How to distinguish slow and fast earthquakes

Researchers from the University of Tokyo and Stanford University show what differentiates slow and fast earthquakes and how their magnitudes vary with time.

Normally, earthquakes last up to a few minutes and radiate strong seismic waves. But around 23 years ago, scientists discovered an unusual slow-slip phenomena called slow earthquakes. Slow earthquakes last days or even months. Though they involve significant tectonic movement, you may never feel them. Since slow earthquakes could indicate future fast earthquakes, monitoring and understanding them helps accurately forecast devastating earthquakes and tsunamis.

Understanding them requires knowing how they change over time. For that, researchers use scaling laws which define the relationship between two quantities over a wide interval. In 2007, researchers proposed a controversial scaling law relating the magnitude and duration of earthquakes, which can help differentiate slow and fast earthquakes.

According to the scaling law, for slow earthquakes, as its magnitude (measured by a quantity called seismic moment) increases, the duration of the earthquake increases proportionately. For fast earthquakes, the relation is not linearly but cubically proportionate, which means the seismic moment increases very rapidly in a short time.

The scaling law received criticism from other researchers and raised questions about the likelihood of events in between slow and fast earthquakes that do not fall within the law. Seismologists Satoshi Ide of the University of Tokyo and Gregory Beroza of Stanford University now bolster the scaling law with more data, reinterpret the scaling relation, and address the controversy.

"Most of the challenges to the scaling law were problematic, but we have had no chance to disprove their challenges," says Ide. "A surprise was that totally erratic results were published in Nature, and believed by many scientists, who made further problematic numerical models."

With the advent of new seismic detection technology and data accumulated over 16 years, Ide and Beroza now reason that most arguments against the law had improper data calculations and were inconsistent given their data constraints. They suggest the presence of a speed limit to slow earthquakes and reveal physical processes that differentiate slow and fast earthquakes.

Many, but all the same

Since slow earthquakes include phenomena with different frequency bands, they are more diverse than fast earthquakes. They were named differently, such as low-frequency earthquakes, tectonic tremors, very low-frequency earthquakes, and slow slip events. So researchers observing one type of slow earthquake considered other types irrelevant. "Our study confirmed that all these phenomena are mutually connected, or rather regarded as a single phenomenon that radiates various signals," explains Ide.

Slow slips, but not so fast

Slow earthquakes are so subtle and inaccessible that detecting and monitoring them is challenging. Due to the detection bias, only large enough slow earthquakes are observed. That prompted Ide and Beroza to propose an upper limit to the speed of slow earthquakes. Based on that, the duo redefined the 2007 scaling law with the maximum value constraint. As they showed continuous evidence for the scaling law over a broad time scale of less than a second to more than a year, they put an end to the debate.

How are slow and fast earthquakes different?

When Ide's group proposed the scaling law in 2007, they were unsure of what makes these two earthquake types different. Now, with more data and theoretical models, Ide and Beroza show that their scaling differences dictate physical movement processes governing the events. Diffusion processes govern slow earthquakes, whereas seismic wave propagation dictates fast earthquakes. Because of this difference, the magnitude of slow earthquakes cannot be as large as fast earthquakes when the event lasts longer.

"We pointed out that 'diffusion' is important in slow earthquakes, but what is physically diffusing is not well understood," says Ide.

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Sun 'umbrella' tethered to asteroid might help mitigate climate change

Earth is rapidly warming and scientists are developing a variety of approaches to reduce the effects of climate change. István Szapudi, an astronomer at the University of Hawaiʻi Institute for Astronomy, has proposed a novel approach -- a solar shield to reduce the amount of sunlight hitting Earth, combined with a tethered, captured asteroid as a counterweight. Engineering studies using this approach could start now to create a workable design that could mitigate climate change within decades.

The paper, "Solar radiation management with a tethered sun shield," is published in Proceedings of the National Academy of Sciences.

One of the simplest approaches to reducing the global temperature is to shade the Earth from a fraction of the Sun's light. This idea, called a solar shield, has been proposed before, but the large amount of weight needed to make a shield massive enough to balance gravitational forces and prevent solar radiation pressure from blowing it away makes even the lightest materials prohibitively expensive. Szapudi's creative solution consists of two innovations: a tethered counterweight instead of just a massive shield, resulting in making the total mass more than 100 times less, and the use of a captured asteroid as the counterweight to avoid launching most of the mass from Earth.

