A Quieter Earth

Coronavirus lockdowns have changed the way Earth moves

A reduction in seismic noise because of changes in human activity is a boon for geoscientists.

 

 

View down a road, featuring tram lines, with a tall building at the end.

Residents of Brussels have been told to stay at home, leaving the city’s streets empty.Credit: Jonathan Raa/NurPhoto via Getty

The coronavirus pandemic has brought chaos to lives and economies around the world. But efforts to curb the spread of the virus might mean that the planet itself is moving a little less. Researchers who study Earth’s movement are reporting a drop in seismic noise — the hum of vibrations in the planet’s crust — that could be the result of transport networks and other human activities being shut down. They say this could allow detectors to spot smaller earthquakes and boost efforts to monitor volcanic activity and other seismic events.

A noise reduction of this magnitude is usually only experienced briefly around Christmas, says Thomas Lecocq, a seismologist the Royal Observatory of Belgium in Brussels, where the drop has been observed.

Just as natural events such as earthquakes cause Earth’s crust to move, so do vibrations caused by moving vehicles and industrial machinery. And although the effects from individual sources might be small, together they produce background noise, which reduces seismologists’ ability to detect other signals occurring at the same frequency.

Source: Royal Observatory of Belgium

Data from a seismometer at the observatory show that measures to curb the spread of COVID-19 in Brussels caused human-induced seismic noise to fall by about one-third, says Lecocq. The measures included closing schools, restaurants and other public venues from 14 March, and banning all non-essential travel from 18 March (see ‘Seismic noise’).

The current drop has boosted the sensitivity of the observatory’s equipment, improving its ability to detect waves in the same high frequency range as the noise. The facility’s surface seismometer is now almost as sensitive to small quakes and quarry blasts as a counterpart detector buried in a 100-metre borehole, he adds. “This is really getting quiet now in Belgium.”

Information boost

If lockdowns continue in the coming months, city-based detectors around the world might be better than usual at detecting the locations of earthquake aftershocks, says Andy Frassetto, a seismologist at the Incorporated Research Institutions for Seismology in Washington DC. “You’ll get a signal with less noise on top, allowing you to squeeze a little more information out of those events,” he says.

The fall in noise could also benefit seismologists who use naturally occurring background vibrations, such as those from crashing ocean waves, to probe Earth’s crust. Because volcanic activity and changing water tables affect how fast these natural waves travel, scientists can study these events by monitoring how long it takes a wave to reach a given detector. A fall in human-induced noise could boost the sensitivity of detectors to natural waves at similar frequencies, says Lecocq, whose team plans to begin testing this. “There’s a big chance indeed it could lead to better measurements,” he says.

Belgian seismologists are not the only ones to notice the effects of lockdown. Celeste Labedz, a graduate student in geophysics at the California Institute of Technology in Pasadena, tweeted that a similar fall in noise had been picked up by a station in Los Angeles. “The drop is seriously wild,” she said.

However, not all seismic monitoring stations will see an effect as pronounced as the one observed in Brussels, says Emily Wolin, a geologist at the US Geological Survey in Albuquerque, New Mexico. Many stations are purposefully located in remote areas or deep boreholes to avoid human noise. These should see a smaller decrease, or no change at all, in the level of high-frequency noise they record, she says.

from:    https://www.nature.com/articles/d41586-020-00965-x?utm_source=fbk_nnc&utm_medium=social&utm_campaign=naturenews&fbclid=IwAR11iBTZdpp9A4EBjzBZEYLi8YihTj0cSFU-0y8y_xdothehyh1grqmkDqg?utm_source=wnd&utm_medium=wnd&utm_campaign=syndicated

Unknown Fault Responsible for Utah Quake 3/24/20

After a 5.7 earthquake, Utah seismologists investigate a ‘virtually unknown’ fault

Soon after Salt Lake City stopped shaking March 18 from its strongest earthquake on record, Amir Allam, a University of Utah seismologist, knew he had to get busy if he hoped to closely study the hundreds of aftershocks he knew would follow the 7:09 a.m. jolt.

