The group headed by Hongyu Yu – first at RUB, later at the Canadian Geological Survey of Canada – and RUB Professor Rebecca Harrington describes the results in the journal Nature Communications, published online on 25 November 2021.

Several theories on the origins of earthquakes

To date, researchers have explained the occurrence of earthquakes in the hydraulic-fracturing process with two processes. The first says that the fluid pumped into the rock generates a pressure increase substantial enough to generate a new network of fractures in the subsurface rocks near the well. As a result, the pressure increase can be large enough to unclamp existing faults and trigger an earthquake. According to the second process, the fluid pressure increase from injection in the subsurface also exerts elastic stress changes on the surrounding rocks that can be transmitted over longer distances. If the stress changes occur in rocks where faults exist, it can also lead to changes that cause the fault to slip and cause an earthquake.

Recently, numerical models and lab analyses have predicted a process on faults near injection wells that has been observed elsewhere on tectonic faults. The process, termed aseismic slip, starts out as slow slip that does not release any seismic energy. The slow slip can also cause a stress change on nearby faults that causes them slip rapidly and lead to an earthquake. The lack of seismic energy from aseismic slip and the size of the faults involved make it difficult to observe in nature. Researchers have therefore not yet been able to document aseismic slip broadly with any association to induced earthquakes. The work of the current study, provides indirect evidence of aseismic loading, and a transition from aseismic to seismic slip.

Modifying the hydraulic fracturing process

The German-Canadian research team interpret the recently discovered slow earthquakes as an intermediate form of conventional earthquake and aseismic slip – and thus as indirect evidence that aseismic slip can also occur in the vicinity of wells. The researchers therefore dubbed the events hybrid-frequency waveform earthquakes (EHW).

“If we understand at which point the subsurface reacts to the hydraulic-fracturing process with movements that don’t result in an earthquake and, consequently, cause no damage to the surface, ideally we could use that information to adjust the injection procedure accordingly,” as Rebecca Harrington, Head of the Hydrogeomechanics Group at RUB, describes one implication of the study.

Not all quakes spread at the same rate

“We’d assumed that induced earthquakes behave like most other earthquakes and have roughly the same rupture speed of two to three kilometres per second,” explains Rebecca Harrington. But that doesn’t always seem to be the case. While the shaking from a conventional earthquake of magnitude 1.5 in the researchers’ data set had died down after about seven seconds, an EHW earthquake of the same magnitude continued to shake for more than ten seconds.

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Materials provided by Ruhr-University Bochum. Note: Content may be edited for style and length.

Prolonged sunny or rainy conditions lead to extreme events

To prove this, the scientists analysed the persistence of specific weather conditions. They applied established image comparison methods on atmospheric data, comparing millions of successive weather circulation patterns worldwide over the last 40 years. They especially looked at two individual extreme events, the 2010 heat wave over Russia and the extraordinary dry summer over Europe in 2018. “We found that weather patterns in general are more persistent now than some decades ago,” says Hoffmann. “Especially in summer, heat waves often last longer now, and also rainfall events tend to linger longer and to be more intense. The longer these weather conditions last, the more intense the extremes can become, both on the warm and dry side as well as on the steady rain side.”

The rise in persistent weather conditions is to a large extent due to dynamical changes in the atmosphere as the westerly winds tend to stop pushing forward weather systems which therefore become more persistent, turning some sunny days into heatwaves of several weeks as well as intensive rainfall into floods.

Climate models might underestimate rise in persistent weather patterns

Like the eye of a knowledgeable observer, the new image comparison method systematically scans atmospheric fields and helps to assess to which extent successive weather circulation patterns change over time or remain stable. Fred Hattermann, co-author of the study and also scientist at PIK, explains the potential of the new approach: “Our method crucially improves the interpretation of long-term climate impacts. When applying the same methodology to climate model output, we do not see a comparable increase in weather persistence, especially not over Europe. Climate models may have been a bit too conservative, underestimating the rise in weather persistence — thus underestimating weather extremes over Europe.” This becomes ever more important with ongoing climate change.

“Recent events and ongoing research have shown that the number and intensity of extreme events have increased due to the global rise in temperature,” concludes Hattermann. “To counteract this worrying trend, the goal has to be to reduce global greenhouse gas emissions and by doing so limit climate change.”

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Materials provided by Potsdam Institute for Climate Impact Research (PIK). Note: Content may be edited for style and length.

Glionitrin A and B are two molecules with properties that make them useful in drug development. However, researchers who want to use these molecules have faced an uphill battle for almost a decade.

Glionitrin A and B are natural products, and are produced a fungus found in extremely contaminated acidic wastewater from an abandoned South Korean mine. Since the fungus only creates the molecules when triggered by specific bacteria from the same sewage, it has proved difficult to produce .

“We have been working on this problem for four years. Every time we thought we had a solution, the molecules revealed unexpected properties that sent us back to the drawing board,” says Daniel Strand, chemistry researcher at Lund University.

Despite the complex nature of the problem, the solution proved to be both simpler and more effective than the researchers thought. By developing a new so-called asymmetric organocatalytic reaction, Daniel Strand and his colleagues succeeded in the most inaccessible parts of the molecules.

“we thought the problem was solved, the molecule had one last surprise. It turned out that the real structure was the mirror image of we initially thought was glionitrin A. So, all this time we had chased a molecule that ,” says Daniel Strand.

Complex natural products with unique properties such as glionitrin A and B are important tools in develop.

Glionitrin A has shown antibiotic properties against resistant bacteria, while glionitrin B makes cancer cells less to migrate. Being able to produce the molecules synthetically helps researchers not only understand how they work, but also improve their properties.

“There is a great need for new types of antibiotics, especially those that can contribute to the fight against resistant bacteria. We expect our results to inspire further development basic synthetic chemistry but also to be used in drug development,” concludes Daniel Strand.

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Materials provided by Lund University. Note: Content may be edited for style and length.