In-situ and satellite measurements of the 2011 Fukushima Tsunami.

Supervisor: Carlos Garcia-Soto (BEGIK Joint Research Unit IEO-UPV/EHU)
On the 11th of March 2011, a moment magnitude 9.0 Mw earthquake took place near the east coast of Honshu, Japan, triggering a powerful tsunami that travelled across the entire Pacific Ocean. This was regarded as the most powerful tsunami ever recorded by an instrument and assessing all its parameters will be beneficial for future research about this tsunami and other trans-oceanic tsunamis. A set of 30 DART Stations from all over the Pacific Ocean were used to produce a tsunami propagation map containing the arrival time of the travelled tsunami wave front and produce tsunami parameter decay over the distance travelled by the tsunami. It was shown that the tsunami wave front travelled the Pacific Ocean from Japan to Chile for about 20 hours since the earthquake. The similar arrival times between DART 21413-21419, DART 21414-52402, and DART 52406-46409 showing the possibility of a symmetry from the tsunami propagation. From the distance point of view, tsunami amplitude and energy evolution were shown to be decayed over the distance travelled from the source, where both of them showing a negative power relationship of -0.89 (R2=0.85) for the amplitude, -0.93 (R2=0.87) for the normalized amplitude (in the contest of uniform depth of 4500 m), and -1.76 (R2=0.98) for the normalized energy flux, respectively. An inverse estimation to assess the source area of the tsunami were done using the coefficient from the amplitude decay (-0.89) and resulting in the source amplitude value of 8.66 m with fault dimension of 100 x 50 km and slip displacement of 29.9 m. This was the highest tsunami measured till date in the Pacific Ocean using NOAA deep sensors. Further, the identification of tsunami wave front from the altimetry satellite was done and able to detect four Sea Level Anomaly (SLA) spikes above 0.3 m from three altimeter satellites, Jason 1, Jason 2, and Envisat. These results inferred that the tsunami propagation pattern in the Pacific Ocean is almost following the symmetrical uniform depth propagation. The attenuation of measured deep-water amplitude and energy flux per unit wave front from the deep sensors are also distance dependent with linear negative power relationship, unlike the period, velocity, and the wavelength of the tsunami.