Japan Geoscience Union Meeting 2016

Presentation information


Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS32] Crustal Deformation

Tue. May 24, 2016 9:00 AM - 10:30 AM A05 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Masayuki Murase(Department of Earth and Environmental Sciences, College of Humanities and Sciences, NIHON University), Ryosuke Doke(Hot Springs Research Institute of Kanagawa Prefecture), Chair:Hisashi Suito(Geospatial Information Authority of Japan), Yusaku Ohta(Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University)

9:15 AM - 9:30 AM

[SSS32-14] Surface movements immediately before and after the 2011 Tohoku-oki earthquake from kinematic solution of GNSS and thermal expansion of the pillars

*Yuki Saegusa1, Kosuke Heki1 (1.Department of Natural History Sciences, Graduate School of Science, Hokkaido University)

Keywords:crustal movement, GNSS, thermal expansion

The Tohoku-Oki earthquake (Mw9.0) occurred on March 11, 2011, and fault dislocation at the Japan Trench caused large eastward surface displacement of the Japanese Islands. Ohta et al. (2012) reported displacement of GNSS stations in NE Japan with the time resolution of three hours just before the Tohoku-Oki earthquake. Hino et al. (2014) reported high time-resolution vertical movements of the seafloor close to the epicenter using ocean bottom pressure gauge. Hirose (2011) analyzed the Hi-net tiltmeter data just before the Tohoku-oki earthquake. All these observations showed clear signatures of the afterslip of the foreshock that occurred two days before the main shock, but did not show any anomalous movement immediately before the earthquake.
For time periods just after the earthquake, Munekane (2012) reported kinematic analysis results of GNSS stations in NE Japan, and identified signatures of crustal deformation associated with several large foreshocks and the afterslip of the main shock fault. Mitsui & Heki (2012) analyzed periodic surface movements caused by the Earth's free oscillation. In addition to these “real” crustal movements, Munekane (2012) identified uniform horizontal displacement signatures, and inferred that they originate from differential thermal expansion of GNSS pillars due to direct sunlight.
In our study, we try to investigate spatial and temporal correlation between the sunshine and thermal-expansion origin horizontal displacements (see the attached figure). Here we used the 30-second position data of the GEONET station in NE Japan obtained using the RTnet software package by Dr. T. Iwabuchi, UNAVCO. This is the same data set that Mitsui and Heki (2012) used. We also use the weather data available from the website of Japan Meteorological Agancy (http://www.data.jma.go.jp/risk/obsdl/index.php).
Description about the attached figure
[A]:Position change of the GNSS station ( JST 12:00-13:00 ) by kinematic solution.
[B]:The sunlight hour (JST 12:00-13:00) by AMEDAS.
[C]:Solar Azimuth at every each hour.
R. Hino, D. Inazu, Y. Ohta, Y. Ito, S. Suzuki, T. Iinuma, Y. Osada, M. Kido, H. Fujimoto, Y. Kaneda (2012):Was the 2011 Tohoku-Oki earthquake preceded by aseismic preslip? Examination of seafloor vertical deformation data near the epicenter, Mar Geophys Res (2014), 35, 181–190
Y. Mitsui & K. Heki (2012):Observation of Earth’s free oscillation by dense GPS array: After the 2011 Tohoku megathrust earthquake, SCIENTIFIC REPORTS, 2, 931
H. Munekane (2012):Coseismic and early postseismic slips associated with the 2011 off the Pacific coast of Tohoku Earthquake sequence : EOF analysis of GPS kinematic time series, Earth Planets Space, 64, 1077-1091, 2012
H. Hirose (2011):Tilt records prior to the 2011 off the Pacific coast of Tohoku Earthquake, Earth Planets Space, 63, 655-658, 2011
Y. Ohta, R. Hino, D. Inazu, M. Ohzono, Y. Ito, M. Mishina, T. Iinuma, J. Nakajima, Y. Osada, K. Suzuki, H. Fujimoto, K. Tachibana, T. Demachi, S. Miura (2012):Geodetic constraints on afterslip characteristics following the March 9, 2011, Sanriku-oki earthquake, Japan, Geophysical Research Letters, Vol. 39, L16304