Humans are the elephant in the room where conservation is debated

MICHIGAN STATE UNIVERSITY

 

IMAGE: 

A BEAR IN FRAZER LAKE, ALASKA, PUTS A FINER POINT ON THE INTERSECTION OF PEOPLE AND NATURE.

view more 

CREDIT: VERONICA FRANS, MICHIGAN STATE UNIVERSITY

Humans are outsized actors in the world’s wild places where there are struggles to preserve and protect vital natural resources and animals, birds and plants. Yet people and their plus-sized footprint are rarely discussed in models seeking to predict and plan for trajectories of endangered species.

Sustainability scholars at Michigan State University in this week’s journal Nature Ecology and Evolution reveal the decades-long gaps in research and propose a new way of creating accurate visions for endangered species.

To map and predict species geographic distributions around the globe and understand the factors that drive them, ecologists, conservation biologists and others use powerful computational tools called species distribution models (SDMs). These tools are used for conservation, understanding disease spread, food security, policy planning, and many other applications. To inform their predictions, scientists typically include the surrounding environment, such as climate and natural habitat.

But according to PhD candidate Veronica Frans, “we have a new reality that must be recognized if we want SDM predictions to be realistic and most helpful: we live in a human-dominated world.”

Frans and her advisor Jianguo “Jack” Liu, Rachel Carson chair in sustainability and director of MSU’s Center for Systems Integration and Sustainability, reviewed and synthesized 12,854 published studies covering over 58,000 species around the world, modeled across local to global spatial scales. They found that only 11 percent of those studies included human activities – which Frans said doesn’t reflect reality.

“Nearly half the articles projecting to future climates held human predictors constant over time,” Frans said. “That’s risking false optimism about the effects of human activities compared to climate change.”

They also found how scientists have been considering the future: nearly half of the SDM studies predicting species distributions have used different future climate scenarios but left data related to human activities constant over time. This means that modelers trying to understand where species will be distributed in the next 50 to 100 years were assuming human activities, development, infrastructure, and other human pressures will not change in the future.

“In our current era, human influence is pervasive and human-species interactions are diversifying and amplifying, and yet it is not being well accounted for in one of the most popular modeling tools in ecology,” Frans said.

They noted that modelers haven’t had a choice in the matter: geographic data on future human development have been sparse.

“This is an important aspect we must work to improve, since nature and humans are tightly linked, not only locally, but also across long distances” Liu said. “They form metacoupled human and natural systems. We will only be able to make significant and swift progress toward global sustainability when we consider all aspects of our real world.”

The article “Gaps and opportunities in modeling human influence on species distributions in the Anthropocene,” was funded by the National Science Foundation and Michigan AgBioResearch.

---

JOURNAL

Nature Ecology & Evolution

DOI

10.1038/s41559-024-02435-3 

METHOD OF RESEARCH

Literature review

ARTICLE TITLE

Gaps and opportunities in modeling human influence on species distributions in the Anthropocene

ARTICLE PUBLICATION DATE

12-Jun-2024

 

APA poll finds younger workers feel stressed, lonely and undervalued

Nearly one-third of U.S. workers prefer working with people their own age

AMERICAN PSYCHOLOGICAL ASSOCIATION

Younger workers are struggling with feelings of loneliness and a lack of appreciation at work and tend to feel more comfortable working with people their own age, according to a survey by the American Psychological Association.

The 2024 Work in America survey, conducted online by The Harris Poll of more than 2,000 working U.S. adults, found that three in 10 U.S. workers reported that people in their organization who are not close to their age do not see the value in their ideas (32%). That number was significantly higher for workers aged 18-25 (48%) than for workers aged 65 and older (16%). Workers aged 18-25 and 26-43 were also significantly more likely than workers aged 44-57, 58-64 and 65+ to say that they feel more comfortable working with people their own age than with other age groups (62% and 57% vs. 42%, 38% and 27%).

While most working adults reported that they appreciate the opportunity to work with people of different ages (92%) and say that having colleagues from a range of age groups is an advantage for their workplace (87%), a quarter said that they are worried about job security because of their age. And nearly three in 10 U.S. workers (29%) said that they feel self-conscious about their age at work, including 43% of workers aged 18-25.

