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Mon, 27 Sep 2021
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Earthquakes

Seismograph

Earthquake swarm shakes Oregon's Mount Hood

Mount Hood earthquake swarm
© Pacific Northwest Seismic Network
Two earthquakes hit Saturday near Government Camp, Oregon, one of them topping out at magnitude 3.9.

The tremors were strong enough for some locals to feel it, The Oregonian reported.

The earthquake rumbled at 8:51 p.m. June 5, just south of the summit of Mount Hood. It was preceded by several earthquakes in the hour before the quake, and tens of aftershocks have occurred since, the Cascades Volcano Observatory of the U.S. Geological Survey reported in a news release Saturday night.

The volcanic action and location are consistent with past swarms in the Mount Hood area, including a magnitude 4.5 on June 29, 2002, that was located about 1 mile east of Saturday's ground shaker.

Aftershocks will likely continue for hours or days, some of which may be felt, according to the news release.

Comment: A few days ago a significant earthquake swarm hit southern California.


Seismograph

Significant earthquake swarm impacting southern California

A swarm of earthquakes is currently impacting southern California
© USGS
A swarm of earthquakes is currently impacting southern California
A significant earthquake swarm is unfolding in southern California, impacting the area around the Salton Sea east of San Diego, south of Palm Springs, and southeast of Los Angeles. 47 earthquakes with a magnitude of 2.5 or greater have struck the area, with the strongest being a 5.3 which struck at 10:55am local time today.

The strong 5.3 earthquake struck about 6 and a half miles west of Calipatria at a depth of 3.6 miles. More than 700 residents from Los Angeles to San Diego to El Centro reported experiencing the quake to the USGS, including many that reported "strong shaking."

Today's significant earthquake swarm is occurring near the Salton Sea, a shallow landlocked lake with a high salt concentration in Riverside and Imperial counties of California. The Salton Sea sits on the San Andreas Fault at the southern end of the state of California. In this region, the Earth's crust is being stretched. Today's earthquakes are tied to submerged faults near the southern end of the San Andreas Fault. Called the Brawley seismic zone, this extensional region connects the San Andreas with the Imperial Fault in southern California.

Today's swarm comes on the heels of another earthquake swarm that impacted the Disney Land area last weekend north of today's swarm.

Seismograph

No tsunami warnings after two 5.9 magnitude earthquakes hit off Oregon coast

A cluster of earthquakes were reported in the same area at the end of April.

A cluster of earthquakes were reported in the same area at the end of April.
Two 5.9 magnitude earthquakes struck the Pacific Ocean off Oregon's coast early Friday morning, the United States Geological Survey (USGS) reported.

The tremors occurred about 89 miles and 98 miles west of the coastal town of Gold Beach, Oregon, after 1 a.m. (PT) Friday morning, according to USGS.

A few people reported light shaking on the coast, the USGS report showed.

At least five earthquakes ranging in magnitudes from 3.2 to 5.9 have occurred in the area in the last few hours, according to USGS.

Seismograph

6.1 magnitude earthquake hits eastern Indonesia

graph
A 6.1-magnitude earthquake struck off the coast of Indonesia's remote Maluku islands Thursday, the United States Geological Survey said, but no tsunami warning was issued.

The strong quake hit at a relatively shallow depth of 31 kilometres (20 miles), about 127 kilometres southwest of the city of Ternate.

Shallower quakes tend to cause more damage, but there were no immediate reports of casualties.

"It was a decent shake, but people weren't panicking," said Ternate resident Nasarudin Amin.

"There are warnings about potential aftershocks."

Seismograph

Small earthquake, loud boom rattles part of New York state

Seismograph
© WPDH
Earthquakes in New York? Yes, it does happen occasionally. If you have friends or relatives in Livingston County, then you might want to check to see if they felt the small tremor that occurred Thursday evening. The United State Geological Survey says the small 2.4 magnitude quake struck just north of the town of Tuscarora, NY, just east of Letchworth State Park. WBNG did not indicate whether or not there was any damage in the area.

