Abstract
Monitoring of crustal deformation provides essential information for seismology and volcanology. For such earth science fields and other purposes, various Global Navigation Satellite System (GNSS) networks have been constructed at the national and regional levels. In Japan, the continuous nationwide GNSS network, the GNSS Earth Observation Network System (GEONET), is operated by the Geospatial Information Authority of Japan. Although GEONET has made a substantial contribution to earth science research, the large spacing of GEONET sites makes it difficult to accurately understand crustal deformation phenomena in some cases. However, cell phone carriers in Japan have constructed independent GNSS networks to improve their positioning services in recent years. In this study, we examine the performance of a GNSS network operated by SoftBank Corp. for crustal deformation monitoring. The network has more than 3300 sites throughout Japan, which is approximately 2.5 times the number of the GEONET sites. To assess the quality of SoftBank's GNSS data, we first analyzed data from Miyagi Prefecture and evaluated the stability of the coordinate time series for nine consecutive days during a quiet (interseismic) period. The calculated standard deviations were approximately the same for both networks. Furthermore, we calculated the displacement between September 2020 and March 2021. The results reveal that almost all SoftBank sites showed a consistent displacement with their surrounding GEONET sites. Next, we analyzed the coseismic deformation associated with the off-Fukushima earthquake (MJMA 7.3) on February 13, 2021, in both static and kinematic modes. We obtained a westward coherent displacement along the coastline in both networks, although several outliers were observed for the SoftBank sites. Based on these initial assessments, we conclude that these private sector GNSS sites are useful for crustal deformation monitoring with appropriate data quality control.Graphical
Highlights
Monitoring of crustal deformation is crucial for understanding the status of strain accumulation in areas around a plate boundary, active faults, and volcanoes.The Global Navigation Satellite System (GNSS) is widely used to capture crustal deformation with a high temporal resolution
The second dataset covered a coseismic period of the offFukushima earthquake (MJMA 7.3) that occurred on February 13, 2021
Evaluation of detectability of coseismic displacement To examine the performance of the SoftBank network in monitoring coseismic deformation, we chose the offFukushima earthquake (MJMA 7.3) that occurred on February 13, 2021, at 14:07:50.5 (UTC) and was one of the most significant events after the installation of the SoftBank network
Summary
Monitoring of crustal deformation is crucial for understanding the status of strain accumulation in areas around a plate boundary, active faults, and volcanoes. The Global Navigation Satellite System (GNSS) is widely used to capture crustal deformation with a high temporal resolution. Over the past several decades, many GNSS networks have been constructed. Regional networks have been established in the United States, which mainly cover seismically and volcanically active areas such as the San Andreas fault system, Aleutian Arc, the Island of Hawai’i, and Yellowstone (e.g., Murray et al 2019). The station distribution reflects the purpose of these networks to monitor deformation at the regional. A part of the data from these networks is analyzed in real time and used for earthquake early warning (EEW) (e.g., Murray et al 2018; Allen and Melgar 2019)
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