Since then giant earthquakes have been thought to be possible on any large fault. In the new paper UO researchers show that the maximum size of earthquakes may be controlled by another parameter: the fault curvature. The way people in the science community think about earthquakes is that some fault areas resist failure more than others, and when they break they generate large earthquakes, said lead author Quentin Bletery, a postdoctoral researcher at the UO. What I found is the opposite of what I expected: Very large earthquakes occur on fault areas where the slope is the most regular, or flat.
The rupture threshold is more homogeneous along flat faults, allowing larger fault areas to rupture simultaneously, the researchers said. Based on the average curvature inside the giant earthquake rupture areas, the researchers concluded that the likelihood that mega-earthquakes are linked to fault curvatures is more than 99 percent.
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The erosion rates of cliffs along the Sussex coast have rapidly sped up in the last 200 years, a new study has found. The research shows that the erosion rates along Beachy Head and Seaford Head in Sussex had remained relatively stable, at around two to six centimetres each year, for thousands of years. Cliff erosion is irreversible; once the cliffs retreat, they are gone for good.
This isotope is created when cosmic radiation reacts with oxygen atoms in the exposed flint rock, so by measuring its accumulation, it acts as a kind of rock clock to show the rate of rock erosion. Since the rate of accumulation has previously been relatively constant, measuring rock samples from across the shore platforms allowed researchers to build a record of how coastal erosion has proceeded over the last 7000 years or so. New fossils discovered in East Greenland record an empty alien world from immediately after the extinction, which marked what is formally known as the Permian-Triassic boundary. Our discovery is significant because it shows for the first time that sea floor life at higher latitudes suffered the same global extinction process, and subsequent ecosystem recovery, says Dr Benjamin Kear from the Museum of Evolution at Uppsala University and leader of the project funded by the Swedish Polar Research Secretariat.
Palaeontologists from Uppsala University spent more than two months collecting fossils in East Greenland. East Greenland is the only landmass where rocks of these ages occur together in the same place, says Dr Henning Blom of the Evolutionary Biology Centre at Uppsala University, and co-investigator on the Swedish Polar Research Secretariat project. Some Los Angeles earthquakes possibly triggered by oil production in early 20th century 1/3/1611/2/2016 If you take our four-the 1920, 1929, 1930 and 1933 earthquakes-out of the calculations as induced or potentially induced, it does call into question what the rate of natural earthquakes in the L.A. Basin really is, Hough suggests. Los Angeles oil boom began in 1892 when oil was discovered near present-day Dodger Stadium, and L.A. Basin oil fields accounted for nearly 20 percent of the worlds total production of crude oil by 1923. Houghs earlier studies of historic induced earthquakes in Oklahoma gave her the idea to look for oil permits and other industry records online, and she eventually found a site containing state reports that summarized the operations of California oil fields in the early 20th century. By comparing the earthquake lists with the industry data, the researchers found several links between earthquakes and significant oil production activities that took place nearby and close to the same time as the quakes. The recent increase in human-caused earthquakes in the central United States and Canada make it important to understand the full context of how, where and why earthquakes are induced, Hough notes. |
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February 2017
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