Scientists observed a ̵6;boomerang’ earthquake along the Atlantic Fault Line, providing clues as to how they could cause havoc on land.
An earthquake occurs when a rock suddenly breaks on a fault – the boundary between two blocks or plates. During major earthquakes, the break of rock can spread down the fault line. Now, an international team of researchers has recorded a ‘boomerang’ earthquake where the rupture initially spread out of the original breach but then turned and ran back in the other direction at a different speed. higher.
The intensity and duration of the fault along a fault affects the shaking of the ground on the surface, which can damage buildings or create a tsunami. Ultimately, knowing the mechanics of how the fracture and physics is involved will help researchers make better models and predictions about future earthquakes, and can also inform systems. earthquake early warning system.
The team, led by scientists from the University of Southampton and Royal University London, reported their results in Nature Geoscience is a monthly peer-reviewed scientific journal published by Nature Publishing Group that covers all aspects of Earth science, including theoretical research, modeling, and field research. Other related works are also published in fields including atmospheric science, geology, geophysics, climate, oceanography, paleontology and space science. It was established in January 2008.
“class =” glossaryLink “> Natural geoscience on August 10, 2020.
Break the seismic sound barrier
While large earthquakes (7 or greater) occur on land and have been measured with a nearby network of monitors (seismometers), these often trigger motion along the network. Complicated fault grid, like a chain of domino pieces. This makes it difficult to follow the basic mechanisms of how this ‘seismic slip’ occurs.
Under the ocean, many types of faults have a simple shape, so are likely to be under the bonnet of the ‘earthquake engine’. However, they are far from large land-based seismic networks. The team used a new underwater seismic network to track the Romanche fault zone, a fault line that spans 900 km below the Atlantic near the equator.
In 2016, they recorded a magnitude 7.1 earthquake along the Romanche fault zone and tracked the fault along the fault. This suggests that the fracture initially moves in one direction before spinning between the earthquake and breaks the ‘seismic sound barrier’, becoming an extremely fast earthquake.
Only a handful of such earthquakes have been recorded globally. The team believes that the first stage of the rupture is crucial in causing the second stage to slip quickly.
Provide earthquake forecasting
The study’s first author, Dr. Stephen Hicks, from the Department of Earth Science and Engineering at Imperial, said: “While the scientists discovered that such reverse fault mechanism could occur. Out of theoretical models, our new research provides some of the clearest evidence for this mysterious mechanism to occur in a real error.
“Although the fault structure looks simple, how the earthquake evolved, and this is quite the opposite of how we predicted the earthquake before we started analyzing the data.”
However, the team says that if similar types of boomerang or boomerang earthquakes could occur on land, a reverse seismic fault in the middle of an earthquake could have a significant effect. to the amount of ground shake caused.
Due to the lack of previously observed evidence, this mechanism is not used in earthquake scenario modeling and the assessment of risks from such earthquakes. Boomerang earthquake detail tracking could allow researchers to find similar patterns in other earthquakes and add new scenarios to their models and improve impact forecasting. land.
The ocean floor seismic network was used as part of the PI-LAB and EUROLAB projects, a multimillion dollar experiment run by the Natural Environment Research Council in the UK, Chau Research Council. Funded by Europe and the National Science Foundation in the US.
Reference: “Back-propagation ultrasonic rupture in M 2016w 7.1 Romanche Variable Fault Earthquake ”by Stephen P. Hicks, Ryo Okuwaki, Andreas Steinberg, Catherine A. Rychert, Nicholas Harmon, Rachel E. Abercrombie, Petros Bogiatzis, David Schlaphorst, Jiri Zahradnik, J-Michael Kendall, Yuji Yagi, Kousuke Shimizu and Henriette Sudhaus, August 10, 2020, Natural geoscience.
DOI: 10.1038 / s41561-020-0619-9