The fault that is believed to have moved along the eastern base of the Oquirrh Mountains is virtually unknown, and here was a chance, dropping out of the blue, to image it.

But Allam had a problem.

All 210 of the U.’s portable seismographs, loaf-sized instruments known as nodal geophones, were currently deployed along California’s San Andreas fault and elsewhere, and, therefore, were unavailable for what he needed to do in his own backyard. The Salt Lake Valley hadn’t had a sizable shake since 1962 and last week’s 5.7 magnitude earthquake offered a rare opportunity to better map the network of fractures under the valley.

Allam and his U. colleagues quickly mustered up dozens of geophones from other institutions and began burying them near the epicenter of the initial quake, likely on a fault that has remained a mystery to Utah seismologists.

They hope to characterize it and determine how it is interconnected with the Wasatch fault running along the base of the foothills on Salt Lake City’s east side and its lattice of associated faults, or “strands.”

‘Jury is still out’

“We started immediately the morning of the [initial] earthquake, and we have been installing them ever since,” Allam said Tuesday as he unloaded shovels and 43 geophones from his truck. “These are the last bunch.”

He already had deployed 139 geophones, each equipped with 35 days of battery life, around the Salt Lake Valley, each measuring ground movements — vertical, north-south and east-west — from hundreds of aftershocks. These recordings will help scientists with the U., as well as the Utah and U.S. geological surveys, to characterize this intriguing fault.

The Wasatch fault system’s network of cracks in the earth stretches 230 miles from Malad, Idaho south to Fayette, Utah through Utah’s major metropolitan area, where at least 80% of the population resides. A magnitude 6 quake on the main fault could cause severe damage, depending on where it strikes. A 2016 report forecast a 57% chance of such a quake or stronger within the next 50 years. Scientists do not believe last week’s temblor will reduce the chance of a major quake on the Wasatch fault down the road.

“We want to map out the basin depth all over the valley. We actually don’t know it [the fault network] that well,” Allam said. “… We want to capture as many tiny aftershocks as we can, so we have a really dense deployment around the epicenter of the 5.7 quake. We want to get that fault structure. We want to know exactly how the Wasatch and its subsidiary faults are changing their patterns in the subsurface.”

The fault that likely moved dips to the west and is not expressed on the surface, according to Kris Pankow of the U. Seismograph Stations. It could be the same one that shook Magna in 1962 with a magnitude 5.2 quake that touched off a swarm of lesser aftershocks, but it can’t be known for sure because the instrumentation was not in place to precisely locate that quake.

“The jury is still out on the specific fault that moved and produced [the March 18] earthquake,” said Ryan Gold, a research geologist with the U.S. Geological Survey. “The specific strand, that’s what we are trying to sort out. Additional instrumentation is being installed to monitor ongoing seismicity.”

‘Aftershocks are going to diminish’

(Francisco Kjolseth | The Salt Lake Tribune) University of Utah seismologist Amir Allam deploys 43 portable seismic instruments to be buried above Salt Lake City on Tuesday, March 24, 2020, to capture data following last week’s 5.7 magnitude earthquake.

In the week since the main quake, the ground under Magna has kept shaking.

As of Tuesday at 4 p.m., 456 aftershocks had been recorded, according to Gold, coming at an average rate of one every 20 minutes. At least 29 were magnitude 3 and a handful exceeded magnitude 4. The fault released a magnitude 3.1 temblor Tuesday at 5:32 a.m., followed by many stronger than magnitude 2. Most were located very close to the original epicenter a few miles north northeast of Magna and just six miles beneath the surface.

“The number and size of aftershocks are going to diminish with time but within these sequences. It’s the fault adjusting to the changes in stress. They are kind of chattering,” said Pankow, who is also closely monitoring aftershocks with larger seismographs placed in a few strategic locations. “With time, that stress is going to dissipate.”

The larger instruments are connected to broadband, providing real time data on the aftershocks. Meanwhile, satellite imagery shows the ground moved several centimeters at the surface as a result of the main quake, according to Gold.

