Desktop seismology: How a maker-inspired device is changing seismic monitoring

by Sarah Derouin
Wednesday, November 8, 2017

Earth groans and shimmies constantly, producing everything from occasional building-collapsing earthquakes to subtle shaking humans don’t even feel. There are many ways to track this shaking, ranging from sensitive, expensive seismograph stations to various citizen-science approaches, including the U.S. Geological Survey’s “Did You Feel It?” program, through which people can report what they felt during an earthquake using an online survey.

On the more expensive side of things, professional-grade seismographs require substantial funding to purchase as well as the scientific know-how to install, monitor and analyze the constant rumblings they pick up. (“Seismograph” and “seismometer” are often used interchangeably, but they actually refer to different things: a seismometer is the sensor that detects an earthquake, while a seismograph is the whole unit, including the means to transmit the shaking data.) The sensor packages — which pick up Earth’s vibrations — within seismographs typically range in size from a soda can to a basketball, depending on the measurement precision for the instrument. Costs for high-grade seismographs and installations start around $5,000 and can easily exceed $100,000. Complicated operation, and the software needed to run it, can also deter even the most curious amateurs who want to maintain their own sensitive seismic monitoring.

Enter a novel personal seismograph: the Raspberry Shake. Named after the computer that powers the instrument (the Raspberry Pi), the Shake was invented in 2016 by a hobbyist. “I got into [seismometers] as a hobby in the late ‘90s, and I always wanted to make something for home use and for school use,” says Ángel Rodríguez, founder of OSOP, a geophysical instrument company that manufactures the Raspberry Shake as well as seismographs for professional use.

Rodríguez, who has a degree in oceanography, taught himself the science behind geophysical instrumentation and says that through that process, “you can’t help but pick up some seismology.” He is a self-described “maker” who set out to develop a small, affordable seismograph for hobbyists who were curious about earthquakes and seismic shaking. He and his team at OSOP quickly learned that interest in personal seismographs reached beyond the backyard seismologist. The Shake is also a way to supplement the coverage of professional seismic instruments with low-cost equipment — something seismologists call densifying — and it captured the attention of state and federal agencies in the United States and elsewhere around the world. It turns out that a seismograph smaller than a box of tissues has become a very useful tool for scientists and educators alike.

Developing the Shake

The Raspberry Shake is a desktop seismograph suitable for the earthquake-curious or the seismologist on a budget. Each Shake costs between $100 and $1,200 — depending on whether optional features are included — and consists of a seismometer and the electronics needed to collect and transfer data to the user, all of which is mounted on a small circuit board. The sensor, called a geophone, is about the size of your thumb; it is essentially a magnet suspended on a string that is wrapped with a coiled wire. “You can imagine: Earth starts moving and the magnet starts going up and down with the motion; that generates small voltages in the coil running around it — that is the output,” says Branden Christensen, director of OSOP and the Raspberry Shake Project.

This electrical output is then processed by a tiny computer that powers the unit, resulting in the same sorts of spiky data plots commonly produced by high-grade seismographs. When encased in a custom plastic box, the whole unit is still smaller than a child’s lunchbox.

Development of the Shake emerged from a combination of curiosity and timely technology advances. About 10 years ago, Rodríguez put his geophysics-focused hobby into action and formed OSOP, which was originally headquartered in his house. With a second employee added, the company moved into Rodríguez’s garage. And as new team members were hired, the company expanded out of the garage, eventually settling into an office in Volcán, Panama.

Until about five years ago, OSOP only sold professional-grade seismographs made by other companies, including expensive broadband instruments that can detect earthquakes on the opposite side of the world. Eventually, the OSOP team decided to create its own product, focusing on providing quality instruments for local and regional seismic monitoring that were more affordable than broadband systems. “We were changing to a company that had our own solutions and filled a niche in the market that wasn’t being adequately served,” Christensen says.

The company first developed multiple versions of sophisticated, short-period instruments, ideal for detecting seismic events 10 to 100 kilometers away. They are less expensive than high-end broadband instruments: A short-period seismograph can be purchased for about $5,000 versus $50,000 or more for a broadband.

