Background noise and less seismic activity caused by humans during COVID-19

Measuring seismic activity often requires locating instruments away from population centers. During COVID-19, the seismic activity caused by humans dropped a lot:

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Photo by George Becker on Pexels.com

Writing today in the journal Science, dozens of researchers from around the world show that the seismic activity from our civilization plummeted as lockdowns went into effect. This “anthropogenic seismic noise,” as seismologists call it, comes from all manner of human activities, whether that’s running factories, operating cars or trains, or even holding concerts. Seismometers pick up these activities as a kind of constant din, which actually peaks on weekdays, when more people are moving around, and falls on weekends when economies slow down. All this activity that seismometers detect mixes with the natural rumbles that scientists are really interested in, like earthquakes, volcanoes, and landslides.

But boy, are they interested in the anthropogenic seismic noise now—or the lack thereof, as humans began to shelter in place. “We see it effectively moving around the globe as a seismic lockdown wave,” says Royal Holloway University of London seismologist Paula Koelemeijer, one of the paper’s coauthors. “So starting in China originally, then in different places in Italy, and then going through Europe. And whenever lockdowns happened in different countries, we see the effect that’s up to an 80 percent reduction in the amplitude of the seismic noise in some places.” The average was about 50 percent…

Normally, seismologists don’t bother monitoring urban environments for just this reason: There’s way too much noise muddying the signals of Earth’s natural processes. But for the past few years, citizen scientists have been collecting signals thanks to a clever little device called the Raspberry Shake, a Raspberry Pi computer outfitted with sensors to create an internet-connected seismometer. “Those instruments have been popping up more and more in people’s homes,” says Koelemeijer. “And so about 40 percent of our data stations that we looked at have been these citizen science instruments. It’s just people finding it funny, geeky, to have one of them. Like, I’m one of those people. I have one in my house.”…

But it was in a remote part of Germany where seismologists recorded perhaps the most surprising lockdown data. The Black Forest Observatory is not only isolated, and thus considered to be a reference low-noise laboratory, but its instruments are stowed over 150 meters below the surface, in bedrock. Yet they, too, picked up a small noise reduction at night during the lockdown. “Germany was a big surprise for us, because that station is very much a remote station, and seen as a very good seismic station for looking at natural signals,” says Koelemeijer. “So the fact that we saw it there was quite remarkable.”

Human activity influences all sorts of spheres that we do not often consider. Here, humans create a lot of noise and activity below the surface of the earth. There are occasionally complaints about noise pollution but most people put up with a certain amount of noise and vibrations in the places where they live.

This reminds of several different aspects of working with “background noise.” Working in radio, I often used sound effects for promotional material. The sound effect CDs we had contained a variety of background noise or din. For example, the city options largely contained traffic noise with vehicle rumbling and honking mixed together.

More recently, sports broadcasts have adjusted to teams playing in stadiums with no fans present in the stands. They often use recordings of fans where a sound technician has the ability to respond to play on the field (such as cheering for a good play for the home team or a negative response from fans). Without such background noise, the broadcast sounds very different: voices echo, the players can be heard, and a comforting or familiar element of the broadcast is lost.

All together, the background noise of our lives matters in everyday activity and in scientific measurement. If COVID-19 changes human movement and interactions, what we hear by ear and scientific instruments also changes.

Determining whether concrete buildings in LA are endangered by earthquakes

The Los Angeles Times looks at a number of concrete buildings in LA that could be at serious risk in an earthquake:

Despite their sturdy appearance, many older concrete buildings are vulnerable to the sideways movement of a major earthquake because they don’t have enough steel reinforcing bars to hold columns in place.

Los Angeles officials have known about the dangers for more than 40 years but have failed to force owners to make their properties safer. The city has even rejected calls to make a list of concrete buildings.

In the absence of city action, university scientists compiled the first comprehensive inventory of potentially dangerous concrete buildings in Los Angeles.

The scientists, however, have declined to make the information public. They said they are willing to share it with L.A. officials, but only if the city requests a copy. The city has not done so, the scientists said.

Pretty interesting look at how concrete buildings can be built to withstand earthquakes. The key issue here seems to be retrofitting: should it be required and if so, how much would property owners complain about the cost? As the article notes:

Earthquake safety has rarely been an issue that draws deep public passions and outrage. Most seismic regulations are approved in the wake of destructive earthquakes, but there hasn’t been one in California in nearly 20 years.

In other words, occasional disasters allows room for complacency. When the events are rare, people will question whether the money should be better spent elsewhere. This is part of the debate over other disasters as well like: how should buildings in Tornado Alley be constructed if tornadoes might occur? Should New York be protected from hurricanes and rising water levels by constructing gates and barriers? How much should be spent on levees in New Orleans to avoid situations like that after Hurricane Katrina?