"In Hawaiʻi, many use an umbrella to block the sunlight as they walk about during the day. I was thinking, could we do the same for Earth and thereby mitigate the impending catastrophe of climate change?" Szapudi said.

Szapudi began with the goal of reducing solar radiation by 1.7%, an estimate of the amount needed to prevent a catastrophic rise in global temperatures. He found that placing a tethered counterbalance toward the Sun could reduce the weight of the shield and counterweight to approximately 3.5 million tons, about one hundred times lighter than previous estimates for an untethered shield.

While this number is still far beyond current launch capabilities, only 1% of the weight -- about 35,000 tons -- would be the shield itself, and that is the only part that needs to be launched from Earth. With newer, lighter materials, the mass of the shield can be reduced even further. The remaining 99% of the total mass would be asteroids or lunar dust used as a counterweight. Such a tethered structure would be faster and cheaper to build and deploy than other shield designs.

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Half the population to have a mental health disorder by 75

A global study co-led by researchers from The University of Queensland and Harvard Medical School has found one in two people will develop a mental health disorder in their lifetime.

Professor John McGrath from UQ's Queensland Brain Institute, Professor Ronald Kessler from Harvard Medical School, and their colleagues from 27 other countries, analysed data from more than 150,000 adults across 29 countries between 2001 and 2022, taken from the largest ever coordinated series of face-to-face interviews -- the World Health Organisation's World Mental Health Survey initiative.

Lead author Professor McGrath said the results demonstrate the high prevalence of mental health disorders, with 50 per cent of the population developing at least one disorder by the age of 75.

"The most common were mood disorders such as major depression or anxiety," Professor McGrath said.

"We also found the risk of certain mental disorders differed by sex."

The 3 most common mental health disorders among women:
 

• Depression
• Specific phobia (a disabling anxiety that interferes with daily life)
• Post-traumatic stress (PTSD)

The 3 most common mental health disorders among men:
 

• Alcohol abuse
• Depression
• Specific phobia

The research also found mental health disorders typically first emerge in childhood, adolescence or young adulthood.

"The peak age of first onset was at 15 years old, with a median age of onset of 19 for men and 20 for women," Professor McGrath said.

"This lends weight to the need to invest in basic neuroscience to understand why these disorders develop."

Professor Kessler said investment was also needed in mental health services with a particular focus on young people.

"Services need to be able to detect and treat common mental disorders promptly, and be optimised to suit patients in these critical parts of their lives," Professor Kessler said.

"By understanding the age at which these disorders commonly arise, we can tailor public health interventions and allocate resources to ensure that appropriate and timely support is available to individuals at risk."

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New clues on the source of the universe's magnetic fields

It isn't just your refrigerator that has magnets on it. The earth, the stars, galaxies, and the space between galaxies are all magnetized, too. The more places scientists have looked for magnetic fields across the universe, the more they've found them. But the question of why that is the case and where those magnetic fields originate from has remained a mystery and a subject of ongoing scientific inquiry.

A new paper by Columbia researchers offers insight into the source of these fields. The team used models to show that magnetic fields may spontaneously arise in turbulent plasma. Plasma is a kind of matter often found in ultra-hot environments like that near the surface of the sun, but plasma is also scattered across the universe in low-density environments, like the expansive space between galaxies; the team's research focused on those low-density environments. Their simulations showed that, in addition to generating new magnetic fields, the turbulence of those plasmas can also amplify magnetic fields once they've been generated, which helps explain how magnetic fields that originate on small scales can sometimes eventually reach to stretch across vast distances.

The paper was written by astronomy professor Lorenzo Sironi, astronomy research scientist Luca Comisso, and astronomy doctoral candidate Ryan Golant.

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Insolation affected ice age climate dynamics

In past ice ages, the intensity of summer insolation affected the emergence of warm and cold periods and played an important role in triggering abrupt climate changes, a study by climate researchers, geoscientists, and environmental physicists suggests. Using stalagmites in the European Alps, they were able to demonstrate that warm phases appeared primarily when the summer insolation reached maxima in the Northern Hemisphere. Study participants included scientists from Germany, Austria, and Switzerland led by researchers from Heidelberg University and the GFZ German Research Centre for Geosciences Potsdam.

Past ice ages in the Northern Hemisphere were marked by sudden transitions between cold and warm phases, each lasting several thousand years. The reason for these fluctuations has yet to be resolved, but research does point to effects relating to the size of the continental ice sheets. Greenland ice records 25 such warm-cold cycles between 115,400 and 14,700 years ago. Investigating stalagmites in the Melchsee-Frutt cave system in the Swiss Alps, the researchers were able to investigate for the first time and with high precision 16 such fluctuations in the penultimate glacial period 185,000 to 130,000 years ago.

