Apr 22, 2020 05:25 AM
(This post was last modified: Apr 22, 2020 06:18 PM by C C.)
Australia’s rivers will be unrecognisable by 2070
https://theconversation.com/australias-i...ble-136492
EXCERPT: Inland Australia's complex system of winding rivers, extensive wetlands, ancient waterholes and seemingly endless parched floodplains are rarely given more than a passing thought by many Australians who live on the coastal fringes.
Yet these waterways are lifelines along which communities, agriculture and trade have flourished. [...] these rivers evolved over millennia and continue to change over years and decades. And we already know from previous studies that future climate change is likely to reduce stream flow and water availability in drylands around the world.
But what our new research has shown, for the first time, is that these declines in stream flow may trigger a dramatic change in the physical structure and function (the geomorphology) of Australia’s inland rivers... (MORE - details)
New Earthquake Math Predicts How Destructive They’ll Be
https://www.quantamagazine.org/new-earth...-20200421/
EXCERPT: . . . When a fault slips, it unleashes a torrent of seismic waves, not all of them alike. Long low-frequency waves can travel far from their source and cause tall structures like skyscrapers to sway, while high-frequency waves are excellent at shaking houses and bridges and reducing them to rubble. For much of the past half-century, seismologists have assumed that the frictional slippage of a fault generates this entire seismic suite.
Now a pair of geoscientists from Brown University have conjured up their own origin story. Using mathematical models inspired by landslides and avalanches, the researchers argue that these damaging high-frequency waves are caused not by the slippage itself, but by geological pinball games taking place within the fault.
“What they’ve done here is pretty neat,” said Elizabeth Cochran, a seismologist at the U.S. Geological Survey. “I certainly wouldn’t have thought to represent a fault in the way that they have.” The new model, published last month in Geophysical Research Letters, still needs to be tested on future quakes, to see if it accurately predicts their properties. But if corroborated, it would upend our understanding of earthquakes’ capacity for destruction and perhaps save lives in the process.
[...] This new model could help solve some long-standing seismological riddles. ... The new model may also explain why earthquakes on mature faults — older ones that have slipped many times — tend to generate less damage than earthquakes of equal magnitude on immature faults. The former, with a long history of temblors, have repeatedly ground down their internal debris, allowing for fewer collisions and producing weaker high-frequency waves.If the model is validated, said Graves, it suggests that scientists can carefully study a fault zone and use its geometry to forecast what the damaging high-frequency wave component of a future earthquake may be... (MORE - details)
https://theconversation.com/australias-i...ble-136492
EXCERPT: Inland Australia's complex system of winding rivers, extensive wetlands, ancient waterholes and seemingly endless parched floodplains are rarely given more than a passing thought by many Australians who live on the coastal fringes.
Yet these waterways are lifelines along which communities, agriculture and trade have flourished. [...] these rivers evolved over millennia and continue to change over years and decades. And we already know from previous studies that future climate change is likely to reduce stream flow and water availability in drylands around the world.
But what our new research has shown, for the first time, is that these declines in stream flow may trigger a dramatic change in the physical structure and function (the geomorphology) of Australia’s inland rivers... (MORE - details)
New Earthquake Math Predicts How Destructive They’ll Be
https://www.quantamagazine.org/new-earth...-20200421/
EXCERPT: . . . When a fault slips, it unleashes a torrent of seismic waves, not all of them alike. Long low-frequency waves can travel far from their source and cause tall structures like skyscrapers to sway, while high-frequency waves are excellent at shaking houses and bridges and reducing them to rubble. For much of the past half-century, seismologists have assumed that the frictional slippage of a fault generates this entire seismic suite.
Now a pair of geoscientists from Brown University have conjured up their own origin story. Using mathematical models inspired by landslides and avalanches, the researchers argue that these damaging high-frequency waves are caused not by the slippage itself, but by geological pinball games taking place within the fault.
“What they’ve done here is pretty neat,” said Elizabeth Cochran, a seismologist at the U.S. Geological Survey. “I certainly wouldn’t have thought to represent a fault in the way that they have.” The new model, published last month in Geophysical Research Letters, still needs to be tested on future quakes, to see if it accurately predicts their properties. But if corroborated, it would upend our understanding of earthquakes’ capacity for destruction and perhaps save lives in the process.
[...] This new model could help solve some long-standing seismological riddles. ... The new model may also explain why earthquakes on mature faults — older ones that have slipped many times — tend to generate less damage than earthquakes of equal magnitude on immature faults. The former, with a long history of temblors, have repeatedly ground down their internal debris, allowing for fewer collisions and producing weaker high-frequency waves.If the model is validated, said Graves, it suggests that scientists can carefully study a fault zone and use its geometry to forecast what the damaging high-frequency wave component of a future earthquake may be... (MORE - details)