There are signs that younger workers may have difficulty connecting with their coworkers on a personal level as well; nearly half (45%) of workers aged 18-25 said they feel lonely when they are working, significantly more than workers aged 26-43 (33%), 44-57 (22%), 58-64 (15%) and 65+ (14%). They are also more likely than older workers to say they typically feel tense or stressed out during their workday (48% aged 18-25, 51% aged 26-43, and 42% aged 44-57 vs. 30% aged 58-64 and 17% aged 65+).

“With more workers retiring later in life, the demographics of the workplace are changing and younger workers seem to be having the hardest time adjusting. At the same time, with increased remote work and the use of new technologies like AI, younger and older workers alike are facing a paradigm shift around where and how we work,” said Arthur C. Evans Jr., PhD, APA’s chief executive officer. “To remain competitive, employers should invest in strategies that support their workers’ well-being and mental health to help them navigate these new norms and evolving professional landscape.”

Overall, a third of U.S. workers said they do not have enough control over when, where and how they do their work. One in three workers (33%) also said they are not working in their preferred location, be it remote, in person or a hybrid of the two. According to the survey, 59% of U.S. workers reported currently working all in person, 24% reported being hybrid and 17% reported working completely remotely. However, only 38% of workers reported they would prefer to work all in person, compared with 34% who reported preferring to work hybrid and 28% who reported preferring to work remotely.

Other key findings:

• The percentage of workers who reported that their employer offers four-day workweeks was significantly higher in 2024 than the previous two years (14% in 2022, 17% in 2023 and 22% in 2024). And two-thirds (67%) said they believe the four-day workweek will become standard in their lifetime.
• Employees’ use of AI is outpacing employer guidance, with more than one-third of workers (35%) who reported using AI monthly or more often to assist with their work. However, only 18% reported knowing that their employer has an official policy about acceptable uses of AI. Half of workers said their employer has no such policy, and close to one-third (32%) were unsure.
• A majority (67%) of workers reported experiencing at least one outcome often associated with workplace burnout in the last month, such as lack of interest, motivation, or low energy, feeling lonely or isolated and a lack of effort at work.

What also stood out was that workers who feel comfortable expressing themselves or raising difficult issues without fear of negative consequences – what psychologists call “psychological safety” – tend to report better experiences at work. Workers who experience higher levels of psychological safety are more likely than workers experiencing lower levels of psychological safety to say they feel like they belong (95% vs. 69%) and that they feel comfortable being themselves in the workplace (95% vs. 75%). They were also 10 times less likely to say their workplace is very or somewhat toxic than workers who experience lower levels of psychological safety (3% vs. 30%).

The poll found that people with disabilities reported experiencing a lack of psychological safety at work at an alarming rate, which could be linked to the negative impacts of ableism or unequal access to opportunities due to bias. Two-thirds of workers with a cognitive, emotional, learning or mental disability and a similar number of workers with a physical disability (63%) reported experiencing lower levels of psychological safety, compared with 45% of workers who did not report having a disability.

Workers with disabilities were more likely to report concerns about their workplaces. Less than half (48%) of individuals living with a cognitive, emotional, learning or mental disability described their company’s culture as one that respects time off, compared with 63% of those not living with a disability. And 57% of workers with physical disabilities reported concern that AI may make some or all of their job duties obsolete in the near future, compared with 37% of workers who did not report having a disability.

“Our survey findings underscore the need for employers to create psychologically safe work environments for their employees,” Evans said. “We know from research that psychological safety not only enhances individual employee well-being but strengthens the organization by fostering a culture of creativity, innovation and effective teamwork, which ultimately helps to improve the bottom line.”

For more information from the latest Work in America survey, see the “2024 Work in America: Psychological Safety in the Changing Workplace” report.

Methodology

The research was conducted online in the United States by The Harris Poll on behalf of the American Psychological Association among 2,027 employed adults. The survey was conducted March 25-April 3, 2024. Data are weighted where necessary by age by gender, race/ethnicity, region, education, marital status, household size, work status, household income, and smoking status to bring them in line with their actual proportions in the population. A full methodology is available.