The aftershocks don’t occur in steady intervals but in clusters, according to a graphic representation posted by Seismograph Stations. In the first three days after the mainshock, dozens of aftershocks flared. They grew weaker and less frequent until Sunday night, when a magnitude 4 struck, followed quickly by numerous aftershocks.

“That magnitude 4 was its own stress release; it has its own set of aftershocks to go with it,” Pankow said. “We might have some more magnitude 4s before this is all done.”

Seismometers, types of seismograph that measure surface ground movement, are installed in at least three major historic structures in downtown Salt Lake City: the Utah Capitol, City Hall and West High School. These instruments record direction, intensity and duration of earthquakes. The data generated by these instruments helps engineers understand the seismic forces buildings on the Wasatch fault system could be subject to, according to Pankow.

Hillside research

An assistant research professor in the U.’s Department of Geology and Geophysics, Allam teaches jiu jitsu on the side. On Tuesday, he recruited some of his students on a moment’s notice to help schlep instruments into the hills above Salt Lake City’s Avenues neighborhood as the weather deteriorated in front of a snowstorm expected to arrive by Wednesday.

They hoisted 50-pound satchels over their shoulders, each holding six geophones, and trekked a half-mile up the Bonneville Shoreline Trail to a spot where Allam had identified a 500-meter transect along a ravine that was just starting to green up with the coming of spring. Here the team was to plant the geophones along a preselected line spanning a known strand of the Wasatch fault in the undulating terrain overlooking the city.

As a cold rain began to fall, the crews dug 8-inch holes in 13-meter intervals along a downsloping ridgeline on a roughly north-south axis. The geophones were placed in the holes, oriented directly north, and covered with dirt.

In a month, Allam and his associates will return to recover 182 geophones around the valley. The harvest is hoped to yield a bounty of data that paints a valuable picture of what lurks beneath Utah’s most populated region.

from:    https://www.sltrib.com/news/environment/2020/03/25/fault-that-shook-magna/

Puerto Rico – Hit Again

A Major Earthquake Knocked Out Power Across Puerto Rico This Morning

Debris from a collapsed wall litters the ground in Ponce, Puerto Rico following the Jan. 7 earthquake.

Debris from a collapsed wall litters the ground in Ponce, Puerto Rico following the Jan. 7 earthquake.
(Image: © Carlos Giusti/AP/Shutterstock)
A magnitude 6.4 earthquake shook southwestern Puerto Rico this morning (Jan. 7), according to the U. S. Geological Survey (USGS); this is the largest yet in a series of quakes that have hit the region.

At least one person died as walls collapsed around the area, and eight more people were injured, according to NPR. Electricity went out across Puerto Rico as automated systems shut down the island’s power plants, recalling power outages that lasted 11 months after Hurricane Maria, which caused the worst blackout in US history. The North American and Caribbean tectonic plates meet in this area, but the quake doesn’t appear to be the result of those plates grinding together, according to USGS. Instead, a release of energy and stress inside the Caribbean plate seems to have caused the shaking.

A day earlier, a smaller, 5.8 magnitude quake in the same area destroyed a natural rock archway along the coast known as the Punta Ventana, NPR reported. Since a 4.7 magnitude earthquake struck the area on Dec. 28, 2019, more than 400 quakes of at least magnitude 2 have hit Puerto Rico’s southwest region. Eleven have been magnitude 4 or greater, according to USGS.

(The numbers used to measure quakes are nonlinear. A magnitude 3 quake is 10 times as powerful as a magnitude 2 quake, and a magnitude 4 quake is 10 times as powerful as a magnitude 3 quake and so on.)

Puerto Rico’s governor, Wanda Vázquez, suspended work for the day for public sector workers who aren’t first responders.

from:    https://www.livescience.com/major-earthquake-puerto-rico-january-7.html

What’s Going on in Oregon?

March 24, 2018 Update: “Something’s Not Right in Southern Oregon”

— “I have 2 large bird feeders and 2 hummingbird feeders that I’ve been refilling all winter — until about a week ago! Nothing — no birds! We also have a large population of geese that are always in our park, but nothing for over a week?”

– GG, Worried Resident, Grants Pass Oregon valley


“Are we about to experience a severe natural disaster?”

