Earthquakes
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Magnitude 6.9 earthquake strikes near Neiafu, Tonga

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An earthquake of magnitude 6.9 struck the Neiafu region in Tonga on Sunday, the United States Geological Survey said.

There was no tsunami danger for the US West Coast, British Columbia and Alaska, The US Tsunami Warning System said.

The quake was at a depth of 247 km (153.48 miles), the USGS said.

By Reuters

Attention

Strong earthquake swarm at Katla volcano in Iceland - 58 quakes and counting

katla volcano
© Icelandic Met OfficeOngoing earthquake activity in Katla volcano.
During the night of 30. June 2023 an earthquake swarm started in Katla volcano. At the writing of this article the largest verified earthquake had a magnitude of Mw3,3.

This earthquake swarm is ongoing at the writing of this article. Currently an eruption has not started, if that is going to change is something that just has to show it self in next few hours if this earthquake activity continues to increase. All that can be done for now is to monitor this situation.

Comment: One reader writes:
The swarm is situated in a fairly unusual spot, compared to earlier unrest. We have been used to seeing EQ activity closer to the northern rim of the caldera (closer to AUS station), not often in the center of it. This could evolve into a new, interesting chapter for Katla.
More interesting details from youtuber Oppenheimer Ranch:

See also: 'One day it will just go off': are Naples' volcanic craters at Campi Flegrei about to blow?


Info

The mysterious case of Ireland's missing earthquakes

The Emerald Isle has far fewer earthquakes than neighboring Britain. Now scientists think they know why.
Ireland and Britain
© NASAIreland and Britain sit thousands of kilometers from the nearest tectonic plate boundary and just a few dozen from each other, yet Britain experiences far more earthquakes than Ireland.
Ireland and Britain should be, seismologically speaking, equally boring. The two islands lie thousands of kilometers from the nearest plate boundary and are not volcanic hot spots. But though the ground rarely rumbles in Ireland, neighboring Britain experiences plenty of weak and moderate earthquakes.

The lithosphere — Earth's outermost rocky veneer, which includes the crust and the solid upper mantle — is thicker and cooler beneath Ireland than it is beneath Britain, new research has suggested. Cool, thick lithosphere is mechanically stronger than warm, thin lithosphere, which could explain the Emerald Isle's puzzling paucity of earthquakes. The new results, published in Geophysical Journal International, hinted that lithosphere thickness could underpin patterns in seismic activity in other places far from plate boundaries.

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Shallow 6.0-magnitude quake hits south of Tonga: USGS

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An earthquake with a magnitude of 6.0 jolted south of Tonga at 07:16:59 GMT on Sunday, the U.S. Geological Survey said.

The epicenter, with a depth of 7.087 km, was initially determined to be at 24.0318 degrees south latitude and 175.6262 degrees west longitude.

Question

Do cosmic rays cause earthquakes?

Cosmic Rays & Earthquakes
© PITRIS/GETTYA stock photo shows a concept of cosmic radiation. Scientists have found a link between cosmic radiation and earthquakes.
I came across an article with a provocative headline, "Scientists Link Cosmic Radiation to Earthquakes for the First Time".

So I went to look at the underlying study, Observation of large scale precursor correlations between cosmic rays and earthquakes with a periodicity similar to the solar cycle by P. Homola and 43 others.

Hmmm, sez I. Willis's Rule of Authors says that the strength of a scientific study is inversely proportional to the number of authors ... but I digress. The Abstract says:
The search for correlations between secondary cosmic ray detection rates and seismic effects has long been a subject of investigation motivated by the hope of identifying a new precursor type that could feed a global early warning system against earthquakes.

Here we show for the first time that the average variation of the cosmic ray detection rates correlates with the global seismic activity to be observed with a time lag of approximately two weeks, and that the significance of the effect varies with a periodicity resembling the undecenal solar cycle, with a shift in phase of around three years, exceeding 6 σ at local maxima.

The precursor characteristics of the observed correlations point to a pioneer perspective of an early warning system against earthquakes.
The study says:
Here we report on an observation of the correlations between variation of the average rates of secondary cosmic ray fluxes measured locally and global seismic activity, and we also point to the periodicity of these correlations (or their observability) which corresponds to sunspot number observations back to the 1960s.
They describe their method as:
... an alternative, novel approach on which we report here: comparing the absolute average variabilities of secondary cosmic radiation to the average global sum of earthquake magnitudes.
And their conclusion was:
We have demonstrated for the first time that the variation of the absolute average detection rates of secondary cosmic radiation correlates with the global seismic situation (sum of the magnitudes of earthquakes with magnitudes greater-than or equal to 4, occurring at all locations) that takes place approximately two weeks later than the relevant cosmic ray data. The size of the shift in time between the cosmic and seismic data sets reveals the precursor character of the correlation effect.

Seismograph

Shallow 6.0 magnitude earthquake off South Africa

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6.0 magnitude earthquake

UTC time: Sunday, June 18, 2023 21:59 PM
Your time: Sunday, June 18, 2023 at 10:59 PM GMT+1
Magnitude Type: mww
USGS page: M 6.0 - south of Africa
USGS status: Reviewed by a seismologist
Reports from the public: 0 people
10 km depth
South Of Africa

Seismograph

Shallow 6.4 magnitude earthquake hits Gulf of California

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An earthquake of magnitude 6.4 struck the Gulf of California on Sunday, the European Mediterranean Seismological Centre (EMSC) said.

Mexico's civil defense office confirmed that there were no immediate reports of damage in the areas where the earthquake was felt, but recommended boats and the nearby coastal population take precautions due to possible currents in ports.

The quake struck at a depth of 10 km (6.21 miles), EMSC said.

Shortly after the quake occurred, the US Tsunami Warning system said there was no tsunami danger for the US West Coast, British Columbia, or Alaska.

Small variations in sea water levels, of a few centimeters, may be detected in the region where the quake occurred, the Mexican civil defense office later said via Twitter.

Seismograph

Best of the Web: France hit by one of its strongest ever earthquakes

Seismograph
© Thinkstock
A rare and powerful earthquake with a magnitude of 5.8 hit several parts of western France on Friday evening. The earthquake was described as "very strong" by the seismology bureau BCSF, and it resulted in damage to buildings.

According to the ecology transition minister, Christophe Bechu, it was one of the strongest quakes ever recorded on the mainland.

The last earthquakes of similar strength in France occurred in the early 2000s, making this event significant. The earthquake was recorded at 5.3 by the national network for seismic surveillance, RENASS, while the French Central Seismological Bureau (BCSF) reported it at 5.8.

Comment: To be clear, the strongest EVER recorded quake in (modern) France was a 6.2M, in 1909.




Seismograph

6.2 magnitude earthquake south of Tonga - 3rd major quake in area in 25 hours

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6.2 magnitude earthquake 259 km from 'Ohonua, ʻEua, Tonga

UTC time: Friday, June 16, 2023 19:10 PM
Your time: Friday, June 16, 2023 at 8:10 PM GMT+1
Magnitude Type: mww
USGS page: M 6.2 - 251 km SSW of 'Ohonua, Tonga
USGS status: Reviewed by a seismologist
Reports from the public: 0 people

Comment: The two others:


Seismograph

Magnitude 6 earthquake strikes Tonga region - 2nd major quake in area in 14 hours

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An earthquake of magnitude 6 struck the Tonga region on Friday, the European Mediterranean Seismological Centre (EMSC) said.

The quake was at a depth of 100 km (62 miles), EMSC said.

Comment: 14 hours earlier: 7.2-magnitude earthquake hits Pacific south of Tonga