 

Eating small fish whole can prolong life expectancy, a Japanese study finds

NAGOYA UNIVERSITY

 

IMAGE: 

EATING SMALL FISH WHOLE CAN PROLONG LIFE EXPECTANCY, A JAPANESE STUDY FINDS

view more 

CREDIT: CHINATSU KASAHARA

A new study has found evidence linking the intake of small fish, eaten whole, with a reduced risk of all-cause and cancer mortality in Japanese women. Conducted by Dr. Chinatsu Kasahara, Associate Professor Takashi Tamura, and Professor Kenji Wakai at Nagoya University Graduate School of Medicine in Japan, the study highlights the potential life-extending benefits of habitually eating small fish. The findings were published in the journal Public Health Nutrition. 

Japanese people habitually eat small fish, such as whitebait, Atlantic capelin, Japanese smelt, and small dried sardines. Importantly, it is common practice to consume small fish whole, including the head, bones, and organs, which are rich in micronutrients, such as calcium and vitamin A.  

“Previous studies have revealed the protective effect of fish intake on health outcomes, including mortality risks. However, few studies have focused on the effect of the intake of small fish specifically on health outcomes,” said the lead researcher, Dr. Kasahara. “I was interested in this topic because I have had the habit of eating small fish since childhood. I now feed my children these foods.” 

The research team investigated the association between the intake of small fish and mortality risk among Japanese people. The study included 80,802 participants (34,555 men and 46,247 women) aged 35 to 69 years nationwide in Japan. The participants' frequency of the intake of small fish was assessed using a food frequency questionnaire at baseline. The researchers followed them for an average of nine years. During the follow-up period, 2,482 deaths from people included in the study were recorded, with approximately 60% (1,495 deaths) of them being cancer related. 

One of the most striking findings of the study was the significant reduction in all-cause and cancer mortality among women who habitually eat small fish. Women who eat small fish 1-3 times a month, 1-2 times a week, or 3 times or more a week had 0.68, 0.72, and 0.69 times the risk of all-cause mortality, and 0.72, 0.71, and 0.64 times the risk of cancer mortality, compared to those who rarely eat small fish. 

After controlling for factors that can affect mortality risk, such as participants' age, smoking and alcohol consumption habits, BMI, and intake of various nutrients and foods, the researchers found that women in the study who eat small fish frequently were less likely to die from any cause. These findings suggest that incorporating small fish into their daily diet could be a simple but effective strategy to reduce the risk of mortality among women.  

The risk of all-cause and cancer mortality in men showed a similar trend to that in women, although it was not statistically significant. The reasons for the lack of significance in men remain unclear, but the researchers posit that the limited number of male subjects or other factors not measured in the study, such as the portion size of small fish, may also matter. According to the researchers, the difference in the cancer type causing cancer mortality among sexes may be related to a sex-specific association. 

Although acknowledging the need for additional research in other populations and a deeper understanding of the mechanisms involved, Dr. Kasahara is enthusiastic about the results. “While our findings were only among Japanese people, they should also be important for other nationalities,” she said. 

In fact, previous studies have highlighted affordable small fish as a potentially important source of nutrients, especially in developing countries that suffer from severe nutrient deficiency. This study adds to the growing body of evidence supporting the health benefits of dietary practices that include eating small fish. As Dr. Kasahara explained, “Small fish are easy for everyone to eat, and they can be consumed whole, including the head, bones, and organs. Nutrients and physiologically active substances unique to small fish could contribute to maintaining good health. The inverse relationship between the intake of small fish and the mortality risk in women underscores the importance of these nutrient-dense foods in people's diets.” 

 “The habit of eating small fish is usually limited to several coastal or maritime countries, such as Japan,” Associate Professor Tamura said. “However, we suspect that the intake of small fish anywhere may be revealed as a way to prolong life expectancy. Further evidence is necessary to elucidate the potential role of the intake of small fish in mortality risk.” 

