As the world went down in 2020, Raspberry Shakes listened

“It’s the trains! ”Ryan Hollister moved in with his wife Laura when he moved into their home in Turlock California. For two weeks in 2017, they had been looking at data from the newly installed Raspberry Shake, a Raspberry Pi-powered instrument that detects how the earth moves in a particular location. Expecting to see earthquake-story wiggles in the distance, they regularly saw waves in the shape of manure. “The biggest challenge,” says Laura Hollister, “is the sound.”

“I thought it was the flush toilet or the washing machine,” says Ryan Hollister, but simple tests of going to the restroom or doing the laundry proved it wrong. . While in the middle of his car watching the train retreat through Turlock, he realized that the three tracks that cross this small California city could be causing this mysterious seismic sound. As soon as he got home, he pulled up Raspberry Shake data. Certainly, every strange wave of seismic waves corresponded to a train, with the highest waves connecting to the nearest track record, just half a mile from the house.

This was not the last time their seismic hearing aid picked up signs of human activity. As COVID-19 entered our world, the Hollisters, a wife team of earth science educators, noticed that their Raspberry Shake recorded much lower than normal activity levels. The fall was named at times when their street, main artery to the local high school, should have been crowded with teenagers.

That change was far from limited to Turlock. Thomas Lecocq, a seismologist who pays special attention to the ubiquitous vibration of the Earth, saw a dramatic reduction in high-frequency noise on a permanent seismic station. under his sight at the Royal Belgian Observatory. This particular brush was quieter and longer than the one he saw during the controlled days between Christmas and the New Year, and coincided with the closure of his country.

In the months that followed, Lecocq and 76 coauthors from around the world shook through data from seismic stations spanning more than 70 countries using the Python code Lecocq wrote specifically for this purpose. Usable data totaled 268 stations, 185 of which saw high frequency seismic noise falling by up to 50 percent in urban areas. The changes came to a gray scale with the closure of all countries in response to COVID-19. As the symptoms fell from driving, picking up, and even walking away, John Nesbitt, one of the Lecocq coauthors says, “Maybe we can do some research [geologic] signals we had never seen before because he was surrounded by that sound. “

Many of the stations were high-end research instruments installed by university or government scientists. But 65 were tiny Raspberry Shakes, sitting in the homes and offices of scientists and hobbyists alike. It turns out that when people make a lot of noise, talking seismically, anyone with an extra Raspberry Pi and a few hundred dollars for a Raspberry Shake swivel board and some sensors will see it. .

Build your own seismic station

The basic recipe for a seismic station requires four ingredients: sensors to measure Earth’s motion, a way to record the measurements, a long-term storage solution (either local or elsewhere), and a power source, says Emily Wolin, Manager Seismic Network for the US Albuquerque Seismological Laboratory (USGS).

Modern seismic stations boast a number of sensors that detect a wide range of frequencies, capturing the Earth’s motion in three directions – upward, northwest, and north-south. Digitizers and data loggers accurately record and stamp the data. To power the equipment, the most remote stations can use solar panels, with power requirements varying greatly according to communication needs, Wolin said.

To add a new seismic station to an earthquake research network, Wolin says scientists need to study places that take into account regional geology and potential sources of noise – such as railways (no home Hollister never cut). With a list of candidate sites, they then identify and contact landlords for permission, and subsequently gain access to construction, installation and maintenance.

Wolin explains that preparation can sometimes involve “employing a drill string to drill hundreds of meters into hard rock. “In some cases, water and water-sealed seismic cellars need to be carefully constructed to keep equipment so sensitive that they would otherwise cause small changes in pressure and temperature. Cellars also help reduce pesky anthropogenic noise. To install the sensor and electronics, “it’s not rocket science,” says Sue Hough, a USGS physicist, but “she takes special training.”

Each level of complexity adds another line to the bill. According to Hough, high-end versions of a seismic station can cost more than $ 10,000, excluding installation costs. Branden Christensen, CEO of Raspberry Shake, says that when these costs are included, the installation of a single seismic station could cost more than $ 100,000. These prices are just affordable for government agencies, research institutes and business.

Raspberry Shakes, on the other hand, have basic versions of the same parts at a fraction of the price. The Raspberry Shake circuit board costs as little as $ 100, and plugs into almost any ethernet or Raspberry Pi with wireless capability. “We thought people would have that [Raspberry Pis] sitting around in their drawers, ”said Christensen,“ and us [designed Raspberry Shakes to] support them all. “

A seismic sensor, like geophysics, plugs into a Raspberry Shake board, which serves as an amplifier and digitizer. The output of the sensor comes in the form of voltage differences that need to be amplified and converted to a known voltage each speed. This inversion, called gain, leaves a yield in voltage units, according to Nesbitt, who is also a chief scientist at Raspberry Shake.

The Raspberry Shake digitizes this information and pipes it to the Raspberry Pi for further processing and archiving. An 8 gigabyte microSD card, which Nesbitt describes as the Raspberry Pi’s hard drive, ships with all Raspberry Shake, and comes preloaded with all Shake software. The Raspberry Pi has the SD card and powers the entire seismic station. “[The Raspberry Pi] is the computer at the heart of everything, ”says Nesbitt.

With a Raspberry Shake board, building your own seismic station from the ground up becomes as simple as installing a sensor and plugging the Raspberry Pi into your wall socket, though Christensen recommends curbing rotation (you can use Lego bricks!) To protect it from the lumps. of the members of your family.

If you prefer not to collect your own from the very beginning, Raspberry Shake makes several turnkey choices based on the number and type of sensors you want. Turnkey options, Hough says, pack all of those parts in a tight plexiglass box.

The Hollisters chose the turnkey Raspberry Shake 4D, which is available for less than $ 400. To install it, Ryan Hollister says they just had to be, “level it and point the axes in the right direction so that properly steered, and plug it in. “Easy as, well… pi (e).