[S-GD01] Crustal Deformation

[SGD01-P08] An Apparent Reduction of Crustal Activity before the Great East Japan Earthquake (part2)

*Yasushi Harada¹, Asuka Fujita¹ (1.School of Marine Science and Technology, Tokai University)

Keywords:GEONET, The Great East Japan Earthquake, Reduction of Crustal Activity

We compared F3 and new F5 solutions of GEONET(GSI) from 2000 to 2021, and calculated displacement vectors of about 1300 GNSS sites for examining the crustal activity of Japan. First we calculated 30 days running means and standard deviations for the 3-components of F3 and F5 solutions and produced the displacement vectors for 30 days term, and created the animations of the displacement vectors for all GEONET sites from 2000 to 2021. We noted large differences of the positions and the displacement vectors between F3 and F5 solutions. Those differences were largely disappeared after we calculated displacement vectors with center-of-mass-system of coordinates. We also calculated the sum of the lengths of each displacement vectors to investigate overall amount of crustal activity of Japan. The 10 years term decreasing trends of the crustal activity are noted both before and after the Great East Japan Earthquake. It is natural that the decreasing trend appeared after the earthquake, but we found a decreasing trend for the crustal deformation of whole Japan even before the great earthquake. Those decreasing trends are noted both in F3 and F5 solution, and those are even more significant if the trends are produced in the center-of-mass-system of coordinates (See lower figure).