---

JOURNAL

Public Health Nutrition

DOI

10.1017/S1368980024000831 

 

A new weapon in the battle against antibiotic resistance: Temperature

UNIVERSITY OF GRONINGEN

 

IMAGE: 

COLONIES OF THE BACTERIUM E. COLI GROWING ON AN AGAR PLATE CONTAINING CIPROFLOXACIN: THESE RESISTANT COLONIES ORIGINATE FROM MUTANTS. ON THE LEFT THE RESISTANT MUTANTS ORIGINATING FROM A POPULATION GROWN AT 37 °C (NORMAL BODY TEMPERATURE), ON THE RIGHT RESISTANT MUTANTS ORIGINATING FROM A POPULATION GROWN AT 40 °C (FEVER TEMPERATURE).

view more 

CREDIT: ELEANOR SHERIDAN / UNIVERSITY OF GRONINGEN

Scientists from the University of Groningen (the Netherlands), together with colleagues from the University of Montpellier (France) and the University of Oldenburg (Germany), have tested how a fever could affect the development of antimicrobial resistance. In laboratory experiments, they found that a small increase in temperature from 37 to 40 degrees Celsius drastically changed the mutation frequency in E. coli bacteria, which facilitates the development of resistance. If these results can be replicated in human patients, fever control could be a new way to mitigate the emergence of antibiotic resistance. The results were published in the journal JAC-Antimicrobial Resistance.

Antimicrobial resistance of pathogens is a worldwide problem, and recognized by the WHO as one of the top global public health and development threats. There are two ways to fight this: by developing new drugs, or by preventing the development of resistance. ‘We know that temperature affects the mutation rate in bacteria’, explains Timo van Eldijk, co-first author of the paper. ‘What we wanted to find out was how the increase in temperature associated with fever influences the mutation rate towards antibiotic resistance.’

Three antibiotics

‘Most studies on resistance mutations were done by lowering the ambient temperature, and none, as far as we know, used a moderate increase above normal body temperature,’ Van Eldijk reports. Together with Master’s student Eleanor Sheridan, Van Eldijk cultured E. coli bacteria at 37 or 40 degrees Celsius, and subsequently exposed them to three different antibiotics to assess the effect. ‘Again, some previous human trials have looked at temperature and antibiotics, but in these studies the type of drug was not controlled.’ In their laboratory study, the team used three different antibiotics with different modes of action: ciprofloxacin, rifampicin, and ampicillin.

The results showed that for two of the drugs, ciprofloxacin and rifampicin, increased temperature led to an increase in the mutation rate towards resistance. However, the third drug, ampicillin, caused a decrease in the mutation rate towards resistance at fever temperatures. ‘To be certain of this result, we actually replicated the study with ampicillin in two different labs, at the University of Groningen and the University of Montpellier, and got the same result,’ says Van Eldijk.

Fever-suppressing drugs

The researchers hypothesized that a temperature dependence of the efficacy of ampicillin could explain this result, and confirmed this in an experiment. This explains why ampicillin resistance is less likely to arise at 40 degrees Celsius. ‘Our study shows that a very mild change in temperature can drastically change the mutation rate towards resistance to antimicrobials,’ concludes Van Eldijk. ‘This is interesting, as other parameters such as the growth rate do not seem to change.’

If the results are replicated in humans, this could open the way to tackling antimicrobial resistance by lowering the temperature with fever-suppressing drugs, or by giving patients with a fever antimicrobial drugs with higher efficacy at higher temperatures. The team concludes in the paper: ‘An optimized combination of antibiotics and fever suppression strategies may be a new weapon in the battle against antibiotic resistance.’

Reference: Timo J. B. Van Eldijk, Eleanor A. Sheridan, Guillaume Martin, Franz J. Weissing, Oscar P. Kuipers, G. Sander Van Doorn: Temperature dependence of the mutation rate towards antibiotic resistance/ JAC-Antimicrobial Resistance, 6 June 2024.

---

JOURNAL

JAC-Antimicrobial Resistance

DOI

10.1093/jacamr/dlae085 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Temperature dependence of the mutation rate towards antibiotic resistance

 

Vitamin B6: New compound delays degradation

UNIVERSITY OF WÜRZBURG

Vitamin B6 is important for brain metabolism. Accordingly, in various mental illnesses, a low vitamin B6 level is associated with impaired memory and learning abilities, with a depressive mood, and even with genuine depression. In older people, too little vitamin B6 is linked to memory loss and dementia.

