Researchers discover mechanism that can ramp up magnitude of certain earthquakes

University of Texas at Austin

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A team from The University of Texas at Austin and the University of Chile servicing a UTIG seismometer near Calama, Northern Chile, in 2024. UT graduate student Sabrina Reichert is in the background. U of Chile, Santiago researcher Bertrand J. M. Potin is in the foreground.

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Credit: Thorsten Becker/UT Austin

In July 2024, a 7.4-magnitude earthquake struck Calama, Chile, damaging buildings and causing power outages.

The country has endured violent earthquakes, including the most powerful recorded in history: a 9.5-magnitude “megathrust” event that struck central Chile in 1960, causing a tsunami and killing between 1,000 to 6,000 people. However, the Calama quake was different from the megathrust quakes that are usually associated with the most destructive events in Chile and around the world.

Megathrust earthquakes occur at relatively shallow depths. But the Calama quake occurred much deeper underground, at 125 kilometers beneath the Earth’s surface and within the tectonic slab itself.

Earthquakes this deep usually produce much more subdued shaking on the surface. But in the case of Calama, a sequence of events, discovered by researchers at The University of Texas at Austin, helped supercharge its strength. In a recent study in Nature Communications the researchers describe a newly-discovered chain of events that was responsible for increasing the earthquake’s intensity.

In addition to helping explain the tectonic forces behind the powerful quake, the findings have implications for future earthquake hazard assessments.

“These Chilean events are causing more shaking than is normally expected from intermediate-depth earthquakes, and can be quite destructive,” said the study’s lead author Zhe Jia, a research assistant professor at the UT Jackson School of Geosciences. “Our goal is to learn more about how these earthquakes occur, so our research could support emergency response and long-term planning.”

Intermediate-depth earthquakes, such as the one in Calama, were long thought to occur due to pressure building up as the rock dried out – a phenomenon called “dehydration embrittlement.” This process happens when a subducting tectonic plate dives toward the Earth’s hot interior, and the increased heat and pressure forces water out of the minerals within the rock. The dehydrated rocks are weakened and fractured, which can lead them to rupture – triggering an earthquake in the slab.

This dehydration process is typically thought to stop where temperatures exceed 650 degrees Celsius. But according to the researchers, the Calama quake was so powerful because it breached this limit – going 50 kilometers deeper into hotter zones through a second mechanism called “thermal runway.” This involves immense friction from the initial slip generating a large amount of heat at the tip of the rupture, which helps weaken material around it and propels the rupture forward.

“It’s the first time we saw an intermediate-depth earthquake break assumptions, rupturing from a cold zone into a really hot one, and traveling at much faster speeds,” said Jia, who is part of the University of Texas Institute for Geophysics (UTIG), a research unit of the Jackson School. “That indicates the mechanism changed from dehydration embrittlement to thermal runaway.”

To determine how the earthquake deformed and the extent of the rupture, the University of Texas team collaborated with researchers in Chile and the United States to integrate multiple types of analyses. This included analyzing seismic data from Chile that captured the rupture’s propagation and speed, geopositioning data from the Global Navigation Satellite System to measure how the fault slipped, and computer simulations to estimate the temperature and composition where the earthquake ruptured.

“The fact that another large earthquake is overdue in Chile has motivated earthquake research and the deployment of multiple seismometers and geodetic stations to monitor earthquakes and how the crust is deforming in the region,” said Thorsten Becker, a co-author of the study and a professor at the Jackson School’s Department of Earth and Planetary Sciences and a senior research scientist at UTIG.

Becker and Jia said that learning more about how earthquakes occur at different depths could help with understanding what controls the size and nature of likely future events, which could help predict the degree of shaking and inform infrastructure planning, early warning systems, and rapid response systems.

The research was funded by the National Science Foundation, Agencia Nacional de Investigación y Desarrollo (ANID), Chile, UC Open Seed Fund, Fundamental Research Funds for the Central Universities, and the University of Texas Institute for Geophysics.

A figure from the study illustrating the two rupture mechanisms described in the paper, dehydration embrittlement and thermal runway, and how they may have increased the force of the Calama earthquake.