Stalagmites in caves are crucial archives in climate research and offer clues as to changes in temperature, precipitation, and vegetation cover. "We are able to precisely determine their age and hence analyse the chronological sequence of abrupt ice age climate fluctuations, which we identify using oxygen isotope values," explains Prof. Dr Norbert Frank of the Institute of Environmental Physics at Heidelberg University. "Our investigations targeted whether, in addition to ice volumes in the Northern Hemisphere, orbitally driven changes in the global distribution of insolation could have influenced the abrupt changes in climate," states study head Dr Jens Fohlmeister, who earned his doctorate in environmental physics at Heidelberg University and worked at the GFZ German Research Centre for Geosciences Potsdam and the Potsdam Institute for Climate Impact Research during the investigations.

The researchers studied the transitions of warm-cold cycles in the penultimate ice age by analysing the age and oxygen isotope composition of stalagmites from the Melchsee-Frutt cave system. "Based on the newly acquired data, we were able to show that warm phases occurred mainly during the peak phase of summer insolation in the Northern Hemisphere, even when the sea level, which is dependent on the volume of the continental ice sheets, remained close to its minimum during peak glacial periods," explains Dr Fohlmeister. Model simulations confirmed these findings. In accordance with the research data from the cave system, the simulations predict the frequency as well as the duration of warm phases at the corresponding sea level and existing insolation.

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Researchers create total synthesis of HIV replication inhibitor

Having control over how a dish is cooked is always a good idea. Taking a hint from the kitchen, scientists appear to have discovered a way to produce a true structure of the rare but naturally-occurring anti-HIV compound Lancilactone C from start to finish.

Its non-cytotoxicity in mammals could make this triterpenoid an ideal candidate for treating AIDS if its biological activity were clear -- and if only it were abundant in nature.

Now, a research group at Kyoto University has succeeded in creating a domino-like synthesis of Lancilactone C's unique seven-membered ring structure.

"Our synthetic method revealed that the proposed structure of Lancilactone C was initially incorrect," says Chihiro Tsukano of Kyoto University's Graduate School of Agriculture. "But we successfully derived its true structure from our spectral data and understanding of its biosynthesis."

In addition to this revelation, Tsukano realized that the electrocyclization -- a rearrangement reaction in organic chemistry -- used in the total synthesis also occurs in biosynthesis. Ironically, it remains a mystery of whether the proposed structure containing an unsaturated seven-membered ring might exist in nature as an analog -- or equivalent compound -- and how it might affect the expression of biological activity.

Tsukano's team utilized the domino-like reaction to enable the total synthesis of lancilactones and related triterpenoids. This outcome has inspired the team to further their research in optimizing compound structures, leading to possible development of novel antivirals.

The endless loop of required medication and multi-drug therapies often correlates with a lower quality of life for economically burdened patients.

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Routinely drinking alcohol may raise blood pressure even in adults without hypertension

Even in adults without hypertension, blood pressure readings may climb more steeply over the years as the number of daily alcoholic drinks rise, according to an analysis of seven international research studies published today in Hypertension, an American Heart Association journal.

With the statistical power of seven international research studies, this analysis confirms for the first time there was a continuous increase in blood pressure measures in both participants with low and high alcohol intake. Even low levels of alcohol consumption were associated with detectable increases in blood pressure levels that may lead to a higher risk of cardiovascular events.

"We found no beneficial effects in adults who drank a low level of alcohol compared to those who did not drink alcohol," said senior study author Marco Vinceti, M.D., Ph.D., a professor of epidemiology and public health in the Medical School of the University of Modena and Reggio Emilia University in Italy and an adjunct professor in the department of epidemiology at Boston University's School of Public Health. "We were somewhat surprised to see that consuming an already-low level of alcohol was also linked to higher blood pressure changes over time compared to no consumption -- although far less than the blood pressure increase seen in heavy drinkers."

"Our analysis was based on grams of alcohol consumed and not just on the number of drinks to avoid the bias that might arise from the different amount of alcohol contained in 'standard drinks' across countries and/or types of beverages," said study co-author Tommaso Filippini, M.D., Ph.D., an associate professor of epidemiology and public health in the Medical School of the University of Modena and Reggio Emilia in Italy, and affiliate researcher at the University of California Berkeley School of Public Health.