Although some of these observations were made decades ago, the exact role of vitamin B6 in mental illness is still largely unclear. What is clear, however, is that an increased intake of vitamin B6 alone, for example in the form of dietary supplements, is insufficient to prevent or treat disorders of brain function.

Publication in eLife

A research team from Würzburg University Medicine has now discovered another way to increase vitamin B6 levels in cells more effectively: namely by specifically inhibiting its intracellular degradation. Antje Gohla, Professor of Biochemical Pharmacology at the Department of Pharmacology and Toxicology at Julius-Maximilians-Universität Würzburg (JMU), is responsible for this.

Other participants come from the Rudolf Virchow Center for Integrative and Translational Bioimaging at JMU, the Leibniz-Forschungsinstitut für Molekulare Pharmakologie-FMP Berlin and the Institute for Clinical Neurobiology at Würzburg University Hospital. The team has now published the results of their investigations in the scientific journal eLife.

Enzyme Blockade Improves Learning Ability

"We were already able to show in earlier studies that genetically switching off the vitamin B6-degrading enzyme pyridoxal phosphatase in mice improves the animals' spatial learning and memory capacity," explains Antje Gohla. In order to investigate whether such effects can also be achieved by pharmacological agents, the scientists have now looked for substances that bind and inhibit pyridoxal phosphatase.

With success: "In our experiments, we identified a natural substance that can inhibit pyridoxal phosphatase and thus slow down the degradation of vitamin B6," explains the pharmacologist. The working group was actually able to increase vitamin B6 levels in nerve cells that are involved in learning and memory processes. The name of this natural substance: 7,8-Dihydroxyflavone.

New Approach for Drug Therapy

7,8-Dihydroxyflavone has already been described in numerous other scientific papers as a molecule that can improve learning and memory processes in disease models for mental disorders. The new knowledge of its effect as an inhibitor of pyridoxal phosphatase now opens up new explanations for the effectiveness of this substance. This could improve the mechanistic understanding of mental disorders and represent a new drug approach for the treatment of brain disorders, the scientists write in their study.

The team also considers it a great success that 7,8-Dihydroxyflavone has been identified as an inhibitor of pyridoxal phosphatase for the first time - after all, this class of enzymes is considered to be particularly challenging for drug development.

A Long Way to a Drug

When will people benefit from this discovery? "It's too early to say," explains Marian Brenner, a first author of the study. However, there is much to suggest that it could be beneficial to use vitamin B6 in combination with inhibitors of pyridoxal phosphatase for various mental disorders and neurodegenerative diseases.

In a next step, Gohla and her team now want to develop improved substances that inhibit this enzyme precisely and highly effectively.  Such inhibitors could then be used to specifically test whether increasing cellular vitamin B6 levels is helpful in mental or neurodegenerative diseases.

---

JOURNAL

eLife

DOI

10.7554/eLife.93094.3 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

7,8-Dihydroxyflavone is a direct inhibitor of human and murine pyridoxal phosphatase

ARTICLE PUBLICATION DATE

10-Jun-2024

COI STATEMENT

A.G. is a recipient of a research project grant from Boehringer Ingelheim International GmbH. This project funding is independent of and has no overlap with the work described in this manuscript

 

An earthquake changed the course of the Ganges. Could it happen again?

A densely populated region could see cascading effects of shaking

Peer-Reviewed Publication

COLUMBIA CLIMATE SCHOOL

 

IMAGE: 

THE LOWLANDS OF BANGLADESH ARE IN MANY PLACES AN ELABORATE MIXTURE OF LAND AND WATER THAT SOMETIMES CHANGE PLACES. 

view more 

CREDIT: PHOTO BY STEVE GOODBRED

A major earthquake 2,500 years ago caused one of the largest rivers on Earth to abruptly change course, according to a new study. The previously undocumented quake rerouted the main channel of the Ganges River in what is now densely populated Bangladesh, which remains vulnerable to big quakes. The study was just published in the journal Nature Communications.