– Resident, Rogue Valley, Oregon on March 19, 2018

Rogue Valley, Oregon, is 11 miles north of Medford. It's in southwestern Oregon along the middle Rogue River and its tributaries in Josephine and Jackson counties near the California border. The largest communities in Rogue Valley are Medford, Ashland and Grants Pass.
Rogue Valley, Oregon, is 11 miles north of Medford. It’s in southwestern Oregon along the middle Rogue River and its tributaries in Josephine and Jackson counties near the California border. The largest communities in Rogue Valley are Medford, Ashland and Grants Pass.
Rogue Valley, Oregon, with the Crater Lake National Park 42°54′43″N 122°08′53″W to the east that encompasses the caldera of a destroyed volcano, Mount Mazama, and the surrounding hills and forests. Crater Lake is 1,949 feet (595 m) deep, which is the deepest lake in the United States.
Rogue Valley, Oregon, with the Crater Lake National Park 42°54′43″N 122°08′53″W to the east that encompasses the caldera of a destroyed volcano, Mount Mazama, and the surrounding hills and forests. Crater Lake is 1,949 feet (595 m) deep, which is the deepest lake in the United States.

UPDATE – March 24, 2018 Rogue Valley, Oregon – Since my March 19th Earthfiles report and March 21st Earthfiles YouTube Update about the puzzling and disturbing lack of birds in Rogue Valley, Oregon, near Medford, and possible link to impending earthquake in the Cascadia Subduction Zone there, I have received the following comments from viewers and listeners.

Return to Part 1.

1)

To: Linda Moulton Howe <earthfiles@earthfiles.com>
Re: Birds Also Missing in Grants Pass Oregon valley
Date: March 23, 2018

Morning,
I live in the Grants Pass Oregon valley. I have only lived here for a few years, but one of my joys of the valley is feeding my birds! Swallows, hummingbirds, robins throughout the season and especially the winter. I have 2 large bird feeders and 2 hummingbird feeders that I’ve been refilling all winter — until about a week ago! Nothing — no birds! We also have a large population of geese that are always in our park, but nothing for over a week?

We also own a home in the Smith River Oregon area. We have also noticed our large robin population has vacated?
We have lived in that area for over 40 years. The robins are always, always early morning feeders for us. Have not seen ANY in over a week?

We will be even more aware now to see what our large elk population and wildlife are doing….

GG,
Worried

To read more, go to link:      from:    https://www.earthfiles.com/2018/03/24/march-24-2018-update-somethings-not-right-in-southern-oregon/

Movement at the San Andreas Fault

Scientists discover a large-scale motion around San Andreas Fault

Scientists discover a large-scale motion around San Andreas Fault

A team of researchers from the University of Hawai’i at Mãnoa, University of Washington and Scripps Institution of Oceanography (SIO) analyzed the motion of Earth’s crust from the data collected by an array of GPS instruments placed near the San Andreas Fault System in Southern California. Their results revealed almost 201 km (125 miles) wide lobes of uplift and subsidence straddling the fault system. The motion has not been recorded so far, although it was predicted by theoretical models.

The GPS instruments record a vertical and horizontal motion of our planet’s surface. The tectonic motion of the crust, groundwater pumping, local surface geology, and precipitation amount all affect the vertical motion, and it was challenging to distinguish the broad, regional tectonic motion from the local motion.

The scientists have used comprehensive statistical methods to analyze the data recorded by the EarthScope Plate Boundary Observatory’s GPS network, and extract a large-scale pattern of smoothly varying vertical motions of the local crust.

San Andreas Fault in the Coachella Valley; from Keys View, February 12, 2014. Image credit: NPS/Robb Hannawacker/Joshua Tree National Park via Flickr-CC

 

“While the San Andreas GPS data has been publicly available for more than a decade, the vertical component of the measurements had largely been ignored in tectonic investigations because of difficulties in interpreting the noisy data. Using this technique, we were able to break down the noisy signals to isolate a simple vertical motion pattern that curiously straddled the San Andreas fault,” said Samuel Howell, a doctoral candidate at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST) and lead author of the study.

