Thursday , September 24 2020

Earthquakes with the lowest zones indicate how small faults can cause large earthquakes


When an earthquake strikes, many Californians need to ask themselves the question: Which fault is faulty – Portport-Inglewood, Hayward, the mighty San Andreas?

But scientists are increasingly saying it's not that simple.

New research shows that the Rijerkest earthquakes, which began in July, have broken at least twenty errors. It is the latest evidence of how small bugs can come together to cause a major earthquake and how those earthquakes can cover a wider area than expected.

The findings are important to understand how earthquakes can grow in seconds after a breakdown occurs when two blocks of land are separated from each other. In areas covered by a faulty spraying scheme, a minor sin earthquake can destabilize the larger, initiating a process leading to a much stronger earthquake.

In the case of Rijskest, some subsequent earthquakes occurred a few seconds later; the largest came about 34 hours later.

Only in recent decades have earthquake scientists understood how smaller bugs in California came together to create a more powerful earthquake.

After the 1992 Landers earthquake, scientists were amazed to discover that the 7.3-degree tempera- ture in the Mojave Desert had broken down into five separate bugs.

As the years went by, more evidence was accumulating that earthquakes could and do occur more frequently – such as a 7.1 hectare earthquake, about 20 miles east of the Landers earthquake and a 7.2 magnitude earthquake in Easter. Sunday 2010 near Mexico.

The detailed findings, recently published in Science journal by Caltech experts and NASA's aircraft engineer laboratory, highlight how scientists' understanding of earthquake disruptions has evolved.

The researchers found that the July 4th Rijskest temperature was actually three different earthquakes – magnitudes 6.1, 6.2 and 6.2 – of three errors. Together, they produced enough energy to create a 6.4-degree temblor, said Zahari Ross, an assistant professor of geophysics at Caltech, the lead author of the paper. The first two earthquakes broke at right angles to each other, forming the capital letter L: the first to the northwest and southeast, the second to the southwest. The third earthquake also collapsed in the south-west. The errors were corrupted for over 12 seconds.

"This is something we haven't seen before, and it's been detailed in great detail to such an extent," said seismologist Caltech, Egil Faucson, co-author and expert on seismology in Southern California.

The second major earthquake, on July 5, actually consisted of four smaller events that broke down in 22 seconds, creating a magnitude of 7.1, the most powerful in California in 20 years. In that case, at least 20 minor faults that cut off the major faults were also corrupted, according to the study, making the area of ​​land at the top of the removable faults wider than expected.


The animation does not reflect the actual speed.

(Saint Canaan / The Los Angeles Times)

"The geometry of this fault network is incredibly complicated," Ross said. "These mistakes are unexplored … many of them are at right angles to each other; they intersect. In the central part of it, they are located a few kilometers away, like a domino. There are 20 of them in a row. This 7.1 scattered all this. "

The results provide further evidence to support the idea that California faults, which were thought to be limited by their individual length, could in fact be linked to a much larger earthquake.

For example, as stated in a 1993 study in the journal Science coautorored by Hauksson, previous estimates suggested that only 6.9 magnitude earthquakes or less would be expected in the Landers area. A 7.3 magnitude earthquake in which a quarter appeared to stifle the shaking energy of what was expected.

"The point is that the Landers earthquake and this earthquake are faults that fix the faults that were previously thought to be collapsing on their own, and that's an important exaggeration," Hawkson said. "These earthquakes linked segments that were previously thought to be independent, but have now turned out to be connected in one major earthquake."

So, instead of being released by the earthquake virus from very large nebulae with many faults, "you can only do this in one size 7 by making the journey last and jumping from one fault to another," Hawkson said.

A modest error that begins to move in the earthquake can ease the rupture of the neighboring fault, said Hawkson. In Rigestres, the July 4th earthquakes were probably held in hammers with strong spots amid seismic-stricken faults until the larger magnitude 7.1 broke on July 5, Hawksson said.

The study raises the possibility that earthquakes in the past may have been larger than previously thought. The prehistoric earthquake, currently identified by a breakdown in one place, could produce even more power if scientists had not yet discovered other segments of faults that had collapsed in the same event, the study said.

It may sound sinister. But it has a silver lining, according to seismologist Lucy onesons, who was not included in the study.

If endangered earthquakes are more likely, it means there will be less harmful sacks during a given time period. "You won't have to have another earthquake in a while," Ons said.

"What's worse, one 8 or six 7.5?" Asked Jones. "It's not clear that one 8 is worse than six 7.5. There's a lot of damage that happens in every single event. "

And on a large scale, there is only so much land that can be shaken before the rocks break; so the worst quake caused by an earthquake of magnitude 7 and magnitude 8 is not that different. The 8-magnitude earthquake will, however, bring destructive shake to a much larger area of ​​California and its duration will be longer.

The Ridgecrest study and information from other recent earthquakes have also highlighted the importance of understanding how multiple bugs can affect a wider area.

In New Zealand, scientists were amazed at the bizarre map of the 7.8-magnitude earthquake-ridden faults in 2016, reminiscent of an inverted triad aimed at the eagle's silhouette.

Earthquake Kaikura

Map showing where the faults on the surface of the 7.8 magnitude earthquake ruptured according to Kaikura in New Zealand in 2016.

(GNS Science)

"In the Kaikura earthquake, there were more cracks across a wide area … and that is alert thinking," Hawkson said. "And it's important because it means a lot more people are affected – surface decomposition and surface shaking are spreading to a much wider area."

At the practical level, the research highlights the potential limitations of state-owned earthquake zones designated to prevent new construction directly from errors, said Hawkson. If one major mistake can be overcome with much shorter normal errors and officials want to avoid new builds of active errors, the zones may have to be larger than they are now, he said.

Further analysis needs to be done to determine if the 20 crossover errors identified in the Ridgecrest study by computer analysis of shaking records actually crashed to the surface, according to Tim Dawson, a senior engineering geologist with a geological survey in California.

The Rijksest earthquakes have occurred in a region already known to be deeply complex, with many structurally immature, cross-linked child faults, said USC Agriculture Professor James Dolan.

"It's simple, it's very interesting to see that one of these errors is mixed at the same time in a big earthquake," Dolan said.

A significant achievement of this study, Dolan said, was being able to imagine what bugs look deep underground at the depths from where the earthquakes begin. The old conventional wisdom was that the structurally complex nature of surface errors becomes simpler as you go deeper; what this study proves is that the structural complexity continues deep underground where earthquakes begin, Dolan said.

That's important, Dolan said, because it can help scientists determine where future earthquakes are likely to stop, which tends to occur when the errors become structurally complicated.

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