Tag Archives: seismic

The coronavirus-induced anthropause is now visible in seismic vibrations

Every step you take is a micro-earthquake — it produces tiny vibrations that propagate through the Earth. Other human activities, like construction and traffic, produce stronger vibrations that researchers can detect using instruments called seismometers.

In a new study, researchers report a near-global 50% drop in this seismic noise. This is the first global study of the pandemic on the solid Earth beneath our feet.

These tiny seismometers were instrumental in the study. Image credits: Imperial College London.

The anthropause

I was but a wee student when our university group got to see a seismograph. It was an old unit, hidden in a dusty university room. As we were getting a brief lecture on how it works, the needle suddenly started to move, and we all freaked out a bit.

“That’s just the subway,” we were told.

Sure enough, a subway station was nearby, but the fact that human activities such as public transit can create seismic vibrations was an eye-opener.

In fact, not only is human activity detectable on seismic sensors, it’s an active problem. In some instances, humans produce so much noise that they distort information from actual earthquakes. For the last few months, however, that kind of stopped.

As the pandemic forced human activity to slow or shut down entirely, the noise lessened, says Dr. Stephen Hicks from Imperial’s Department of Earth Science and Engineering, co-author of the study:

“This quiet period is likely the longest and largest dampening of human-caused seismic noise since we started monitoring the Earth in detail using vast monitoring networks of seismometers.”

“Our study uniquely highlights just how much human activities impact the solid Earth, and could let us see more clearly than ever what differentiates human and natural noise.”

Example of activity drop in urban area. Image credits: Lecocq et al.

Although the earthquake activity has proceeded as normal, the seismic noise has dropped considerably, particularly in urban areas. We know this type of thing can happen as we’ve seen it briefly around New Years and Christmas when activity quiets down — but never on such a scale.

Some researcherrs are already calling this period the ‘anthropause’, the break in human activity. There are many ways to see the anthropause in action, from a drop in pollution levels to reduced mobility, and now, in seismic activity.

Do the Raspberry Shake

To get a clear picture of how the anthropause is ‘visible’ in the subsurface, researchers used data from 268 stations in 117 countries, even using some citizen seismometer stations such as Raspberry Shakes. Technology such as the Raspberry Pi (a credit-card sized computer, which the Raspberry Shake is also based on) has opened up a new world of scientific projects, including seismic research.

Researchers observed the effects of lockdowns starting in late January 2020 in China, and then expanding into Europe and the rest of the world from March onwards. The noise level reduction was, at times, larger than that observed over Christmas or New Years. The largest drop in vibrations was observed in the densest-populated areas such as Singapore and New York City, but the team also observed the anthropopause in remote areas such as Germany’s Black Forest and the town of Rundu in Namibia.

The global reduction in seismic noise. Image credits: Lecocq et al.

In addition to being an interesting view at the drop in human activity, this also highlights the problems of the day-to-day noise associated with things like traveling, drilling, and construction.

Researchers often monitor hazardous areas using seismic information. If our activity is concealing these natural signals, it may be increasingly difficult to predict impending hazards (such as landslides or volcanic eruptions).

“With increasing urbanisation and growing global populations, more people will be living in geologically hazardous areas,” explained seismologist and lead author Thomas Lecocq of the Royal Observatory of Belgium.

“It will therefore become more important than ever to differentiate between natural and human-caused noise so that we can ‘listen in’ and better monitor the ground movements beneath our feet. This study could help to kick-start this new field of study.”

The study’s authors hope that their work will inspire other further research on the seismic lockdown Dr. Hicks concludes:

“The lockdowns caused by the coronavirus pandemic may have given us a glimmer of insight into how human and natural noise interact within the Earth. We hope this insight will spawn new studies that help us listen better to the Earth and understand natural signals we would otherwise have missed.”

NASA presents first insights from Martian earthquakes

A whopping 174 seismic events have been recorded by the lander’s seismometer on Mars, indicating an active plate with intriguing tectonics.

Artist’s rendition of NASA’s lander. Image credits: NASA / JPL.