Credit

Jia et al

Journal

Nature Communications

DOI

10.1038/s41467-025-63480-5 

Article Title

Deep intra-slab rupture and mechanism transition of the 2024 Mw 7.4 Calama earthquake

 

Indoor wood burners linked to a decline in lung function

European Respiratory Society

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Dr Laura Horsfall

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Credit: Laura Horsfall/ERS

Using a wood burning stove at home can lead to a decline in lung function, according to research presented at the European Respiratory Society Congress in Amsterdam, the Netherlands [1].

The study was presented by Dr Laura Horsfall, Principal Research Fellow from the Institute of Health Informatics, University College London, UK.

The use of solid fuel for domestic heating has increased in Europe due to the marketing of wood as renewable energy and high fossil fuel prices. In the UK, the proportion of harmful PM2.5 air pollution (fine particulate matter) caused by domestic solid fuel is now 20% of the total, compared with 4% for road vehicle exhaust emissions. Annual emissions, specifically from domestic wood burning, almost doubled from 3,200 tonnes in 2009 to 6,000 tonnes in 2023.

Dr Horsfall told the Congress: “We know wood burning at home emits harmful air pollution both indoors and outdoors including known carcinogens. Despite this, air pollution from this source has approximately doubled in the UK since 2009 as more people install and use wood stoves. However, the link with health outcomes in high-income countries is not well understood and residential areas with high emissions are hard to identify using existing air quality monitoring networks.

Building on a previous study that mapped the use of solid fuel burning stoves across the UK, the researchers used data from the English Longitudinal Study of Aging (ELSA) [2] to study the connection between self-reported solid fuel use at home in England and lung function decline.

They assessed patients’ lung function according to a measure called FEV1, which quantifies the amount of air a person can forcefully exhale in the first second of a breath. Lower FEV₁ values are associated with increased risk of respiratory complications and poorer health outcomes, making FEV₁ a key objective marker in monitoring diseases like COPD and asthma.

Studying health impacts is challenging because wood-burning households tend to be wealthier and healthier overall. Dr Horsfall explained: “We found that people using solid fuel had lower rates of smoking and lung disease, which can mask the true effects of solid fuel exposure.

“However, using repeated lung function measurements over an eight-year period, we found that lung function declined faster among solid fuel users compared to non-users, even after adjusting for socioeconomic and housing factors. This suggests an important link between solid fuel use and respiratory decline, despite the healthier baseline of the exposed group.

“Our study suggests that high levels of particulate matter from stoves damage respiratory tissues, causing inflammation in a similar way to cigarette smoke,” she added.

Dr Horsfall and her team now plan to investigate whether people living in or near areas with a high concentration of wood stoves, such as the wealthier parts of London, also show increased rates of respiratory issues, such as inhaler prescriptions and hospital visits for lung conditions.

Professor Ane Johannessen, Head of the European Respiratory Society’s expert group on epidemiology and environment, based at the University of Bergen, Norway, who was not involved in the research said: "In Europe, we are seeing a growing trend for using wood-burning stoves at home. Research in other parts of the world, where traditional wood burning is used in the home, has shown that this is harmful and causes asthma, COPD and lung cancer.

"These findings suggest that wood-burners used in European homes may have similar effects and should be considered a potential environmental risk factor when assessing respiratory health, especially in patients with unexplained lung function decline or chronic respiratory symptoms. Although new eco-design European wood-burners are generally considered cleaner and safer than more traditional wood stoves, many European homes still employ older wood-burners, and even the newer stoves may not be entirely risk-free.

“This study underscores the need for clearer public health guidance and regulation around domestic wood burning. People should be aware that these stoves could be harming them and their families, and doctors should be asking their patients about whether they are using stoves at home.”

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Method of Research

Observational study

Subject of Research

People

Estimated prevalence and concentration of wood fuel heat sources by Lower Super Output Area (LSOA), England and Wales. A. Top: Estimated prevalence of wood burners by LSOA, England and Wales. Bottom: Estimated prevalence of wood burners by LSOA, London. Local authorities of Richmond upon Thames, Kingston upon Thames, and Bromley highlighted in blue. B. Top: Estimated concentration of wood burners per km2 by LSOA, England and Wales. Bottom: Estimated concentration of wood burners per km2 by LSOA, London.