The results responded to those previously predicted by an earthquake cycle model, led by co-authors Bridget Smith-Konter, associate professor at SOEST, and David Sandwell, a professor at SIO.

Uplift (red) and subsidence (blue) based on GPS data (top) confirm predicted motion (bottom). Image credit: University of Hawai’i

“We were surprised and thrilled when this statistical method produced a coherent velocity field similar to the one predicted by our physical earthquake cycle models. The powerful combination of a priori model predictions and a unique analysis of vertical GPS data led us to confirm that the buildup of century-long earthquake cycle forces within the crust are a dominant source of the observed vertical motion signal,” said Smith-Konter.

New research suggests the scientists can use GPS vertical motion measurements to improve the understanding of the structure and behavior of faults, even when no major ruptures occurred for decades or, even, centuries. Results are expected to contribute to constraining the seismic hazard estimates from the San Andreas Fault System, and could enable mapping of the large-scale motion resulting from the next significant rupture of the fault, in more detail.

Reference:

  • “The vertical fingerprint of earthquake cycle loading in southern California” – Samuel Howell, Bridget Smith-Konter, Neil Frazer, Xiaopeng Tong & David Sandwell – Nature Geoscience (2015) – doi:10.1038/ngeo2741

Featured image: San Andreas fault in the Coachella Valley; from Keys View, February 12, 2014. Image credit: NPS/Robb Hannawacker/Joshua Tree National Park via Flickr-CC

from:    http://thewatchers.adorraeli.com/2016/06/21/scientists-discover-a-large-scale-motion-around-san-andreas-fault/

Induced Earthquakes

(To check out the image, go to:  http://www.livescience.com/54212-oklahoma-is-now-earthquake-hotspot.html)

Man-Made Earthquake Hotspot Revealed: Oklahoma
by Laura Geggel, Staff Writer

The chances of a damaging earthquake occurring in parts of Oklahoma and some neighboring states are just as likely as they are in temblor-heavy California, according to a report by the U.S. Geological Survey (USGS).

The culprit? Man-made activities related to oil and gas production are creating the shaky conditions in a region of the central and eastern U.S., the USGS seismologists say.

USGS scientists just released their first map that includes earthquake risks from both natural and human-induced causes for the coming year. Until now, the government agency included only temblor risks linked to natural causes.

The report, which is part of a 50-year forecast examining earthquake hazards, reveals that about 7 million people live and work in areas at risk of human-induced seismicity. Areas in the central and eastern U.S. (CEUS) are at risk of experiencing a quake of the same magnitude as those that occur naturally in California, the USGS said. [Image Gallery: This Millennium’s Destructive Earthquakes]

“By including human-induced events, our assessment of earthquake hazards has significantly increased in parts of the U.S.,” Mark Petersen, chief of the USGS National Seismic Hazard Mapping Project, said in a statement. “This research also shows that much more of the nation faces a significant chance of having damaging earthquakes over the next year, whether natural or human-induced.”

The CEUS’ induced earthquakes are often the product of wastewater disposal, the USGS said. This wastewater comes from oil and gas production, when it is pumped into underground wells deep in the Earth. This is different from hydraulic fracturing, also known as fracking, in which water, sand and chemicals get pumped into the Earth to break up rock and extract oil and gas. The actual fracking is probably a more infrequent cause of felt earthquakes, the USGS said. (Wastewater from fracking is generally pumped back into wastewater injection wells.)

Still, wastewater injection practices have put six states on the earthquake map. Oklahoma has the highest risk, followed by Kansas, Texas, Colorado, New Mexico and Arkansas, the USGS reported. Oklahoma and Texas have the largest populations living near induced-earthquake hotspots.

“In the past five years, the USGS has documented high shaking and damage in areas of these six states, mostly from induced earthquakes,” Petersen said. “Furthermore, the USGS Did You Feel It? website has archived tens of thousands of reports from the public who experienced shaking in those states, including about 1,500 reports of strong shaking or damage.”