If we once thought Mars was a barren and boring place, there’s no reason to believe that now. Not only did the Red Planet host liquid water and an atmosphere, it still seems to have some semblance of a tectonic system.

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (or InSight) mission was launched in 2018 to study the subsurface of the planet. The plan was fairly straightforward: send a lander on Mars, and deploy a few geological sensors, including a seismometer and a thermal probe. The goal is to study Mars’ early geological evolution, understanding how it formed and evolved, and whether it is active today.

InSight (shown as a star) landed on an ancient volcanic plain south of Elysium Mons and north of the Martian “equator”. Image credits: Banerdt et al, Nature Geoscience.

Seismic sensors offered invaluable information here on Earth. Most of what we know about the Earth’s depths comes from seismic information — the way seismic waves propagate through the crust, mantle, and core, can help us understand their size and physical properties. While a single sensor would be limited in scope, it would still offer an unprecedented view into the Martian depths.

“This is the first mission focused on taking direct geophysical measurements of any planet besides Earth, and it’s given us our first real understanding of Mars’ interior structure and geological processes,” said Nicholas Schmerr, an assistant professor of geology at UMD and a co-author of the study. “These data are helping us understand how the planet works, its rate of seismicity, how active it is and where it’s active.”

In a flurry of new papers, NASA researchers presented the first findings from InSight, including the identification and study of almost two hundred earthquakes.

Comparison between seismic waves from two marsquakes (top, brown) and two earthquakes (bottom, blue). Image credits: Banerdt et al, Nature Geoscience.

The waveforms of the seismic waves showed that most earthquakes were high-frequency and low-intensity.

However, over 20 earthquakes had a magnitude of 3-4, and several were low-frequency (potentially indicative of tectonic movement). Three showed wave patterns distinctly similar to tectonic quakes on Earth. Researchers believe that they might be able to identify the source of these earthquakes.

“These low-frequency events were really exciting, because we know how to analyze them and extract information about subsurface structure,” said Vedran Lekic, an associate professor of geology at UMD and a co-author of the study. “Based on how the different waves propagate through the crust, we can identify geologic layers within the planet and determine the distance and location to the source of the quakes.”

In addition to the seismometer, the mission also deployed the first ground-based magnetometer, capable of studying the planet’s crustal magnetic field. Although satellite missions have also measured crustal magnetization, land-based surveys can provide more detailed and precise information about the planet’s localized magnetic field. Measurements showed a stronger-than-anticipated magnetic field, consistent with an Earth-like ancient dynamo field that would have been capable of supporting an atmosphere.

This further emphasizes Mars’ past as an active, Earth-like planet.

The seismometer’s delicate sensors also provided important information about Martian weather. For instance, when strong winds lift the ground significantly, the seismometer registers a tilt in the substrate. Researchers found that these winds produce a distinct seismic signature, which, along with direct weather information, can paint a picture of daily meteorological activity.

The team reports that the winds start picking up steam at midnight, becoming stronger through the early morning, as cooler air rolls down from the highlands to the plain where the lander is carrying out its activity. This wind activity produces enough noise to mask the seismic activity during the day. From late evening until midnight, conditions become very quiet around the lander, and it’s during the night — and it’s in that period that almost all the seismic events were detected. It’s almost certain that the activity continues outside thous hours, but there’s just too much noise to detect the seismic waves.

“What is so spectacular about this data is that it gives us this beautifully poetic picture of what a day is actually like on another planet,” Lekic said.

The research papers, “First constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data,” P.Lognonné et al., and “Initial results from the InSight mission on Mars” by W. Banerdt et al., were published as part of a special issue of the journal Nature Geoscience released on February 24, 2020.


NASA eavesdropped on the Sun, and they made a video so you can hear it too

With a bit of help from NASA, you can now hear the sun’s roar — and it’s glorious.


The Sun’s surface seen in ultraviolet light, colored by NASA.
Image credits NASA Goddard.