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Laura Horsfall/ERS

Children lose 8.45 million days of healthy life due to second hand smoke

Children from low socio-economic regions face the biggest impact

CIGARETTE DUMPING BY BIG TOBACCO

European Respiratory Society

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Dr Siyu Dai

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Credit: Siyu Dai/ERS

Children lose 8.45 million days of healthy life each year globally due to second hand smoke, according to research presented at the European Respiratory Society Congress in Amsterdam, the Netherlands [1]. Children from low socio-economic regions face the biggest impact of breathing second hand smoke, also known as passive smoking.

The study was presented by Dr Siyu Dai, Assistant Professor in the School of Clinical Medicine at Hangzhou Normal University and an Honorary Research Associate in the Department of Paediatrics at The Chinese University of Hong Kong.

She told the Congress: “Second-hand smoke is a major contributor to preventable illness and death in children and there is no safe exposure level. It is linked to chest infections, cardiovascular disease, and neurodevelopmental problems and makes asthma symptoms worse. Young children are especially susceptible because their bodies and lungs are still developing and they have little control over their own environments.

“Data from the World Health Organization estimate that second-hand smoke exposure causes 1.2 million premature deaths annually, including approximately 65,000 among children under the age of 15. But we know that many more children will suffer illness caused by other people smoking around them, so we wanted to quantify this problem globally and regionally, to provide evidence for more precise tobacco control policies.”

In the first global study to examine the impact of second-hand smoke (SHS) on children under 14 years old, Dr Dai and her colleague Miss Ruiying Jin analysed data from the Global Burden of Disease Study [2], a large international project that tracks deaths and illness from major diseases, injuries, and risk factors across the world.

One of its key measures is the disability-adjusted life year (DALY), which represents the total burden of disease. In simple terms, one DALY equals one year of healthy life lost (whether from dying too early or living with illness or disability).

Looking at data across more than 200 countries and territories, Dr Dai estimated the years lost to second-hand smoke across major disease categories from 1990 to 2021 in children aged 0–14 years. She then compared this to the Socio-demographic Index, which combines information on the economy, education, and fertility rate of countries around the world, as a representation of social and economic development.

She found that in 2021, SHS exposure contributed to 3.79 million DALYs from lower respiratory infections (acute bronchitis, pneumonia), 0.80 million from ear infections, and 3.86 million from chest infections and tuberculosis globally among children.

The researchers found that SHS continues to pose a serious health risk to children worldwide, but is particularly problematic in poorer regions, where the rates of disease burden (measured in DALYs) were much higher.

Regions that score highly on the Socio-demographic Index (SDI) reported age-standardised DALY rates of 7.64 and 10.25 per 100,000 children for lower respiratory infections and respiratory infections/tuberculosis, respectively, compared to low-SDI regions which showed rates of 302.43 and 305.40.

Dr Dai explained: “The impact of second-hand smoke on children’s respiratory health remains severe, but in some parts of the world, children are suffering even more than in others. Children in lower-SDI regions bear a disproportionate share of this preventable health burden. This likely reflects a combination of factors such as lower public awareness about the dangers of second-hand smoke, more overcrowded and poorly ventilated homes, and weaker tobacco control policies. These conditions may lead to higher exposure for children.

“In 2021 alone, exposure to second-hand smoke was linked to nearly 8.45m years of healthy life lost due to respiratory infections and tuberculosis, highlighting a preventable burden that falls most heavily on the least developed areas. Children are losing all these years of healthy life, but this could be prevented if they were protected from other people's smoke,” she added.

Dr Dai plans to carry out further analyses of SHS-related respiratory disease burden based on age, gender, and other factors, to support more precise and targeted interventions in the near future.

Dr Filippos Filippidis, Chair of the European Respiratory Society’s tobacco control committee, based at Imperial College, London, UK, who was not involved in the research said: "Around the world, hundreds of millions of people are still smoking and many are being exposed to second-hand smoke. Sadly, children often suffer the most as their lungs are still developing and they cannot avoid smoking in the home.