But while the quake was small, it was also considered shallow (around 12,000 feet below the surface, according to WROC) The Daily News Online says that some residents described the tremor on social media as a "loud boom", while others said their porch floor shook "quickly and vigorously". Livingston County Sheriff Thomas Dougherty said over Twitter that his office received multiple calls from concerned residents.

Back in March, an area just north of the Hudson Valley felt an earthquake, somewhat like this most recent tremor The United States Geological Survey says a small quake occurred near Altamount, NY, in Albany County. News 10 is reporting that the quake measured a 2.0 on the Richter Scale. Yes, earthquakes do happen in the Northeastern U.S. and Canada. 2020 actually started off with three small earthquakes, on January 3, 7, and 13 respectively. The third was the strongest of the trio, measuring a magnitude 3.3, that hit several miles south of the town of Ormstown, Quebec. The Times Union says the quake was felt as far south as the town of Ticonderoga, NY.

Seismograph

6.1 earthquake shakes Southcentral Alaska

graph
An earthquake with a magnitude of 6.1 centered under the Talkeetna Mountains in the Matanuska-Susitna Borough shook Southcentral Alaska on Sunday evening.

The quake hit just before 11 p.m. and was centered about 60 miles east of Talkeetna and around 100 miles northeast of Anchorage, according to the Alaska Earthquake Center. It was centered at a depth of about 27 miles. the center reported.

The USGS initially reported the preliminary magnitude as 6.0 and later adjusted the magnitude to 6.1 after review.

The earthquake was felt from Homer to Fairbanks, and was felt especially strongly the Mat-Su and Anchorage areas. ADN readers on Facebook described items falling off shelves, and many described rolling motion.

Bizarro Earth

Water causes the deep Earth's most mysterious earthquakes says research

Deep Earthquakes
© Illustration by Steven Shirey, Peter van Keken, Lara Wagner, and Michael Walter/Carnegie Institution for Science.
Some of Earth's largest earthquakes occur at tremendous depths (500-700 km) beneath the surface, always within or near oceanic plates that have sunk back into the Earth's interior. The cause of these events has been an enduring question in geology and geophysics for more than 40 years. In a new paper, a team of Carnegie and University of Alberta geoscientists provide several lines of evidence that fluids contribute to the genesis of deep earthquakes. New thermal modeling shows that carbonated crust and hydrated mantle in cold slabs can transport these fluids down to where deep earthquakes occur. Evidence from diamonds provides mineralogical proof of these mobile fluids in the mantle transition zone (440 - 670 km depth). This figure shows a sample thermal model of a subduction zone, with the relatively cold (blue) oceanic plate sinking into the comparatively hot (red) mantle. Three regions of earthquakes (grey spheres) visible in the oceanic plate: "intermediate-depth" dehydration-related earthquakes occurring between ~70 and ~250 km, a region of reduced seismicity between ~250 and ~350 km, and the region of "deep" seismicity below 350 km that extends to ~700 km. Superdeep diamonds (blue octahedra) are known to crystallize from fluids released in this deep region as the oceanic plate warms by the heat from the surrounding mantle.
Washington, DC — The cause of Earth's deepest earthquakes has been a mystery to science for more than a century, but a team of Carnegie scientists may have cracked the case.

New research published in AGU Advances provides evidence that fluids play a key role in deep-focus earthquakes — which occur between 300 and 700 kilometers below the planet's surface. The research team includes Carnegie scientists Steven Shirey, Lara Wagner, Peter van Keken, and Michael Walter, as well as the University of Alberta's Graham Pearson.

Most earthquakes occur close to the Earth's surface, down to about 70 kilometers. They happen when stress builds up at a fracture between two blocks of rock — known as a fault — causing them to suddenly slide past each other.

However, deeper into the Earth, the intense pressures create too much friction to allow this kind of sliding to occur and the high temperatures enhance the ability of rocks to deform to accommodate changing stresses. Though theoretically unexpected, scientists have been able to identify earthquakes that originate more than 300 kilometers below the surface since the 1920s.

