Written by Jennifer Chu, MIT News

Paper: “Uncertain natural emissions dampen the increase in tropospheric hydroxyl radical (OH) with idealized surface warming”

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025MS005248

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Journal

Journal of Advances in Modeling Earth Systems

DOI

10.1029/2025MS005248 

Article Title

“Uncertain natural emissions dampen the increase in tropospheric hydroxyl radical (OH) with idealized surface warming”