As OSOP developed the technology for its regional-monitoring seismographs, the company stumbled on an unexpected surprise: The same hardware and software developed for short-period instruments was translatable to a personal seismograph, Rodríguez says. “Once the whole thing had been developed, it was very easy … to make a sensor that was not quite professional grade but that generated data in a format that professionals could use,” and was suitable for monitoring regional earthquakes.

The last step in developing the Shake was to figure out how best to connect the circuit board and geophone to a computer, while keeping the whole unit small and affordable, and avoiding the need for a cumbersome desktop setup. Rodríguez and Christensen chose the compact and powerful Raspberry Pi — about the size of a credit card — to pair with the Shake. Since 2012, the Raspberry Pi Foundation has been selling small, single-board computers for about $35. Originally marketed to schools and developing countries as an inexpensive way to get high-quality computers to interested users, it also gained popularity in the maker community.

The power and ubiquity of the tiny Raspberry Pi didn’t go unnoticed by the Shake team. “The reason I chose Raspberry Pi for the project was because the Raspberry Pi Foundation has sold 11 million of them,” Rodríguez says. With so many out there, OSOP wanted to piggyback on the computer’s popularity with a do-it-yourself approach, he says. “I was hoping that people would buy a little card and a geophone [from us], and would build their own seismograph” using their Raspberry Pis, Rodríguez says. It seems that approach worked.

Growing Pains

Once OSOP developed the Shake, scaling up production required financial backing. So the company turned to an approach that has become common among science gadget companies: crowdfunding. The team launched a Kickstarter campaign in 2016, in part to gauge interest, but also to fund an initial production run. More than 500 backers from 50 countries supported the campaign, and Raspberry Shakes started shipping in late November 2016. Different packages featuring various options are available for purchase, including one that includes a Raspberry Pi computer. In true hobbyist fashion, the most popular product unit from the first campaign was the Magnitude 8.0 version, which requires some user assembly and a user’s own Pi.

The company’s success on Kickstarter was both exciting and exhausting, Christensen says. In a few short months, the Shake team had to build the units and put all the software, user manuals, cloud services and mobile apps together. There have “been a lot of long nights,” Christensen says, along with a few growing pains.

The Shakes are made by OSOP in Panama. Production and the creation of hardware and software went relatively smoothly, considering it was a big diversion from their normal business. “There’s been a lot to learn in the process — we used to make 10 [instruments], maximum 100 at a time, for our geophysical clients, and suddenly we had to make 600 and plan for sales upward of 1,000,” Christensen says. The biggest challenge turned out to be when OSOP tried to ship to customers using a new government-run postal service — about 15 percent of packages were lost. “It was a big punch in the gut. It’s around Christmas and you realize that these [Shakes] are never going to show up,” he says. He said they reshipped to clients after December, but that 15 percent of the Raspberry Shakes were lost and that money was never recovered.

Since the initial shipping snafu, the government postal system’s “kinks have been ironed out,” Christensen says. The Raspberry Shake is a full part of OSOP’s business now, alongside their professional-grade seismometers. Interested users can browse through the different Shake packages on their website (www.raspberryshake.org).

Putting Shakes to Use

Low-cost, small seismographs that can be used for both personal and research endeavors aren’t totally new. “The first project that was really groundbreaking [in low-cost seismic monitoring] was called the Quake-Catcher Network,” says Susan Hough, a geophysicist at the U.S. Geological Survey in Pasadena, Calif. The Quake-Catcher Network, or QCN, was created by researchers at Stanford and the University of California, Riverside, and is still in operation today. The QCN relied on sensors that were plugged into a desktop or laptop computer that would record ground motions at that location. “Raspberry Shake is building on work that goes back at least a decade, capitalizing on these low-cost emerging technologies developed for commercial applications. The Raspberry Shake is a step up the evolutionary ladder,” Hough says.