Although you never hear it, the Sun is actually pretty loud. This massive body of superheated, fusing plasma, is rife with ripples and waves generated by the same processes that generate its light and heat — and where there’s motion, there’s sound. We never get to hear it, however, as the huge expanse of nothing between the Earth and the Sun acts as a perfect acoustic insulator.

With some of ESA’s (the European Space Agency) data and a sprinkling of NASA’s magic, however, you can now hear the Sun churn in all of its (surprisingly tranquil) glory.

Hear me roar (softly)

“Waves are traveling and bouncing around inside the Sun, and if your eyes were sensitive enough they could actually see this,” says Alex Young, associate director for science in the Heliophysics Science Division at NASA’s Goddard Space Flight Center.

What Young is referring to are seismic waves, a type of acoustic waves — the same kind of motion that causes earthquakes in rocky planets — that form and propagate inside the Sun. Hypothetically, if you were to look at the star with the naked eye, you could actually see these waves rippling through its body and surface. Stars are formed of a much more fluid material than most planets, and so their bulk flows more readily under the sway of seismic waves — wiggling just like a poked block of Jell-O.

As most of us learned in early childhood, however, one cannot look directly into the Sun for long. Luckily for us, ESA recently embarked on a one-of-a-kind mission: they sent the Parker Solar Probe hurtling towards our star. Using its SOHO Michelson Dopler Imager (MDI) instrument, the probe recorded these motions inside the Sun. Researchers at NASA and the Stanford Experimental Physics Lab later processed into a soundtrack.

It’s not half-bad, as far as tunes go. I actually find it quite relaxing. Check it out:

[panel style=”panel-info” title=”Hear me roar” footer=””]

The sounds you hear in NASA’s clip are generated by the motions of plasma inside the Sun. These are the same processes that generate local magnetic fields inside the star and push matter towards the surface, causing sunspots, solar flares, or coronal mass ejections — the birthplace of space weather.

Space weather phenomena are associated with intense bursts of radiation, to which complex technological systems are susceptible. So most of our infrastructure, from satellites — and with them, cell phone networks, GPS, and other types of communication — transportation, and power grids.[/panel]

It took a great deal of work to turn the readings from Parker into something usable. Alexander Kosovichev, a physicist at the Stanford University lab, processed the raw SOHO MDI data by averaging Doppler velocity data over the solar disc and then only keeping low degree modes. These low degree modes are the only type of seismic waves whose behavior inside stars is known and accessible to helioseismologists. Afterward, he cut out any interference, such as sounds generating by whizzing of instruments inside the craft. He then filtered the data to end up with uninterrupted sound waves.

While scientists probably enjoy a groovy track just as much as the rest of us, the soundtrack actually has practical applications. By analyzing the sounds, researchers can get a very accurate picture of the churnings inside of our Sun — much more accurate than previous observations could provide.

“We don’t have straightforward ways to look inside the Sun,” Young explains. “We don’t have a microscope to zoom inside the Sun. So using a star or the Sun’s vibrations allows us to see inside of it.”

A more comprehensive understanding of the motions inside the Sun could allow researchers to better predict space weather events.

Story via NASA.

Aerial image of Cleveland Volcano. (c) Alaska Volcano Observatory

Alaskan volcano shows signs of eruption

Aerial image of Cleveland Volcano. (c) Alaska Volcano Observatory

Aerial image of Cleveland Volcano. (c) Alaska Volcano Observatory

Increased heat emissions by a volcano located in the Aleutian were detected via satellite by the Alaska Volcano Observatory, which has issued an eruption advisory alert. Recent activity has increased the volcano to a Yellow Alert.

