Abstract

The global positioning system (GPS) can be used to monitor the seismic perturbation induced by the 2011 off the Pacific coast of Tohoku Earthquake (magnitude 9.0), Japan, on March 11, 2011, and to trace the tsunami across the Pacific Ocean by measuring the changes in the ionospheric total electron content (TEC). We estimate the vertical and horizontal mean speeds of the seismic and tsunami waves using the time and distance of the TEC perturbation, and then, taking into account those determined speeds, trace back to the epicenter and the tsunami origin by applying a 3-dimensional spherical model. The results show that both the tracked epicenter and the tsunami origin are quite close to the epicenter reported by the USGS, with a mean horizontal propagation speed of 2.3 km/s after the earthquake and about 210 m/s after the tsunami. This consistency confirms that the perturbation sources in the ionosphere are due to the earthquake. This implies that the GPS-TEC measurements have the potential to be part of a lower cost, ground-based, tsunami monitoring system.

Highlights

  • Since the atmospheric density decreases almost exponentially with altitude, energy conservation implies that the pulse amplitude increases upwards as it propagates into the atmosphere (Calais and Minster, 1995)

  • The results show that both the tracked epicenter and the tsunami origin are quite close to the epicenter reported by the U.S Geological Survey (USGS), with a mean horizontal propagation speed of 2.3 km/s after the earthquake and about 210 m/s after the tsunami

  • The U.S Geological Survey (USGS) reported that the origin time of the magnitude 9.0 earthquake was at 05:46:23 UTC; while the epicenter was located at 38.322◦N, 142.369◦E off the east coast of the Tohoku area, Copyright c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB. doi:10.5047/eps.2011.06.024

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Summary

Introduction

Since the atmospheric density decreases almost exponentially with altitude, energy conservation implies that the pulse amplitude increases upwards as it propagates into the atmosphere (Calais and Minster, 1995). We use data from a total of 17 ground-based GPS stations in the GEONET network in Japan, the IGS network and the Taiwan GPS network to detect the ionospheric perturbation induced by the 2011 Tohoku earthquake and the subsequent tsunami, and trace their origins using a 3-dimensional spherical model. 2. Observation of the Earthquake In order to study the ionospheric signature of the earthquake, we process the GPS data from the continuous GEONET in Japan (4 stations designated as 0020, 0047, 0119 and 0232), the IGS (7 stations named ccj, cusv, daej, guam, mizu, pimo and shao) and Taiwan GPS network (2 stations named aknd and alis). 0020#05 0047#26 mizu#05 0232#26 0232#05 0020#09 0047#05 0047#15 0047#18 0020#15 0119#21 ccj2#18 0020#26 daej#26 0119#15 ccj2#26 ccj2#15 ccj2#27 guam#15 aknd#15 aknd#27 shao#15 shao#27 shao#18 alis#15 pimo#15 aknd#18 ccj2#09 cusv#27

Minutes since the earthquake
Hours since the earthquake
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