For instance, from 1973 to 2008, an average of 24 earthquakes with a magnitude of 3.0 or higher shook the central United States in each of those years. But, from 2009 to 2015, that number increased to an average of 318 earthquakes of that magnitude per year. 2015 saw the greatest number, with 1,010 earthquakes of a magnitude 3.0 or greater. [Video: Watch 2,500+ Earthquakes in Oklahoma Linked to Humans]

And through mid-March of this year, 226 earthquakes of a magnitude 3.0 or higher have already hit the central United States, the USGS said. The largest earthquake to occur near a wastewater injection site was a magnitude-5.6 temblor near Prague, Oklahoma, in 2011.

Overall, USGS researchers found 21 areas with increased rates of human-induced seismicity. Some areas — such as regions within Alabama and Ohio — experienced human-induced earthquakes in the past, but have relatively little risk in the coming year because the activities that caused these quakes have decreased.

But other areas of Alabama and some parts of Mississippi have shown an increase in these activities. But researchers are still determining whether earthquakes in these areas happened naturally or were human-induced, the USGS said.

The scientists found the greatest risk of a human-induced earthquake in north central Oklahoma and the southernmost part of Kansas. They calculated that there is a 10 to 12 percent risk that an earthquake with strong shaking will occur in those areas this year. Such an earthquake, they estimated, would register a 6 or greater on the Modified Mercalli Intensity scale, meaning it would easily be felt but would likely cause just slight damage. This translates into about a 5.0 on the Richter scale.

Though scientists disagree about whether wastewater injection leads to larger or smaller earthquakes compared with natural ones, in the CEUS region, when a large temblor does strike, thousands of faults could rupture, according to the USGS. What’s more, human-induced quakes tend to come in swarms of smaller events at shallower depths, whereas shaking is more likely to be felt and cause damage.

The new earthquake report will help architects determine how to safely design buildings within areas of high risk. People who live in earthquake territory can read about safety measures at FEMA’s Ready Campaign.

 

from:    http://www.livescience.com/54212-oklahoma-is-now-earthquake-hotspot.html

Rare Nevada Earthquake

12/11/2015 — Earthquake strikes Volcanoes next to famous AREA 51 base in Nevada

A rare M3.1 earthquake has struck the volcanoes next to the famous “AREA 51” base in Southern Nevada.

three volcanoes struck in 12 hours time dec 11 2015
Above: Past 12 hours of earthquakes (up to 930am CT December 11 2015) , showing M2.7 and greater in the United States. The epicenters of the events show the only locations to experience any noteworthy movement are three dormant volcanic fields.

________

Do not confuse this with a “UFO crash” (lol!) or a bombing range test — the depth of the earthquake was at over 8km / 5 miles below the surface.

This movement at the ancient volcanic complex next to Area 51 is part of a much larger seismic event underway (currently) on the West coast of the United States.

area 51 earthquake volcano dec 11 2015
Above: Google Earth search of the USGS earthquake coordinates shows the M3.1 earthquake striking between the long dormant AREA 51 volcanic fields at a depth of over 5 miles.

________

In addition to the long dormant (extinct) volcanoes next to Area 51 showing activity, we see that the ONLY other locations to have M3.0+ activity are other volcanic locations to the North and South.

The swarm of earthquakes to the North struck Challis Idaho, which is the Westernmost portion of the Yellowstone Magma chamber, and a location where a man was almost killed in geothermal activity a few months ago.

Challis, ID is also the location where the USGS went to install new monitoring equipment after a M5.0+ earthquake struck the location 2 years ago.

4.9 yellowstone idaho earthquake april 12 2014

________

To the South of the Area 51 earthquake location , Cerro Prieto volcano showed up with an earthquake swarm as well, topping out at M3.1 in power.

This dormant volcano was forecast to show movement in the most recent earthquake forecast video issued on December 8, 2015.

cerro prieto earthquake forecast dec 11 2015

_______

See the forecast calling for Cerro Prieto volcano to show movement here:

________

Overall, this seismic unrest at the dormant volcanoes along the West coast was expected.