Modeling “wordquakes”

Several researchers suggest that certain words on the Internet are used in patterns similar to those of earthquakes:

News tends to move quickly through the public consciousness, noted physicist Peter Klimek of the Medical University of Vienna and colleagues in a paper posted on arXiv.org. Readers usually absorb a story, discuss it with their friends, and then forget it. But some events send lasting reverberations through society, changing opinions and even governments.

“It is tempting to see such media events as a human, social excitable medium,” wrote Klimek’s team. “One may view them as a social analog to earthquakes.”…

Events that came from outside the blogosphere also seemed to exhibit aftershocks that line up with Omori’s law for the frequency of earthquake aftershocks.

“We show that the public reception of news reports follow a similar statistic as earthquakes do,” the researchers conclude. “One might also think of a ‘Richter scale’ for media events.”

“I always think it’s interesting when people exploit the scale of online media to try to understand human behavior,” said Duncan Watts, a researcher at Yahoo! Research who describes himself as a “reformed physicist who has become a sociologist.”

But he notes that drawing mathematical analogies between unrelated phenomena doesn’t mean there’s any deeper connection. A lot of systems, including views on YouTube, activity on Facebook, number of tweets on Twitter, avalanches, forest fires, power outages and hurricanes all show frequency graphs similar to earthquakes.

“But they’re all generated by different processes,” Watts said. “To suggest that the same mechanism is at work here is kind of absurd. It sort of can’t be true.”

A couple of things are of note:

1. One of the advantages of the Internet as a medium is that people can fairly easily track these sorts of social phenomenon. The data is often in front of our eyes and once collected and put into a spreadsheet or data program is like any other dataset.

2. An interesting quote from the story: the “reformed physicist who has become a sociologist.” This pattern that looks similar to an earthquake is interesting. But sociologists would also want to know why this is the case and what factors affect the initial “wordquake” and subsequent aftershocks. (But it is interesting that the paper was developed by physicists: how many sociologists would look at this word frequency data and think of an earthquake pattern?)

2a. Just thinking about these word frequencies, how does this earthquake model differ from other options for looking at this sort of data? For example, researchers have used diffusion models to examine the spread of riots. Is a diffusion model better than an earthquake model for this phenomena?

3. Does this model offer any predictive power? That is, does it give us any insights into what words may set off “wordquakes” in the future?

Risk of California superstorm – and what should be done about it?

Human beings have a remarkable capacity to build settlements in harsh conditions. Recently, I have wondered what would possess settlers in the 1800s to live in the Upper Midwest with its harsh winters. A classic example of a place with both advantages and disadvantages: California. On one hand, a temperate to warm climate with a wonderful range of habitats (mountains to coast) and rich farmland in the middle of the state.

And yet, California has a number of natural threats. The latest: scientists predicting a superstorm that could flood the state for an extended period.

A group of more than 100 scientists and experts say in a new report that California faces the risk of a massive “superstorm” that could flood a quarter of the state’s homes and cause $300 billion to $400 billion in damage. Researchers point out that the potential scale of destruction in this storm scenario is four or five times the amount of damage that could be wrought by a major earthquake…

The threat of a cataclysmic California storm has been dormant for the past 150 years. Geological Survey director Marcia K. McNutt told the New York Times that a 300-mile stretch of the Central Valley was inundated from 1861-62. The floods were so bad that the state capital had to be moved to San Francisco, and Governor Leland Stanford had to take a rowboat to his own inauguration, the report notes. Even larger storms happened in past centuries, over the dates 212, 440, 603, 1029, 1418, and 1605, according to geological evidence…

The scientists built a model that showed a storm could last for more than 40 days and dump 10 feet of water on the state. The storm would be goaded on by an “atmospheric river” that would move water “at the same rate as 50 Mississippis discharging water into the Gulf of Mexico,” according to the AP. Winds could reach 125 miles per hour, and landslides could compound the damage, the report notes.

Such a superstorm is hypothetical but not improbable, climate researchers warn. “We think this event happens once every 100 or 200 years or so, which puts it in the same category as our big San Andreas earthquakes,” Geological Survey scientist Lucy Jones said in a press release.

If this is a real possibility, the question then becomes what the state should do about it. It is another example of weighting risks: should the state implement all sorts of rules and plans to limit the possible damage or should they simply go on with life and deal with the consequences when they come? Of course, California isn’t the only place that faces such questions: hurricanes pose a similar threat on the East or Gulf Coasts and many communities have homes or businesses built on flood plains.

Regardless of what California does with this information, perhaps this can become additional fodder for disaster movies. I can see the plot line now: California is hit with a major storm followed by a major earthquake with both accompanied with major mudslides followed by our set of heroes running for the hills…you’ve seen this plot line before. But this flood of 1861-1862 does sound intriguing – perhaps more information about this past event would help current officials plan for future events.