Aardbevingen #19

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Op woensdag 8 november 2017 22:12 schreef -CRASH- het volgende:
17:40 Lichte aardbeving (magnitude 3.o) op 10 km diepte
,en 24 km ten zuid-westen van Keulen.

[ afbeelding ]

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Op dinsdag 7 november 2017 18:52 schreef Frutsel het volgende:

[..]

Hoe ongewoon is dat voor Noorse begrippen?

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More big earthquakes in 2018 as Earth slows slightly, theory suggests

Two US scientists have come up with a theory that suggests a big increase in devastating earthquakes, particularly near the Equator, in 2018 following a tiny slowing in the Earth's rotation.

"The correlation between Earth's rotation and earthquake activity is strong and suggests there is going to be an increase in numbers of intense earthquakes next year," Roger Bilham of the University of Colorado told The Observer.

Bilham and Rebecca Bendick of the University of Montana presented a paper on the link between seismic activity and the Earth's rotation speed at the annual meeting of the Geological Society of America.

The slowdown in Earth's rotation is tiny - a millisecond a day sometimes - which can be measured by atomic clocks.

Bilham and Bendick found that periods when the number of intense earthquakes had increased followed periods of about five years when the Earth's rotation slowed slightly.

Earth's rotation began one of the periodic slowdowns more than four years ago.

"Next year we should see a significant increase in numbers of severe earthquakes," Bilham said. "We have had it easy this year. So far we have only had about six severe earthquakes. We could easily have 20 a year starting in 2018."

The link between the Earth's rotation and the number of big earthquakes was unclear, but slight changes in the behaviour of the Earth's core could be causing both effects.

Most of the intense earthquakes that responded to changes in day length seemed to occur near the Equator, Bilham said.

Bilham and Bendick looked at earthquakes of magnitude 7 and greater since 1900, finding five periods when the number of big quakes increased significantly.

In those periods there were 25-30 intense quakes a year, compared to an average of about 15 at other times.

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Op maandag 25 december 2017 16:31 schreef Frutsel het volgende:

[..]

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Op donderdag 4 januari 2018 12:38 schreef Frutsel het volgende:
Ooit wel

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Tectonic Summary

The January 10, 2018, M 7.6 Great Swan Island, Honduras earthquake occurred as the result of strike slip faulting in the shallow crust near the boundary between the North America and Caribbean plates. Early focal mechanism solutions indicate that rupture occurred on a steeply dipping structure striking either west-northwest (right-lateral), or west-southwest (left-lateral). At the location of this earthquake, the North America plate moves to the west-southwest with respect to the Caribbean plate at a rate of approximately 19 mm/yr. Local to the January 10, 2018 earthquake, this motion is predominantly accommodated along the Swan Islands transform fault, a left-lateral structure. The location, depth and focal mechanism solution of today's earthquake are consistent with rupture occurring along this plate boundary structure, or on a nearby and closely related fault.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Strike-slip-faulting events of the size of the January 10, 2018, earthquake are typically about 140x20 km (length x width).

Nine other earthquakes of M 6 or larger have occurred within 400 km of the January 10, 2018 event over the preceding century. Previous strong earthquakes along the North America-Caribbean plate boundary in this region include the destructive M 7.5 Guatemala earthquake of February 4, 1976, which resulted in more than 23,000 fatalities. The 1976 earthquake occurred on the Motagua fault, a segment of the plate boundary that lies in southern Guatemala, about 650 km west-southwest of the hypocenter of the January 10, 2018, event. In May 2009, a M 7.3 earthquake occurred along the Swan Island transform fault approximately 300 km west of the January 10, 2018 event. The 2009 earthquake (which was much closer to land than the 2018 event) resulted in 7 fatalities, 40 injuries and 130 buildings being damaged or destroyed.

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An earthquake of magnitude 7.6 that struck in the Caribbean sea on Tuesday was felt across northern Central America, briefly prompting a tsunami warning for disaster-hit Puerto Rico and the British and US Virgin Islands.

The US Tsunami Center later cancelled the alert but warned some parts of Honduras and Belize were still at risk from waves of up to a metre.

The quake - which hit at 10.52pm local time - rattled windows in the Honduran capital of Tegucigalpa roughly 323 miles (519km) to the east and was felt at least as far north as the Mexican state of Quintana Roo, but no damage was immediately reported.

Rodrigo Anaya Rodriguez was in a hammock inside his house near popular tourist site Bacalar Lake on Mexico's Caribbean coast in Quintana Roo when he felt three tremors. "It felt like a bulldozer was driving past," he said. "It didn't last long but was very violent." He ran to his balcony and saw electricity posts and cables swaying.

In Honduras, firefighters said some residents in southern neighborhoods fled their homes after feeling the tremors. "We have reports that it was felt in the majority of the country, but we don't have reports of damage," said Lizandro Rosales, director of Honduras' contingencies commission.

The US Geological Survey said the quake, initially reported as a magnitude 7.8, was centered 125 miles (202km) north-east of Barra Patuca in Honduras and 191 miles (307km) south-west of George Town in the Cayman Islands.

The quake was very shallow, at only 6.2 miles (10km), which would have amplified its effect. It was lightly felt in Belize's capital, Belize City, but did not prompt immediate reports of damage.

Belize's minister in charge of emergency management, Edmond Castro, spoke on local radio to urge people living in low lying coastal areas and islands to stay alert for potentially dangerous waves.