A Southern California high school junior has developed a low-cost seismometer using parts that total less than $100—a fraction of the cost of a scientific-grade system. She designed her device as a consumer product for widespread adoption in homes.
“It’s small and cheap and accessible,” said Vivien He, a student at Palos Verdes Peninsula High School in Rolling Hills Estates, Calif. In April, she presented her work at the 2021 Annual Meeting of the Seismological Society of America.
Earthquake Early Warning
When an earthquake occurs, it generates compressional (P) waves and shear (S) waves, which emanate from the epicenter through Earth. Sensors that detect P waves can provide a warning before slower—but more destructive—S waves arrive.
“Even with just a few seconds of warning, we can provide a useful alert to people: that they can do something…to protect themselves,” said Angie Chung, a seismologist at the Berkeley Seismological Laboratory in Berkeley, Calif. For instance, someone could duck under a table for protection from falling objects.
Chung works on ShakeAlert, an earthquake early-warning system on the U.S. West Coast that includes a network of seismic monitoring stations. The system launched in California in October 2019 and expanded to include the Pacific Northwest in the spring of 2021. After sensors detect seismic activity, data are sent to processing centers that determine the earthquake’s magnitude and the affected area. Seconds later, people receive wireless emergency alerts or notifications in the MyShake app.
ShakeAlert is a boon for public safety—but it comes at a cost. According to a 2018 report, the system’s infrastructure and sensor networks will run an estimated $39.4 million. There are cheaper alternatives, however. Chung previously worked on the Quake-Catcher Network, a research project that uses low-cost accelerometers—or even laptops with built-in accelerometers—to detect earthquakes. Other projects, including the MyShake app, take a similar approach using smartphones.
Engineering in the Time of COVID-19
In addition to seismic waves from natural sources, seismometers typically contend with the rumble of human activities, like traffic and sporting events. Because of COVID-19 lockdown measures, seismic noise quieted down by a median average of 50% worldwide. After learning about this global hush, He was intrigued.
“Since I was at home, I wondered if I could measure it myself,” she said. With the help of Internet searches, He threw herself into the project, reading papers about earthquake detection and learning how to program in Python. She even taught herself to solder, using a bathroom as her laboratory.
“The lighting is really good,” He said.
The earthquake sensing element of her device is a geophone, a component that converts ground motion into electrical signals. An analog-to-digital converter digitizes these signals, and a Raspberry Pi computer handles additional processing. Python programs perform analysis, activate an onboard alarm when they detect an earthquake, and even send out text alerts to friends and family.
The night that He finished writing code to chart the geophone data was right before an earthquake occurred in Southern California. When she woke up in the morning, she found that not only had her device captured the earthquake, but the waveform perfectly matched the data from a U.S. Geological Survey station 4 kilometers from her home. Since September, her device has captured all earthquakes greater than M3.0 in the area.
The device has gone through several rounds of redesign. For the latest version, He designed and laser cut an acrylic case that stacked all the components of her device in an arrangement roughly the size of a Rubik’s Cube.
It was impressive “to see what a high schooler can do with available technology and Google,” said Chung, who moderated the oral session where He presented her work.
In the future, He hopes to extend her earthquake monitoring system to include multiple devices that communicate with each other and provide alerts over a larger area. She also wants to implement machine learning algorithms to ensure that her system identifies true earthquakes. Additionally, He started a nonprofit organization, Melior Earth, to tackle a range of environmental issues, including natural disaster prevention. She hopes to distribute her devices to areas highly impacted by earthquakes.
Overall, she hopes to share her newfound passion for Earth science. “It was really exciting for me,” He said. “I think a lot of other people would be really interested in it, to see the live charting and understand how we detect earthquakes.”
—Jack Lee (@jackjlee), Science Writer