The locations which are showing movement were all named out in the above forecast video, literally called out each location by name , Central Idaho (Challis), California border (Cerro Prieto), and Western Nevada near the California border.

_______

Information on the AREA 51 earthquake from the USGS:

http://earthquake.usgs.gov/earthquakes/eventpage/nn00522233#scientific_origin:nn_nn00522233

from:    http://dutchsinse.com/

Cluster of Quakes Near San Francisco

Questions, answers on cluster of quakes near San Francisco

Associated Press

SAN RAMON, Calif. (AP) — A swarm of small earthquakes has been rattling an area east of San Francisco, with more than 200 recorded since last week.

All the quakes were centered around the city of San Ramon on either the Calaveras Fault or offshoots of it. The largest struck Monday and was logged as a magnitude-3.5, according to the U.S. Geological Survey. No injuries or major damage have been reported.

Experts say such swarms are not unusual or cause for extra concern. Here are the basics on the temblors and what to expect:

IS A SWARM LIKE THIS A PRECURSOR TO A BIGGER EARTHQUAKE?

The San Ramon, Danville and Alamo area has seen several swarms over the past 40 years, U.S. Geological Survey Research Geophysicist Brad Aagaard said. The largest earthquake in each was in the magnitude 3.5 to 4.4 range.

Based on this historical data, Aagaard says, the most recent swarm is unlikely to lead to a large, damaging earthquake.

Several of the swarms have lasted about 30 to 40 days, so East Bay residents likely will continue to experience light shaking for a couple more weeks.

___

DOES A SWARM RELIEVE PRESSURE TO AVOID A BIGGER QUAKE?

These small earthquakes relieve only a very tiny amount of stress compared with a magnitude-6.0 or larger earthquake. As a result, they do not reduce the occurrence of larger earthquakes.

___

HOW LIKELY IS A LARGE EARTHQUAKE ON THE CALAVERAS FAULT?

The probability of a magnitude-6.7 or larger quake on the northern section of the Calaveras fault in the next 30 years is 8 percent.

The probability of a magnitude-6.7 or larger earthquake somewhere in the San Francisco Bay Area region in the next 30 years is 72 percent.

___

WHAT SHOULD PEOPLE DO TO PREPARE FOR A BIG EARTHQUAKE?

Experts suggest keeping a gallon of water per person per day for at least three days, for drinking and sanitation. They also recommend having a three-day supply of nonperishable food.

Officials say people should have an earthquake preparedness kit with a flashlight, extra batteries, a battery-powered or hand crank radio and a National Oceanic and Atmospheric Administration radio with tone alert.

Other items to have include a first-aid kit, a whistle to signal for help, a dust mask to help filter contaminated air, as well as plastic sheeting and duct tape to shelter in place. Maps, a can opener, a wrench or pliers to turn off utilities, as well as moist towels and garbage bags for personal sanitation are also advisable.

___

Information from: KGO-TV.

http://news.yahoo.com/questions-answers-cluster-quakes-near-san-francisco-190513998.html

3D Earthquake Mapping

Mapping 100 Years of Earthquakes, in 3-D

Between 1900 and 2015, there have been more than 10,000 “strong” quakes around the world

(Richie Carmichael)

Since 1900, there have been more than 10,000 “strong” earthquakes—with magnitudes of 6 or greater—around the world, according to the U.S. Geological Survey. But what exactly does that look like?

Richie Carmichael, a software developer at Esri, a company that provides geographic information system (GIS) software, has created a visualization of all that seismic activity: an interactive 3-D globe. Using data from USGS and Wikipedia, Carmichael plotted where and how large earthquakes were in any given year between 1900 and 2015.

“A 3-D display is uniquely suited to representing global phenomena,” says Carmichael in an email. “Print and digital 2D maps are often truncated on or near the poles and close the international date line. With a globe it is possible to view quakes in the polar regions and pacific without page breaks.”

Users can rotate the virtual globe to see a specific area, and filter the data by the largest or deadliest earthquakes, as well as by the cause of the quakes—like those brought on by nuclear activity.

