B. U. Uslu

Direct energy estimation of the 2011 Japan tsunami using deep-ocean pressure measurements

[1]xa0We have developed a method to compute the total energy transmitted by tsunami waves, to the case where the earthquake source is unknown, by using deep-ocean pressure measurements and numerical models (tsunami source functions). Based on the first wave recorded at the two closest tsunameters (Deep-Ocean Assessment and Reporting of Tsunamis (DART)), our analysis suggests that the March 11, 2011 Tohoku-Oki tsunami generated off Japan originated from a 300–400 km long and 100 km wide area, and the total propagated energy is 3xa0×xa01015J (with 6% uncertainty). Measurements from 30 tsunameters and 32 coastal tide stations show excellent agreement with the forecasts obtained in real time. Our study indicates that the propagated energy and the source location are the most important source characteristics for predicting tsunami impacts. Interactions of tsunami waves with seafloor topography delay and redirect the energy flux, posing hazards from delayed and amplified waves with long duration. Seafloor topography also gives its spectral imprint to tsunami waves. Travel time forecast errors are path-specific and correlated to the major wave scatterers in the Pacific. Numerical dissipation in the propagation modeling highlights the need of high-resolution inundation models for accurate coastal predictions. On the other hand, it also can be used to account for physical dissipation to achieve efficiency. Our results provide guidelines for the earliest reliable tsunami forecast, warnings of long duration tsunami waves signals and enhancement of the experimental tsunami forecast system. We apply the method to quantify the energy of 15 past tsunamis, independently from earthquake magnitudes. The small tsunami to seismic radiation energy ratios, and their variability (0.01–0.8%), reinforce the importance of using deep-ocean tsunami data, the direct measures of tsunamis, for estimates of tsunami energy and accurate forecasting.

Observed and Modeled Currents from the Tohoku-oki, Japan and other Recent Tsunamis in Northern California

AbstractnWe investigate the currents produced by recent tsunamis in Humboldt Bay and Crescent City, California. The region is susceptible to both near-field and far-field tsunamis and has a historic record of damaging events. Crescent City Harbor, located approximately 100xa0kms north of Humboldt Bay, suffered US

Development Of New Databases For Tsunami Hazard Analysis In California

28 million in damages from strong currents produced by the 2006 Kuril Islands tsunami and an additional US

Solomon Islands 2007 Tsunami Near-Field Modeling and Source Earthquake Deformation

26 million from the 2011 Japan tsunami. In order to better evaluate these currents in northern California, we deployed a Nortek Aquadopp 600xa0kHz 2D acoustic Doppler current profiler (ADCP) with a 1-min sampling interval in Humboldt Bay, near the existing National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) tide gauge station. The instrument recorded the tsunamis produced by the Mw 8.8 Chile earthquake on February 27, 2010 and the Mw 9.0 Japan earthquake on March 11, 2011. One other tsunami was recorded on the Humboldt Bay tide gauge during the period of ADCP operation, but was not visible on the ADCP, suggesting a threshold water level value of about 0.2xa0m to produce an observable ADCP record. The 2010 tsunami currents persisted in Humboldt Bay for approximately 30xa0h with peak amplitudes of about 0.35xa0m/s. The 2011 tsunami signal lasted for over 40xa0h with peak amplitude of 0.84xa0m/s. The strongest currents corresponded to the maximum change in water level approximately 67xa0min after the initial wave arrival. No damage was observed in Humboldt Bay for either event. In Crescent City, currents for the first three and one-half hours of the 2011 Japan tsunami were estimated using security camera video footage from the Harbor Master, approximately 70xa0m away from the NOAA–NOS tide gauge station. The largest amplitude tide gauge water-level oscillations and most of the damage occurred within this time window. The currents reached a velocity of approximately 4.5xa0m/s and six cycles exceeded 3xa0m/s during this period. Measured current velocities both in Humboldt Bay and in Crescent City were compared to calculated velocities from the Method of Splitting Tsunamis (MOST) numerical model. The frequency and pattern of current amplification and decay at both locations are replicated by the MOST model for the first several hours after the tsunami onset. MOST generally underestimates 2011 peak current velocities by about 10–30xa0%, with a few peaks by as much as 50xa0%. At Humboldt Bay, MOST predicted attenuation of the signal after 4xa0h but the actual signal persisted at a nearly constant level for at least twice as long. The results from this project demonstrate that ADCPs can effectively record tsunami currents for small to moderate events and can be used to calibrate and validate models (i.e., MOST) in order to better understand hazardous tsunami conditions within harbors.