Gyroscopic Technology Unveils Seismic Insights: Monitoring Volcanoes with Earthquake Eyes

Researchers have developed a prototype fiber optic gyroscope to monitor ground rotations during earthquakes in Campi Flegrei, Naples. This advanced sensor system captures both rotational and linear movements, potentially enhancing risk assessments and early warning systems in this volcanic region.

“During seismic events, the Earth experiences not only linear but also rotational movements,” explained Saverio Avino, lead researcher from the Consiglio Nazionale delle Ricerche Istituto Nazionale di Ottica. “Although rotational movements are typically small and often overlooked, detecting them could provide deeper insights into the Earth’s internal dynamics and seismic sources.”

The new rotational sensor, based on a 2-kilometer-long fiber optic gyroscope, continuously recorded data over five months, successfully detecting noise and ground rotations associated with small to medium local earthquakes. Preliminary observational data from the sensor were published in the journal Applied Optics by the Optica Publishing Group.

Deployment in Naples involves integrating this sensor into an existing network of multiparametric sensors covering the entire city. These sensors monitor various physical and chemical parameters to analyze real-time seismic and volcanic activities.

“Adding ground rotation measurements will expand our understanding of seismic signals from volcanic earthquakes,” noted Danilo Galluzzo from the National Institute of Geophysics and Volcanology. “This additional information will contribute significantly to our comprehensive assessment of volcanic dynamics.”

The gyroscope technology employed is based on the Sagnac effect, where light traveling in opposite directions around a closed loop exhibits varying travel times due to rotation. This effect generates interference patterns in the light that are directly related to the loop’s rotation rate, providing precise angular velocity measurements.

“Our laboratories are strategically located within an active volcanic area, offering a natural laboratory for studying seismic and volcanic phenomena,” Avino added. “Given the frequency of small to medium earthquakes in our area, we can collect extensive data on ground rotations for in-depth analysis.”

To create the prototype gyroscope, researchers utilized standard laboratory instrumentation and optical fiber cables similar to those used in telecommunications. The fiber optic cable was looped to form a continuous path, wound around a 25 cm diameter aluminum spool, and housed in a controlled laboratory environment atop a volcano caldera.

“While the current prototype measures only one directional component of rotational movement, future plans include developing a three-axis gyroscope by combining three such devices,” explained Luigi Santamaria Amato from the Italian Space Agency (ASI). “Improving resolution and stability are our next steps toward establishing a permanent ground rotation observatory in the Campi Flegrei region.”

Reference: “Fiber-optic gyroscope for rotational seismic ground motion monitoring of the Campi Flegrei volcanic area” by Paolo De Natale et al., published in Applied Optics on May 31, 2024.