Mt. Cleveland, 5,676 ft. AGL, also referred to as Cleveland volcano is emitting seismic activity that seems to correlate with the heat emission reports. These measurements indicate the volcano could erupt at any moment, spewing ash clouds up to 20,000 feet (3.7 miles/6 km) above sea level with little further warning, the observatory said.
Located on a deserted island, 45 miles west of Nikolski and about 150 miles west of Unalaska/Dutch Harbor, in case of an eruption Cleveland is too far off any major settlements to cause any damage. A great incovenience might lay, however, with the International Trans-Pacific flights using the great circle route make flights daily over this portion of the Aleutian Islands. So far, airlines have not changed their flight patterns because of Cleveland’s heat emissions, said Steve McNutt, a University of Alaska Fairbanks scientist who works at the observatory.
The last time Clevaland erupted was in 2001, when it blasted ash more than 5 miles (8 km) into the sky and spilled lava from the summit crater. Cleveland has experienced several smaller eruptions or suspected eruptions since then.
Volcanoes are pretty unpredictable, and although scientists know from current measurements that its at risk of eruption, they can’t tell without a real-time seismic network at Cleveland, AVO when its going to eventually pop-out exactly. It could happen tomorrow, or just as well ten years from now.
“Short-lived explosions with ash clouds that could exceed 20,000 ft. above sea level can occur without warning and may go undetected on satellite imagery for hours. Low-level ash emissions at Cleveland occur frequently and do not necessarily mean a larger eruption is imminent.  AVO continues to monitor the volcano using satellite imagery,” website source explain.

Massive 7.9 magnitude earthquake hits Japan, creates tsunami

It’s been a busy tectonic month, and things aren’t about to chill down. A massive 7.9 magnitude Earthquake has just hit the Northern coast of Japan, triggering a more than four meter tall tsunami that wiped down cars and other property along the coastline, but it’s still unclear how many people were injured or killed. What is also unclear, and shocking to me, is that in the rush of events, some sources reported the earthquake as having a magnitude of 8.9, which would make the earthquake 10 times more powerful.

The national broadcaster, NHK, showed footage of dozens of cars and ferries being washed up on the beach, but additional details are still unavailable. The Japanese Meteorological Agency issued a tsunami warning for the entire Pacific Japanese coast, and residents in the coastal areas have been urged to evacuate and more deeper inland, to higher grounds.

The earthquake, which took place in the Earth’s crust, struck about 125 km off the northern coast, at an estimated depth of 10 km, and is expected to generate further tsunamis with waves of 6-7 meters, especially in the Miyagi Prefecture, in northeastern Japan, where the earthquake’s intensity was 7.

Earthquake’s magnitude and intensity should not be confused, as the magnitude measures the amount of energy released by the earthquake, so it’s the same for everybody in the world, while intensity refers to the felt intensity and damage caused by an earthquake, so this varies from area to area for the same event.

Los Angeles way overdue for major earthquake

Image courtesy of University of Oregon

It’s time we face it, a big one is coming – and soon ! All the predictions point towards a major earthquake near the San Andreas fault in a short time, and Los Angeles will suffer the most of it. A recent study published in the Bulletin of the Seismological Society of America confirmed that the Los Angeles basin is way overdue for a major earthquake, and by more than a century; they came to this conclusion after setting an earthquake chronology of the San Andreas fault.

Their results showed seven major earthquake events: 905-961 AD, 959-1015 (possible), 1090-1152, 1275-1347, 1320-1489 (possible), 1588-1662 and 1657-1713, based on radiocarbon dates and analysis of the seismic structures preserved in the sediment.

The fact that a major earthquake is threatening California isn’t what you would call breaking news, but considering the fact that earthquakes took place ever 100-150 years, and the last one was 300 years ago shows just how long overdue this earthquake is. Ray Weldon, professor and head of the department of geological sciences at the University of Oregon, documents that the south end of the San Andreas fault has gone perhaps 140 years longer without a significant seismic event than expected.

“We have dated the last five to seven prehistoric earthquakes of the southernmost 100 kilometers (about 60 miles) of the San Andreas Fault, which is the only piece of the fault that hasn’t ruptured in historical times,” Weldon said. “If you were there in about 1690, when the last earthquake occurred, the odds of getting to 2010 without an earthquake would have been 20 percent or less.”

Sadly, the scientific community seems more concerned about this than the people from Los Angeles who should be getting prepared for the unevitable earthquake that will come – and soon.