Science Gazette

Monitoring crustal deformation using mobile phone GNSS networks


Japanese Earth Science researchers examined the potential of a dense Global Navigation Satellite System (GNSS) network, which is installed at cell phone base stations, to monitor crustal deformation as an early warning indicator of seismic activity in a paper published February 9 in Earth Planets and Space. The findings shown that data from a mobile phone network may approach the accuracy of data from a government-run GNSS network, while also offering more comprehensive geographic coverage.

Crustal deformation is measured around plate borders, active faults, and volcanoes to determine the buildup of stresses that might cause major seismic events. GNSS networks have been built all over the globe in places prone to volcanoes and earthquakes, such as Hawai’i, California, and Japan. These networks’ data may be evaluated in real time to help with tsunami forecasting and earthquake early warning systems.

The Geospatial Information Authority of Japan manages Japan’s GNSS network (GEONET). While GEONET has been useful in earth science research, its average distance between stations of 20-25 kilometers hinders monitoring of crustal deformation in certain places. Magnitude 6-7 earthquakes on active faults in rural Japan, for example, with fault lengths of 20-40 kilometers; GEONET site spacing is significantly inadequate to quantify their deformation with sufficient accuracy for use in prediction models.

Japanese mobile phone providers, on the other hand, have built GNSS networks to increase locational information for applications such as automatic driving. The latest research looks into the ability of a GNSS network established by the carrier SoftBank Corporation to detect crustal deformation. This commercial enterprise manages 3300 locations in Japan, which is 2.5 times the number of sites managed by the government GEONET system.

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“By leveraging these observation networks, we want to comprehend crustal deformation processes at a better resolution and to seek for previously undiscovered occurrences,” said research author Yusaku Ohta, a geoscientist and assistant professor at Tohoku University’s Graduate School of Science.

The research evaluated the quality of SoftBank GNSS data from cell phone base stations by using raw data given by SoftBank GNSS from cell phone base stations. Two datasets were analyzed: one from a seismically calm nine-day period in September 2020 in Japan’s Miyagi Prefecture, and the other from a nine-day period that includes a 7.3 magnitude earthquake off the coast of Fukushima Prefecture on February 13, 2021.

The researchers discovered that SoftBank’s extensive GNSS network can monitor crustal deformation with acceptable accuracy. “We have demonstrated that the original, very dense GNSS observation networks of cell phone carriers that are being deployed for the advancement of location-based services can monitor crustal deformation with unprecedentedly high spatial resolution,” said earth scientist Mako Ohzono, associate professor at Hokkaido University.

In the future, they believe that integrating the SoftBank sites with the government-run GEONET sites will result in improved spatial resolution data for a more complete fault model. Combining the networks in the Fukushima Prefecture would result in an average density of GNSS stations of one per 5.7 kilometers. “It suggests that these private sector GNSS observation networks might complement GNSS networks managed by governmental entities,” Ohta added.

The study cleared the path for researchers in Japan and abroad to investigate the synergy of public and commercial GNSS networks as a resource for seismic monitoring. “The findings are critical for understanding earthquake events and volcanic activity, which may help with catastrophe prevention and mitigation,” Ohzono said.

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