Scientists have documented many river-course changes, called avulsions, including some in response to earthquakes. However, “I don’t think we have ever seen such a big one anywhere,” said study coauthor Michael Steckler, a geophysicist at Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School. It could have easily inundated anyone and anything in the wrong place at the wrong time, he said.

Lead author Liz Chamberlain, an assistant professor at the Netherlands’ Wageningen University, said, “It was not previously confirmed that earthquakes could drive avulsion in deltas, especially for an immense river like the Ganges.”

The Ganges rises in the Himalayas and flows for some 1,600 miles, eventually combining with other major rivers including the Brahmaputra and the Meghna to form a labyrinth of waterways that empty into a wide stretch of the Bay of Bengal spanning Bangladesh and India. Together, they form the world’s second-largest river system as measured by discharge. (The Amazon is first.)

Like other rivers that run through major deltas, the Ganges periodically undergoes minor or major course changes without any help from earthquakes. Sediments washed from upstream settle and build up in the channel, until eventually the river bed grows subtly higher than the surrounding flood plain. At some point, the water breaks through and begins constructing a new path for itself. But this does not generally happen all at once—it may take successive floods over years or decades. An earthquake-related avulsion, on the other hand, can occur more or less instantaneously, said Steckler.

In satellite imagery, the authors of the new study spotted what they say was probably the former main channel of the river, some 100 kilometers south of the Bangladeshi capital of Dhaka. This is a low-lying area about 1.5 kilometers wide that can be found intermittently for some 100 kilometers more or less parallel to the current river course. Filled with mud, it frequently floods, and is used mainly for rice cultivation.

Chamberlain and other researchers were exploring this area in 2018 when they came across a freshly dug excavation for a pond that had not yet been filled with water. On one flank, they spotted distinct vertical dikes of light-colored sand cutting up through horizontal layers of mud. This is a well-known feature created by earthquakes: In such watery areas, sustained shaking can pressurize buried layers of sand and inject them upward through overlying mud. The result: literal sand volcanoes, which can erupt at the surface. Called seismites, here, they were 30 or 40 centimeters wide, cutting up through 3 or 4 meters of mud.

Further investigation showed the seismites were oriented in a systematic pattern, suggesting they were all created at the same time. Chemical analyses of sand grains and particles of mud showed that the eruptions and the abandonment and infilling of the channel both took place about 2,500 years ago. Furthermore, there was a similar site some 85 kilometers downstream in the old channel that had filled in with mud at the same time. The authors’ conclusion: This was a big, sudden avulsion triggered by an earthquake, estimated to be magnitude 7 or 8.

The quake could have had one of two possible sources, they say. One is a subduction zone to the south and east, where a huge plate of oceanic crust is shoving itself under Bangladesh, Myanmar and northeastern India. Or it could have come from giant splay faults at the foot of the Himalayas to the north, which are slowly rising because the Indian subcontinent is slowly colliding with the rest of Asia. A 2016 study led by Steckler shows that these zones are now building stress, and could produce earthquakes comparable to the one 2,500 years ago. The last one of this size occurred in 1762, producing a deadly tsunami that traveled up the river to Dhaka. Another may have occurred around 1140 CE.

The 2016 study estimates that a modern recurrence of such a quake could affect 140 million people. “Large earthquakes impact large areas and can have long-lasting economic, social and political effects,” said Syed Humayun Akhter, vice-chancellor of Bangladesh Open University and a coauthor on both studies.

The Ganges is not the only river facing such hazards. Others cradled in tectonically active deltas include China’s Yellow River; Myanmar’s Irrawaddy; the Klamath, San Joaquin and Santa Clara rivers, which flow off the U.S. West Coast; and the Jordan, spanning the borders of Syria, Jordan, the Palestinian West Bank and Israel.

Other coauthors of the new study are at the University of Cologne, Germany; the University of Dhaka; Bangladesh University of Professionals; Noakhali Science and Technology University, Bangladesh; and the University of Salzburg, Austria. The research was funded by the U.S. National Science Foundation.