Researchers reviewed the health data for all participants across the seven studies for more than five years. They compared adults who drank alcohol regularly with non-drinkers and found:
 

• Systolic (top number) blood pressure rose 1.25 millimeters of mercury (mm Hg) in people who consumed an average of 12 grams of alcohol per day, rising to 4.9 mm Hg in people consuming an average of 48 grams of alcohol per day. (In the U.S., 12 ounces of regular beer, 5 ounces of wine or a 1.5 ounce shot of distilled spirits contains about 14 grams of alcohol. Usual alcohol content differs in alcohol available in other countries.)
• Diastolic (bottom number) blood pressure rose 1.14 mm Hg in people consuming an average of 12 grams of alcohol per day, rising to 3.1 mm Hg in people consuming an average of 48 grams of alcohol per day. These associations were seen in males but not in females. Diastolic blood pressure measures the force against artery walls between heartbeats and is not as strong a predictor of heart disease risk in comparison to systolic.

"Alcohol is certainly not the sole driver of increases in blood pressure; however, our findings confirm it contributes in a meaningful way. Limiting alcohol intake is advised, and avoiding it is even better," Vinceti said.

Although none of the participants had high blood pressure when they enrolled in the studies, their blood pressure measurements at the beginning did have an impact on the alcohol findings.

"We found participants with higher starting blood pressure readings, had a stronger link between alcohol intake and blood pressure changes over time. This suggests that people with a trend towards increased (although still not "high") blood pressure may benefit the most from low to no alcohol consumption," said study co-author Paul K. Whelton, M.D., M.Sc., the Show Chwan Chair in Global Public Health in the department of epidemiology at Tulane University's School of Public Health and Tropical Medicine in New Orleans and president of the World Hypertension League. Whelton is also the chair of the American Heart Association's 2017 Hypertension Practice Guidelines and a member of the writing committee for the Association's 2021 Scientific Statement on Management of Stage 1 Hypertension in Adults.

According to American Heart Association recommendations, if you don't drink already, don't start. If you do drink, talk with your doctor about the benefits and risks of consuming alcohol in moderation. The Association also does not recommend drinking any form of alcohol to gain potential health benefits. Instead, follow the Association's lifestyle and health metrics for optimal cardiovascular health called Life's Essential 8: eat healthy food, be physically active, don't smoke, get enough sleep, maintain a healthy weight, and control cholesterol, blood sugar and blood pressure levels.

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Self-healing plastic becomes biodegradable

Imagine a plastic like this: harder than common plastics, non-flammable, and even with self-healing properties. But that is not all! It can be produced at room temperature in water, which is very energy-efficient and does not require toxic solvents. Before hardening, you can shape the plastic in any way you want -- like chewing gum. By adding water, it can also be converted back to its "chewing gum" form at any time, reshaped and thus recycled as often as desired.

Is that impossible? No, it is not! In 2016, the research team around Konstanz chemist Helmut Cölfen presented just such a material -- a mineral plastic. However, even though the plastic, with its novel manufacturing process and outstanding material properties, has since attracted great interest from industry, it still had a crucial shortcoming from the Konstanz chemists' point of view: due to its chemical composition, it was difficult to biodegrade.

A new ingredient for greater environmental compatibility

"Previously, we used polyacrylic acid to produce our mineral plastic. Chemically, this acid has the same backbone as polyethylene, which is known to cause major problems in the environment because it is hardly biodegradable," explains Cölfen. The research team led by Cölfen and Ilesha Avasthi, a postdoc in Cölfen's lab, therefore set to work looking for an alternative basic building block to develop an environmentally compatible mineral plastic that retains the intriguing properties of the original material. And they found what they were looking for.

In their current publication in the journal Small Methods, the Konstanz chemists present the next generation of their mineral plastic. Instead of petroleum-based ingredients such as polyacrylic acid, they now use polyglutamic acid. This natural biopolymer is readily available in large quantities and can even be obtained sustainably, for example from biotechnological production using microorganisms. A variety of microorganisms that already exist in the environment can degrade polyglutamic acid.

"Our new mineral plastic has the same positive properties as the previous one, but has the decisive advantage that its basic building block -- polyglutamic acid -- can be produced with the help of microorganisms and is completely biodegradable," says Helmut Cölfen.

Support from biologists

In order to prove that this biodegradability also applies to the new mineral plastic itself and not just to its individual components, the chemists enlisted the support of David Schleheck and postdoc Harry Lerner from the Department of Biology at the University of Konstanz. "Helmut Cölfen has created a new type of mineral plastic in his laboratory, and our task now was to make it disappear again with the help of microorganisms," says Schleheck with a smile.