"The big problem that seismologists have faced is how it's possible that we have these deep-focus earthquakes at all," said Wagner. "Once you get a few tens of kilometers down, it becomes incredibly difficult to explain how we are getting slip on a fault when the friction is so incredibly high."

Seismograph

M4.2 quake shakes Lake Tahoe, comes amidst uptick in activity in region

quake tahoe
A 4.2 magnitude earthquake has shaken the Lake Tahoe area Friday morning.

According to the US Geological Survey, the quake struck just before 8:30 a.m. and was centered about 5 miles southeast of the unincorporated community of Dollar Point.

This puts the epicenter of the quake right in the middle of Lake Tahoe.

Comment: On the 17th May CBS Sacramento reported that the increase in quakes appear to reflect the region being in an active period and that it may foreshadow larger quakes:
Frequent earthquakes across Northern California over the last several weeks have sparked questions about the natural disasters ahead.

State Geologist Steve Bohlen with California Geological Survey says the region has recently experienced earthquakes in rapid succession.

"We happen to be in a bit of an active period right now," said Bohlen.

At the end of April, a 3.8-magnitude earthquake hit the center of Lake Tahoe, followed by a 4.7-magnitude earthquake in Truckee, which was felt from Sacramento all the way to Reno.

"That was the biggest one I felt since I was out here. There were some lights and stuff swinging, something fell off the wall," said Ryan Callahan, who was at the Tourist Club in Truckee when the earthquake hit.

Seismologists tracking the activity say there's another, uncommon threat as well.

"There is a Tsunami hazard around Lake Tahoe," said Bohlen, who explains a magnitude-7 earthquake coming from the lake, though unlikely, could cause Tsunami-like waves.

"It would be significant emergency response effort in the Tahoe area if a magnitude-7 were to occur," he said.

How would you know if a Tsunami hit?

"If you feel an earthquake for [an] extended period of time, you really ought to think about moving to higher ground as quickly as possible," he said.

"It's an interesting idea thinking there could be a tsunami in Lake Tahoe," said Logan, who's visiting North Lake Tahoe this week.

But Tsunamis aren't something to sell your lakefront house over. Bohlen says just be prepared.

"Californians should have a safety kit with food, water...have a family plan of how to get together...when cellphones are down," he said.

An early warning system called Shake Alert could give precious extra seconds when an earthquake does hit.



Seismograph

Earthquakes in Congo raze buildings, stoke fear of second volcanic eruption

Lava from the eruption of Mount Nyiragongo
© AP
Lava from the eruption of Mount Nyiragongo cuts through Buhene north of Goma, Congo, May 24, 2021.
An earthquake on the border of Congo and Rwanda razed buildings in the city of Goma on Tuesday and stoked fears a nearby volcano would erupt again three days after dozens of people were killed and 17 villages were destroyed by lava.

The quake, measured at 5.3 magnitude by the Rwandan Seismic Monitor, was the largest of over 100 tremors that have followed the eruption on Saturday of Congo's Mount Nyiragongo volcano, one of the world's most active and dangerous.

"We know that children were injured when a building collapsed on Tuesday just a few steps from the UNICEF office in Goma," the U.N.children's agency said.

The quake appeared to have destroyed several buildings in the city of two million, and a witness said at least three people were pulled from the rubble and taken to hospital.

It struck at 11:03 a.m., originating in Rugerero sector in western Rwanda, according to the Rwanda Seismic Monitor.


Comment: Nyiragongo volcano erupts in DR Congo triggering evacuation in Goma - UPDATE


Seismograph

Major shallow magnitude 6.5 earthquake - Fiji: 266 Km SSE of Alo, Wallis And Futuna

Earthquake
© Associated Press
Date & time: 21 May 2021 22:13:18 UTC -

Local time at epicenter: 22 May 11:13 am (GMT +13)

Magnitude: 6.5

Depth: 10.0 km

Epicenter latitude / longitude: 16.6001°S / 177.3522°W (South Pacific Ocean, Fiji)