Jun 8, 2022 07:33 PM
Lab earthquakes show how grains at fault boundaries lead to major quakes
https://www.eurekalert.org/news-releases/955258
INTRO: By simulating earthquakes in a lab, Caltech engineers have provided strong experimental support for a form of earthquake propagation now thought responsible for the magnitude-9.0 earthquake that devastated the coast of Japan in 2011.
Along some fault lines, which are the boundaries of tectonic plates, a fine-grained gravel is formed as the plates grind against one another. The influence of this gravel on earthquakes has long been the subject of scientific speculation. In a new paper appearing in the journal Nature on June 1, the Caltech researchers show that the fine gravel, known as rock gouge, first halts earthquake propagation, but then triggers the rebirth of earthquakes to generate powerful ruptures.
"Our novel experimental approach has enabled us to look into the earthquake process up close, and to uncover key features of rupture propagation and friction evolution in rock gouge," says Vito Rubino, research scientist and lead author of the Nature paper. "One of the main findings of our study is that fault sections previously thought to act as barriers against dynamic rupture may in fact host earthquakes, as a result of the activation of co-seismic friction weakening mechanisms." (MORE - details)
New research suggests Earth's magnetic polarity isn't reversing
https://www.upi.com/Science_News/2022/06...654702819/
RELEASE: A South Atlantic rapid geomagnetic field decrease known as the South Atlantic Anomaly led to speculation that Earth's magnetic polarity was reversing. But a new study, published this week in the journal PNAS, suggests the reversal may not be happening after all.
"We have mapped changes in the Earth's magnetic field over the past 9,000 years, and anomalies like the one in the South Atlantic are probably recurring phenomena linked to corresponding variations in the strength of the Earth's magnetic field," lead study author Andreas Nilsson, a geologist at Lund University in Sweden, said in a press release.
Nilsson said that, based on the new modeling, researchers have concluded that Earth is not heading toward a polarity reversal.
Earth's magnetic field is not stable, and polarity reversals where the North and South poles flip has happened on average roughly every 200,000 years.
During the past 180 years, Earth's magnetic field strength has declined by about 10%. The magnetic field protects Earth's atmosphere from being swept away by solar winds.
The results reported in the new study are based on analyzing archaeological artifacts, volcanic samples and sediment drill cores. According to Nilsson, a new modeling technique that combines data from those samples created one global reconstruction of the magnetic field over 9,000 years, and that led to the conclusion that magnetic polarity is not reversing.
https://www.eurekalert.org/news-releases/955258
INTRO: By simulating earthquakes in a lab, Caltech engineers have provided strong experimental support for a form of earthquake propagation now thought responsible for the magnitude-9.0 earthquake that devastated the coast of Japan in 2011.
Along some fault lines, which are the boundaries of tectonic plates, a fine-grained gravel is formed as the plates grind against one another. The influence of this gravel on earthquakes has long been the subject of scientific speculation. In a new paper appearing in the journal Nature on June 1, the Caltech researchers show that the fine gravel, known as rock gouge, first halts earthquake propagation, but then triggers the rebirth of earthquakes to generate powerful ruptures.
"Our novel experimental approach has enabled us to look into the earthquake process up close, and to uncover key features of rupture propagation and friction evolution in rock gouge," says Vito Rubino, research scientist and lead author of the Nature paper. "One of the main findings of our study is that fault sections previously thought to act as barriers against dynamic rupture may in fact host earthquakes, as a result of the activation of co-seismic friction weakening mechanisms." (MORE - details)
New research suggests Earth's magnetic polarity isn't reversing
https://www.upi.com/Science_News/2022/06...654702819/
RELEASE: A South Atlantic rapid geomagnetic field decrease known as the South Atlantic Anomaly led to speculation that Earth's magnetic polarity was reversing. But a new study, published this week in the journal PNAS, suggests the reversal may not be happening after all.
"We have mapped changes in the Earth's magnetic field over the past 9,000 years, and anomalies like the one in the South Atlantic are probably recurring phenomena linked to corresponding variations in the strength of the Earth's magnetic field," lead study author Andreas Nilsson, a geologist at Lund University in Sweden, said in a press release.
Nilsson said that, based on the new modeling, researchers have concluded that Earth is not heading toward a polarity reversal.
Earth's magnetic field is not stable, and polarity reversals where the North and South poles flip has happened on average roughly every 200,000 years.
During the past 180 years, Earth's magnetic field strength has declined by about 10%. The magnetic field protects Earth's atmosphere from being swept away by solar winds.
The results reported in the new study are based on analyzing archaeological artifacts, volcanic samples and sediment drill cores. According to Nilsson, a new modeling technique that combines data from those samples created one global reconstruction of the magnetic field over 9,000 years, and that led to the conclusion that magnetic polarity is not reversing.