"This study quantifies the enormous harm children are suffering from second-hand smoke around the world. It is a wake-up call that we need to do much more to protect children. In particular, we need to create and enforce laws that limit smoking in places where children live or go to school. However, the most efficient approach is to reduce smoking across all age groups, which would substantially limit second-hand smoke exposure for children as well.

"As tobacco companies intensify marketing of emerging products, such as e-cigarettes and heated tobacco, it is also important to explore how these may indirectly affect children's health when they are exposed to second-hand vapours."

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Method of Research

Observational study

Subject of Research

People

Map showing the global distribution of DALYs attributable to SHS among children under 14 years of age, across four major disease categories

Credit

Siyu Dai/ERS

LEGALIZE DRUGS AVOID OD'S

Ketamine deaths increase twenty-fold since 2015 with mixing drugs on the rise

King's College London

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Deaths due to illicit ketamine use have increased twenty-fold since 2015 – but these deaths are increasingly occurring in complex polydrug settings, raising doubts over whether single-substance drug policies can reduce harms.

Analysis by King’s College London, with the University of Hertfordshire and Manchester Metropolitan University, of coroner’s reports in England, Wales and Northern Ireland between 1999 and 2024 found there were 696 deaths with detections of illicit ketamine between 1999 and 2024.  It represents the most detailed assessment to date of ketamine-related deaths in England, Wales, and Northern Ireland.

Ketamine is a Class B anaesthetic drug that has hallucinogenic effects. It’s cheap cost – around £15-30 for a gram compared to £80 for cocaine – could be driving increased consumption say researchers.

The number of people using ketamine in England and Wales has continued to rise with an estimated 299,000 people aged 16-59 reporting illicit ketamine use in 2024. The drug has been implicated in the deaths of celebrities, including Friends actor Matthew Perry, and Elon Musk is reported to use ketamine for his moods.

Whilst annual deaths with post-mortem detections of illicit ketamine have risen over the past decade, the proportion of deaths where ketamine was the sole or primary cause has fallen, reflecting a shift towards increasingly risky patterns of polydrug use. Opioids, cocaine, benzodiazepines, and gabapentinoids were frequently co-implicated in deaths, with the average number of substances involved in each case also rising.

The study also identified a demographic shift. While harms of ketamine use among young people – such as bladder injury and dependence – remain a serious concern, deaths are increasingly occurring among older, socioeconomically disadvantaged, and dependent drug users, rather than being confined to younger recreational populations.

Dr Caroline Copeland, lead author of the study from King’s College London and the Director of the National Programme on Substance Use Mortality said: “We are seeing more ketamine-related deaths, but these deaths rarely involve ketamine alone. They are increasingly part of complex polydrug use patterns, often among people facing social disadvantage and entrenched drug dependence. This means single-drug policies, such as reclassification, are unlikely to tackle the real drivers of harm.”

The study published today in Journal of Psychopharmacology also shows 85% of the deaths between 2020 and 2024 were men. Employment status was reported for 77% of the deaths between 2020 and 2024, with 42% employed, 42% unemployed and 11% students. The demographic profile of deaths shifted towards greater deprivation from 2020 to 2024. Death was deemed accidental in 88.9% of cases with 5.9% determined as suicidal.

The authors call for a more comprehensive response to address ketamine-related harms, including: expanded drug checking services and overdose prevention schemes, better integration of ketamine users into treatment pathways, and targeted education on the risks of polydrug use.

Ketamine can be prescribed medically as a sedative and is commonly used on animals. But when ketamine is misused, it can cause serious and sometimes irrevocable damage to the bladder. Mixing ketamine – a dissociative – with depressant drugs like opioids and benzodiazepines makes it harder to judge the effect each drug is having, which can result in people taking more of each drug than intended.

Dr Caroline Copeland added: “Illicit ketamine use has moved beyond the recreational setting. To reduce deaths, we need harm reduction, treatment, and social support strategies that reflect the realities of polydrug use – not just legislative changes focused on one substance”.

‘Deaths following illicit ketamine use in England, Wales and Northern Ireland 1999-2024: An update report to inform the reclassification debate’ is published in the Journal of Psychopharmacology.

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Journal

Journal of Psychopharmacology

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