In the chart below the globe, the clustering of dots—each dot representing one event—seems to suggest that earthquakes are becoming more frequent. Indeed, a recent study by USGS researchers found that there were more than twice as many “large” earthquakes (defined here as magnitudes 7 or above) in the first quarter of 2014 than there were back in 1979. The planet saw a record number of earthquakes last April, with 13 quakes with magnitudes of 6.5.

“We have recently experienced a period that has had one of the highest rates of great earthquakes ever recorded,” according to Tom Parsons, a research geophysicist at USGS.

But this doesn’t mean “The Big One” is coming. Most researchers agree that the frequency spike is most likely random. Plus, this isn’t the first time we’ve seen an uptick in quakes: between 1950 and 1965, the earth shook more than usual, too. As the USGS explains, “A temporary increase or decrease in seismicity is part of the normal fluctuation of earthquake rates. Neither an increase or decrease worldwide is a positive indication that a large earthquake is imminent.” In fact, Parson’s study shows that since 1979, the average rate of major earthquakes has been roughly 10 a year.

What has increased, however, is the quality of surveillance. The USGS has more than 2,000 seismic sensors—many of which are in the U.S—and the agency plans to eventually establish a network of more than 7,000 sensors in the U.S. alone. That will allow for denser coverage in at-risk urban areas. To better track quakes outside of the U.S. border, the agency has tapped into the power of Twitter, monitoring tweets to detect quakes in as little as 29 seconds after an event.

As detection has become more advanced, so has earthquake-resistant technology. Recently, a San Francisco hospital became the first U.S. building to use a thick goo that can absorb 80 to 90 percent of an earthquake’s energy. And in India, civil engineers are testing the use of old crushed tires to strengthen the base of buildings to reduce vibration. Their test has shown that when the rubber is mixed with sand, it’s possible to improve seismic resistance by as much as 50 percent.

This is a good thing, since Bill McGuire, a professor at the geophysical and climate hazards at University College London, suggests that the ever-changing climate could very will shake up the Earth more in the future. As temperatures rise rise—along with sea levels—more stress will be put on the crust of the Earth:

GPS measurements reveal that the crust beneath the Greenland ice sheet is already rebounding in response to rapid melting, providing the potential—according to researchers—for future earthquakes, as faults beneath the ice are relieved of their confining load. The possibility exists that these could trigger submarine landslides spawning tsunamis capable of threatening North Atlantic coastlines. Eastern Iceland is bouncing back too as its Vatnajökull ice cap fades away. When and if it vanishes entirely, new research predicts a lively response from the volcanoes currently residing beneath. A dramatic elevation in landslide activity would be inevitable in the Andes, Himalayas, European Alps and elsewhere, as the ice and permafrost that sustains many mountain faces melts and thaws.

“The bottom line is that through our climate-changing activities we are loading the dice in favour of escalating geological havoc at a time when we can most do without it,” he concludes. We best speed up those tests on infrastructure that can resist quake damage—especially in cities.

http://www.citylab.com/weather/2015/10/mapping-100-years-of-earthquakes-in-3d/409894/

Southern CA Earthquake

Moderate earthquake – Southern California on September 16, 2015

Last update: September 16, 2015 at 4:56 pm by By

Update 16:24 UTC : Max. light shaking near the epicenter (as expected)

Screen Shot 2015-09-16 at 18.23.47

Update 16:19 UTC :  As the earthquake happened in a rocky area, we do not think that severe damage would be registered. Slight damage is certainly a possibility.

Screen Shot 2015-09-16 at 18.18.15

13km (8mi) SSE of Big Bear Lake, California
14km (9mi) S of Big Bear City, California
20km (12mi) NE of Yucaipa, California
40km (25mi) E of San Bernardino, California
41km (25mi) NE of Moreno Valley, California
46km (29mi) NW of Palm Springs, California
84km (52mi) S of Barstow, California

Most important Earthquake Data:

Magnitude : 4

Local Time (conversion only below land) : 2015-09-16 09:10:47

GMT/UTC Time : 2015-09-16 16:10:47

from:    http://earthquake-report.com/2015/09/16/moderate-earthquake-southern-california-on-september-16-2015/