Using cell phone GNSS Networks to monitor crustal deformation

Date:
March 10, 2022
Source:
Tohoku University
Summary:
The Global Navigation Satellite System associated with a Japanese
cell phone carrier can enhance monitoring of crustal deformation
changes for earthquake early warning models.



FULL STORY ==========================================================================
A paper published February 9 in Earth Planets and Space by Japanese Earth Science researchers analyzed 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. The results showed that data from a cell phone network
can rival the precision of data from a government-run GNSS network,
while providing more complete geographic coverage.


========================================================================== Crustal deformation is monitored around plate boundaries, active
faults, and volcanoes to assess the accumulation of strains that lead
to significant seismic events. GNSS networks have been constructed
worldwide in areas that are vulnerable to volcanoes and earthquakes,
such as in Hawai'i, California, and Japan. Data from these networks can
be analyzed in real time to serve in tsunami forecasting and earthquake
early warning systems.

Japan's GNSS network (GEONET) is operated by the Geospatial Information Authority of Japan. While GEONET has been fundamental in earth science research, its layout of 20-25 kilometers on average between sites limits monitoring of crustal deformation for some areas. For example, magnitude
6- 7 earthquakes on active faults in inland Japan have fault lengths of
20-40 kilometers; the GEONET site spacing is slightly insufficient to
measure their deformation with suitable precision for use in predictive
models.

However, Japanese cell phone carriers have constructed GNSS networks to
improve locational information for purposes like automated driving. The
new study examines the potential of a GNSS network built by the
carrier SoftBank Corporation to play a role in monitoring crustal
deformation. With 3300 sites in Japan, this private company oversees
2.5 times the number of sites as the government GEONET system.

"By utilizing these observation networks, we aim to understand crustal deformation phenomena in higher resolution and to search for unknown
phenomena that have not been found so far," explained study author Yusaku
Ohta, a geoscientist and assistant professor at the Graduate School of
Science, Tohoku University.

The study used raw data provided by SoftBank GNSS from cell phone base
stations to evaluate its quality in monitoring crustal deformation. Two datasets were analyzed, one from a seismically quiet nine-day period in September of 2020 in Japan's Miyagi Prefecture, the other from a nine-day period that included a 7.3 magnitude earthquake off the Fukushima coast
on February 13, 2021, in Fukushima Prefecture.

The study authors found that SoftBank's dense GNSS network can
monitor crustal deformation with reasonable precision. "We have shown
that crustal deformation can be monitored with an unprecedentedly high
spatial resolution by the original, very dense GNSS observation networks
of cell phone carriers that are being deployed for the advancement of location-based services," said earth scientist Mako Ohzono, associate
professor at Hokkaido University.

Looking ahead, they project that combining the SoftBank sites with the government-run GEONET sites could yield better spatial resolution results
for a more detailed fault model. In the study area of the Fukushima
Prefecture, combining the networks would result in an average density of
GNSS sites of one per 5.7 kilometers. "It indicates that these private
sector GNSS observation networks can play a complementary role to GNSS
networks operated by public organizations," said Ohta.

The study paved the way for considering synergy between public and
private GNSS networks as a resource for seismic monitoring in Japan
and elsewhere. "The results are important for understanding earthquake phenomena and volcanic activity, which can contribute to disaster
prevention and mitigation," noted Ohzono.


========================================================================== Story Source: Materials provided by Tohoku_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Yusaku Ohta, Mako Ohzono. Potential for crustal deformation
monitoring
using a dense cell phone carrier Global Navigation Satellite
System network. Earth, Planets and Space, 2022; 74 (1) DOI:
10.1186/s40623-022- 01585-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220310115140.htm

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