A classic sign of a landscape disrupted by an earthquake: a vein of sand that has been pushed up through darker-colored sediments. 

CREDIT

Photo by Liz Chamberlain

More information: Columbia Climate School senior editor, science news kevin Krajick  kkrajick@climate.columbia.edu   +1 917-361-7766

---

JOURNAL

Nature Communications

DOI

10.1038/s41467-024-47786-4 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Cascading hazards of a major Bengal basin earthquake and abrupt avulsion of the Ganges River

ARTICLE PUBLICATION DATE

17-Jun-2024

 

Estimating the energy of past earthquakes from brecciation in a fault zone

TOHOKU UNIVERSITY

 

IMAGE: 

THE ICHINOKAWA MINE. AN OUTCROP ALONG THE RIVER RECORDS BRECCIATION BY EARTHQUAKES.

view more 

CREDIT: NORIYOSHI TSUCHIYA

During a 2017 research field trip to the Ichinokawa Mine (Ehime prefecture), which is famous for beautiful, sword-shaped stibnite crystals, Noriyoshi Tsuchiya found something unexpected. Although most would be entranced by the glittering crystals, it was a sedimentary rock bundle called breccia that caught his eye.

"I could not stop thinking about the breccia," Tsuchiya (professor at the Graduate School of Environmental Studies, and the Hachinohe National College of Technology) explains, "We visited the mine several times and discovered that the breccia records the traces of earthquakes and provides valuable evidence to estimate the energy of past earthquakes."

In the same way that the number of rings in a tree can tell us its age, the characteristics of rocks such as breccia can tell us about the history of a region. The Ichinokawa breccia are unique in that they can retain a record of the frequent seismic activity that occurs along the Median Tectonic Line (MTL). The MTL is a fault line that extends approximately 1000 kilometres along the southwest region of Japan. This makes the breccia formed in this area to be of particular interest to researchers.

In this study, Tsuchiya and their team assessed fragmented rocks both in the field and in the lab by extracting sections (slices so thin that they allow light to penetrate) from the collected rocks to observe under a microscope. The energy dissipated by the past earthquake was successfully estimated on the basis of statistical and fractal analyses of angular deformation and the powdery texture of rocks from a micro to macro scale.

It was found that the surface energy required to explain the naturally occurring distribution of fractured rocks was considerably greater (about 100 times greater) than the surface energy required from a single impact fracture experiment on a rock performed in the laboratory.

Many factors were assessed in order to calculate the energy and nature of the earthquake. For example, close observation of breccia revealed the formation of carbonates such as CaMg(CO3)2. Since the host rock that broke off did not contain any carbonates, it was deduced that this mineral must have formed after the formation of breccia. They concluded that the earthquake did not occur just once, but repeatedly, and that caused the fine particles to be crushed into even finer particles. Their findings suggest the Ichinokawa breccia were formed by 10-100 earthquakes with a moment magnitude (an index of seismic energy) estimated to be 5.8-8.3 Mw.

Further analysis revealed that the breccia had a very unique pattern of fragmentation (or pulverization). "Previous models designed to explain the earthquake history use a different theory, based primarily on hydrofracturing. However, we adopted a multi-disciplinary approach, so our analysis can be used to propose a new model that takes more factors into account" Tsuchiya adds.

This study, which was a collaboration with the National Institute of Technology and Hachinohe College, may redefine our understanding of the coseismic energy budget in this region.

These findings were published in Scientific Reports on May 27, 2024.

Photo of breccia with wide particle size distribution and in situ fragmentation.

sion of particle size distribution. 

The matrix component and dolomite composition (f) Relative abundance of the matrix. (a-c) The dolomite profile within the matrix shows the variation of Mg and Fe corresponding to five oscillatory zoning under backscattered image (BSE). A thin-section scan with a red-dashed square indicates the areas analyzed for a couple of analyses in this study. 

CREDIT

Noriyoshi Tsuchiya

JOURNAL

Scientific Reports

DOI

10.1038/s41598-024-62838-x 

ARTICLE TITLE

Multiscale off-fault brecciation records coseismic energy budget of principal fault zone