The plug-and-play nature of the Shake appeals to hobbyists and scientists alike. “You basically plug it into an ethernet port and you’re a couple of minutes away from getting a live monitoring station in your house or office,” says Jefferson Chang, geophysical operations manager for the Oklahoma Geological Survey. He originally bought one unit to try out, and liked it so much that he purchased 100 units for the state.

It’s also useful for students. The instrument’s simple setup, the easy-to-understand software and the online manual were all carefully designed to be useable by a variety of user groups, Rodríguez says. Any shaking, whether from an earthquake or a heavy-footed upstairs neighbor, can be seen in real time on an attached monitor. A video on the Raspberry Shake website shows Rodríguez dropping various items on a table where a unit sits: The impacts show up almost instantly on graphical displays that would grab students' attention. The Shake’s see-through case and rapid feedback make it perfect for the classroom, Rodríguez says.

Chang agrees; he decided to incorporate the Raspberry Shake as part of his outreach initiative for teachers around Oklahoma. His idea is to start with a handful of “pioneer teachers,” giving them each a Raspberry Shake for their classroom. Chang says these teachers are in charge of creating curricula based around the instrument, as well as teaching fellow educators about its use through a workshop. He envisions that the program will be free to Oklahoma teachers, with the goal of giving everybody their own seismograph so they can do citizen science in their classrooms and, ideally, engage students in earth science. Teachers using the Shake in their classroom can pose questions to their students about earthquakes and other shaking, asking for example, “Hey, what did that school see in western Oklahoma versus eastern Oklahoma?” Chang notes. An online network allows students to look up and visualize the answer for themselves.

Shake users, called “Shakers,” have the option to keep data from their units private or to join the network of Shake seismographs around the world. If they connect to the network, their seismic data can be seen by anyone, simply by clicking on the station-view map to see ground motions around the planet. Users can join an online discussion forum and communicate through Google groups to troubleshoot problems, share earthquake measurements and crowdsource answers to questions. Christensen says the forum is extremely active, with users taking the initiative to run their own quality-control checks on hardware and software, or simply “helping other geeks to get their Raspberry Shakes up and running.”

As of mid-August, there were more than 1,000 Raspberry Shake owners worldwide, with about 360 Shakes online, though the latter number fluctuates over time. Shakers tend to go on- and offline on a regular basis, Christensen notes. He recalls noticing one station that kept popping up on the network in different locations in multiple countries. Puzzled about this roaming unit, he contacted its owner, who, it turned out, had taken his Shake along with him on vacation to Mexico and Costa Rica.

Professional Use

Although the Shake was initially developed for hobbyists, Rodríguez and Christensen say they hope professionals will be able to use it to increase the density of seismic networks around the world. Helping monitor subtle shaking and local seismic activity was a goal from the beginning, Rodríguez says. “If you have a little earthquake, say magnitude 2.5 or 3, the energy from that earthquake only travels a couple hundred kilometers at best. If your station density has a 100-kilometer hole in it, you [may] not even see that event, no matter how good your instruments are,” Rodríguez says. Adding inexpensive sensors between sensitive broadband stations increases coverage and allows networks to detect more information for smaller events. “You can get [high] station density,” he says. “For the price of a single installed broadband, you could get hundreds of Raspberry Shakes.”

In Oklahoma, where the occurrence of frequent earthquakes is a relatively new development, understanding how Earth shakes can help people feel less nervous, Chang says. “Most Oklahomans didn’t experience earthquakes before six to seven years ago,” he says. “And the first things that they think of are … buildings falling down and freeways going crazy; that’s the vision they have in their head because that’s what they see in movies.” Oklahoma’s earthquakes are usually fairly low to moderate magnitude — typically ranging from magnitude 3 to about magnitude 6 — but experiencing seismic shaking can still be an unsettling experience for residents. Having small-scale seismographs on hand allows scientists like Chang to allay fears by showing that dozens of earthquakes — most of which no one feels — happen every day in the state.

Chang says he received more than 100 phone calls in 2016 from Oklahoma residents who thought they felt shaking and were hoping to have a seismograph installed at their homes. High-end instruments are cost-prohibitive for such home use, he says, “but for the citizens who just want to know if their house is shaking, or if there was an earthquake, [Raspberry Shake] is perfect.”