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'Time-traveling' pathogens in melting permafrost pose likely risk to environment

Ancient pathogens that escape from melting permafrost have real potential to damage microbial communities and might potentially threaten human health, according to a new study by Giovanni Strona of the European Commission Joint Research Centre and colleagues, published July 27 in the open-access journal PLOS Computational Biology.

The idea that "time-traveling" pathogens trapped in ice or hidden in remote laboratory facilities could break free to cause catastrophic outbreaks has inspired generations of novelists and screenwriters. While melting glaciers and permafrost are giving many types of dormant microbes the opportunity to re-emerge, the potential threats to human health and the environment posed by these microbes have been difficult to estimate.

In a new study, Strona's team quantified the ecological risks posed by these microbes using computer simulations. The researchers performed artificial evolution experiments where digital virus-like pathogens from the past invade communities of bacteria-like hosts. They compared the effects of invading pathogens on the diversity of host bacteria to diversity in control communities where no invasion occurred.

The team found that in their simulations, the ancient invading pathogens could often survive and evolve in the modern community, and about 3 percent became dominant. While most of the dominant invaders had little effect on the composition of the larger community, about 1 percent of the invaders yielded unpredictable results. Some caused up to one third of the host species to die out, while others increased diversity by up to 12 percent compared to the control simulations.

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Gloomy climate calculation: Scientists predict a collapse of the Atlantic ocean current to happen mid-century

Important ocean currents that redistribute heat, cold and precipitation between the tropics and the northernmost parts of the Atlantic region will shut down around the year 2060 if current greenhouse gas emissions persist. This is the conclusion based on new calculations from the University of Copenhagen that contradict the latest report from the IPCC.

Contrary to what we may imagine about the impact of climate change in Europe, a colder future may be in store. In a new study, researchers from the University of Copenhagen's Niels Bohr Institute and Department of Mathematical Sciences predict that the system of ocean currents which currently distributes cold and heat between the North Atlantic region and tropics will completely stop if we continue to emit the same levels of greenhouse gases as we do today.

Using advanced statistical tools and ocean temperature data from the last 150 years, the researchers calculated that the ocean current, known as the Thermohaline Circulation or the Atlantic Meridional Overturning Circulation (AMOC), will collapse -- with 95 percent certainty -- between 2025 and 2095. This will most likely occur in 34 years, in 2057, and could result in major challenges, particularly warming in the tropics and increased storminess in the North Atlantic region.

"Shutting down the AMOC can have very serious consequences for Earth's climate, for example, by changing how heat and precipitation are distributed globally. While a cooling of Europe may seem less severe as the globe as a whole becomes warmer and heat waves occur more frequently, this shutdown will contribute to an increased warming of the tropics, where rising temperatures have already given rise to challenging living conditions," says Professor Peter Ditlevsen from the Niels Bohr Institute.

"Our result underscores the importance of reducing global greenhouse gas emissions as soon as possible," says the researcher.

The calculations, just published in the scientific journal, Nature Communications, contradict the message of the latest IPCC report, which, based on climate model simulations, considers an abrupt change in the thermohaline circulation very unlikely during this century.

Early warning signals present

The researchers' prediction is based on observations of early warning signals that ocean currents exhibit as they become unstable. These Early Warning Signals for the Thermohaline Circulation have been reported previously, but only now has the development of advanced statistical methods made it possible to predict just when a collapse will occur.

The researchers analysed sea surface temperatures in a specific area of the North Atlantic from 1870 to present days. These sea surface temperatures are "fingerprints" testifying the strength of the AMOC, which has only been measured directly for the past 15 years.

"Using new and improved statistical tools, we've made calculations that provide a more robust estimate of when a collapse of the Thermohaline Circulation is most likely to occur, something we had not been able to do before," explains Professor Susanne Ditlevsen of UCPH's Department of Mathematical Sciences.

The thermohaline circulation has operated in its present mode since the last ice age, where the circulation was indeed collapsed. Abrupt climate jumps between the present state of the AMOC and the collapsed state has been observed to happen 25 times in connection with iceage climate. These are the famed Dansgaard-Oeschger events first observed in ice cores from the Greenlandic ice sheet. At those events climate changes were extreme with 10-15 degrees changes over a decade, while present days climate change is 1.5 degrees warming over a century.

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