Automatic Tsunami Hazard Assessment System: “Tsunami Observer”

Abstract

The current prototype of a fully automatic earthquake tsunami hazard assessment system, “Tsunami Observer”, is described. The transition of the system to the active phase of operation occurs when information about a strong earthquake (Mw ≥ 6.0) is received. In the first stage, the vector field of coseismic displacements of the Earth’s crust is calculated by using the Okada formulas. In the calculations, use is made of data on the coordinates, the seismic moment, the focal mechanism, and the depth of the earthquake, as well as empirical patterns. In the second stage, the initial elevation of the water surface at the tsunami’s focus is determined with the vector field of coseismic displacements of the bottom and the distribution of ocean depths, and the earthquake’s potential energy is calculated. In the third stage, the intensity of the tsunami is estimated on the Soloviev–Imamura scale in accordance with the magnitude of the potential energy by using the empirical relationship that is obtained as a result of a statistical analysis of historical tsunami events. In the final stage, if the energy exceeds the critical value of 109 J, a numerical simulation of the tsunami is performed, which allows the determination of the predominant directions of wave energy propagation and estimation of the runup height on the nearest coast. In this work, data on the operation of the system over the last 3 years are presented.

Keywords

• submarine earthquake
• tsunami
• coseismic displacement
• long gravity waves
• numerical modeling
• early tsunami warning