Tsunami generation process of mega-quakes revealed by atmospheric pressure wave analyses

2014 Fiscal Year Final Research Report

• Project/Area Number: 24654144
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics
• Research Institution: The University of Tokyo
• Principal Investigator: WATADA Shingo 東京大学, 地震研究所, 助教 (30301112)
• Co-Investigator(Renkei-kenkyūsha): IMANISHI Yuichi 東京大学, 地震研究所, 准教授 (30260516)
• Research Collaborator: MURAYAMA Takahiko ; ARAI Nobuo ; IWAKUNI Makiko ; NOGAMI Maki
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 津波 / 2011年太平洋東北沖地震 / 2010年チリ地震 / 津波伝播速度低下伝播速度低下 / 初期反転位相 / 津波シミュレーションシミュレーション / 遠地津波波形 / DART

Outline of Final Research Achievements

Tsunami traveltime delays up to 15 min relative to the simulated long waves from the 2010 Chilean and 2011 Tohoku-Oki earthquakes were observed. Small negative phases before the main peak were found at distant locations. Measured tsunami phase velocities show reverse dispersions at periods beyond 1000 s and are consistent with a tsunami mode coupled with a self-gravitating elastic Earth, suggesting that the effects of compressible seawater, elastic sea-bottom deformation, and gravity variations during tsunami propagation are responsible for the traveltime delays and the initial negative phases. A new method to simulate tsunami waveforms on real ocean bathymetry that takes into account the three effects was developed. The simulated waveforms reproduce the observed waveforms, including a small negative phase at distant locations. The traveltime difference between the observed and simulated waveforms has decreased to less than 5 min and the waveform difference remarkably diminishes.

Free Research Field

固体地球物理学