Last Update 05/31 2018
The Earth system is a dynamically coupled system composed of the ionosphere, atmosphere, ocean, and solid earth (mantle and core) bound by the elastic, gravitational, Coriolis, and elestro-magnetic forces. We study various geophysical phenomena such as Earth/crustal deformation, gravity change, ionospheric disturbance, seismic waves, atmospheric waves (acoustic and gravity ones), tsunamis, ocean tides to understand the mechanisms of multi-sphere interactions, including not limited to, during earthquakes and volcanic eruptions. We aim at discovering and comprehensively understanding those new geophysical phenomena. We discovered the mechanisms for example (1) Atmospheric pressure change associated with a M8 class earthquake in Japan and modeling the relationship between the ground motion and atmospheric pressure change. (2) Acoustic resonant oscillations between the atmosphere and the solid Earth during major volcanic eruptions. (3) Traveltime delay and initial phase reversal of trans-oceanic tsunamis. Our new research targets are (4) Tsunamis without tsunami sources: Retrieval of tsunamis by the interferometry of deep ocean pressure records. (5) Atmospheric waves and ionospheric disturbance excited by earthquakes and volcanic eruptions. (6) ... and many more studies on multi-sphere interactions.
Watada, S., T. Kunugi, K. Hirata, H. Sugioka, K. Nishida, S. Sekiguchi, J. Oikawa, Y. Tsuji, H. Kanamori, Atmospheric pressure change associated with the 2003 Tokachi-Oki earthquake, Geophys. Res. Lett., 33, L24306, doi:10.1029/2006GL027967, , 2006.
Kawakatsu, H., S. Watada, Seismic evidence for deep water transportation in the mantle, Science, 316, 5380, 1468--1471, 2007.
Rosat, S., S. Watada and T. Sato, Geographical variations of the 0S0 normal mode amplitude: predictions and observations after the Sumatra-Andaman earthquake, Earth Planets Space, 59, 4, 307--311, 2007.
Watada S., Radiation of acoustic and gravity waves and propagation of boundary waves in the stratified fluid from a time-varying bottom boundary, J. Fluid Mech., 627, 361--377, 2009.
Mikumo, T., S. Watada, Acoustic gravity waves from earthquakes, in Infrasound Monitoring for Atmospheric Studies, eds A. Le Pichon, E. Blanc, A. Hauchecorne, Springer, 259--275, 2010.
Watada, S., H. Kanamori, Acoustic resonant oscillations between the atmosphere and the solid earth during the 1991 Mt. Pinatubo eruption, J. Geophys. Res., 115, B12319, doi:10.1029/2010JB007747, , 2010.
Arai, N., M. Iwakuni, S. Watada, Y. Imanishi, T. Murayama and M. Nogami, Atmospheric boundary waves excited by the tsunami generation related to the 2011 great Tohoku-Oki earthquake, Geophys. Res. Lett., 38, L00G18, doi:10.1029/2011GL049146 , , 2011.
Watada, S., Tsunami speed variations in density-stratified compressible global oceans, Geophys. Res. Lett., 40, doi:10.1002/grl.50785, 4001--4006, 2013.
Watada, S., S. Kusumoto, and K. Satake, Traveltime delay and initial phase reversal of distant tsunamis coupled with the self-gravitating elastic Earth, J. Geophys. Res., 119, doi:10.1002/2013JB010841, 4287--4310, 2014.
Yoshimoto, M., S. Watada, Y. Fujii and K. Satake, Source estimate and tsunami forecast from far-field deep-ocean tsunami waveforms – the 27 February 2010 Mw 8.8 Maule earthquake, Geophys. Res. Lett., 43, doi:10.1002/2015GL067181, 659--665, 2016.
Ho T.-C., K. Satake, and S. Watada, Improved Phase Corrections for Transoceanic Tsunami Data in Spatial and Temporal Source Estimation: Application to the 2011 Tohoku Earthquake, J. Geophys. Res., 122, 10, doi:10.1002/2017JB015070, 10155--10175, 2017.