Finding a Niche

Collecting global earthquake data with personal seismographs can sound too good to be true, and in some cases it is, because the Raspberry Shake is designed to only detect a certain set of seismic waves. When a big earthquake occurs, Hough says, “Earth is ringing like a bell — you can think of the earthquake [waves] as musical tones: A big earthquake releases very low tones” that travel all the way around the planet, she says. But the Shake doesn’t always detect those types of distant, low-frequency waves from far-flung places, although Christensen says that many Shakes around the world did detect the September 2017 magnitude 8.1 earthquake in Mexico.

Instead, the Shake really shines when detecting high-frequency seismic waves (between about 0.1 and 25 Hertz) released from earthquakes that are nearby; high-frequency waves dissipate in Earth’s interior over shorter distances than low-frequency waves. “We’ve created an instrument that’s fine-tuned just to look at local and regional events, 10 to 100 kilometers away,” Christensen says.

The instruments have other limitations as well, some of which were purposeful on the part of the OSOP team to keep the Shake easy to use and inexpensive. For example, the Shake samples data 50 times per second, whereas expensive, professional-grade seismographs can sample data more often. The sampling rate impacts a seismograph’s ability to resolve seismic waves — higher rates offer greater detail and allow higher-frequency waves to be captured more accurately. Imagine a sinuous wave of energy passing through the seismometer, Christensen says: Taking 100 snapshots, or samples, of the wave each second would give you a better feeling for its actual shape and size versus, say, only taking 10 snapshots per second. Sampling at 50 times per second offers a happy medium, he says.

ome limitations of the Raspberry Shake have been raised by users. Amid the interest in the Shake at the American Geophysical Union meeting in San Francisco last December, Christensen says many users expressed a desire to equip their Shakes with accelerometers capable of monitoring strong shaking. The detection ability of the Raspberry Shake’s geophone saturates, or maxes out, during strong shaking events, often limiting measurements of earthquakes above about magnitude 5 (this can vary depending upon the Shake’s distance from an earthquake source and the magnitude of the event, as well as geology).

The OSOP team heard the concerns and created an updated version: the Raspberry Shake 4D. Mimicking the success of their first Kickstarter effort, they created a new campaign, eventually exceeding their funding goal by almost 1,200 percent. “If you’re just doing home seismology, the original Raspberry Shake is perfect for you,” Christensen says. But to be part of the professional seismic monitoring community, and to contribute data to shake maps, for example, you need the sort of acceleration data provided by the 4D.

Christensen says that the relatively small number of seismic stations around the world has been a limiting factor in seismic studies, but the availability of inexpensive sensors can fill in gaps and provide more information to scientists globally. “We’re looking at situations where we could go from dozens and hundreds of [stations in different networks around the world] to thousands,” he says. Geophysical institutions are looking carefully at including the Shake 4D in their networks, Rodríguez adds. Professional earthquake scientists, “better than anyone, know that densification [of networks] cannot happen at $50,000 per installation.”

Hough, for one, has firsthand experience trying to increase seismic monitoring coverage in Myanmar. “I’ve been working since 2012 to create a seismic network in Myanmar, and after five years, we have upgraded five stations in the ground to anchor a state-of-the-art network,” Hough says. “It’s just tough,” because of the cost and expertise needed to install high-end stations, she says. Her team has recently installed two Shakes in Myanmar as part of a pilot study of their effectiveness. “We’re looking at the [Shake] data and comparing it to the nearby state-of-the-art station, and seeing how they perform.” If the results are encouraging, she says, they may try to install additional Shakes to densify monitoring coverage in the country.

Seismic monitoring technology has always been highly specialized, Hough says. And she says that although these low-cost seismographs aren’t going to replace high-end “Cadillac” instruments, their research potential is exciting. “It’s a whole different approach to monitoring, and I think we’re just seeing the tip of the iceberg in terms of what [the Shake] will be able to do. I think seismic monitoring 25 years from now could look different than it does now.”