University:
Boston University
Course:
CAS EE 645 | Physical Models in Remote Sensing
Academic year:

2023
Views:

160

Pages:

10
Author:

debatehl4dcq

Summary Characteristics of earthquake-generated tsunamis • Ocean basin and continental shelf: Small amplitude waves (wave amplitude is much smaller than wavelength/water depth); Long waves (wavelength is much larger than water depth); Dissipation (wave breaking and bottom friction) insignificant. • Coastal region: Strongly nonlinear transient flows; significant wave breaking induced and bottom boundary layer turbulence; sediment (debris) laden flows; 3D flows strongly affected by bathymetry, topography, and surface conditions. Part 6 Modeling earthquake-generated oceanic tsunamis  Phenomenal o Generation and evolution of tsunami waves in the neighborhood of the source region o Wave propagation in the deep ocean and into the shallow waters o Terminal (Coastal) effects: wave runup/drawdown and inundation  Methodology o Analytical solutions o Numerical simulations o Laboratory experiments Purposes of tsunami modeling • Forecasting and Warning – – – – Accurate wave heights Accurate arrival times Accurate inundation Accurate currents • Hazard Mitigation/Coastal Zone Planning – Accurate inundation areas and water levels – Impact potential (forces, erosion, interaction with structures and structural response, etc.) How to model tsunami generation? • Earthquake causes seafloor motions • Seafloor displacement generate surface gravity waves (tsunamis) Difficulties: • • Earth is a complex and heterogeneous media Different time scales for seismic waves and tsunamis (Rayleigh wave speed 4km/s; tsunami wave speed 0.2 km/s) Simplified Models: Linear elastic dislocation model (Okada, Bull. Seism. Soc. Am.1985) Example of earthquake-generated tsunamis Not all seafloor earthquakes cause tsunamis Comparison of 1964 Alaska & 2004 Sumatra Structures SUMATRA Okada’s dislocation theory provides the final seafloor displacement. 2011 Tohoku E/T Dip angle = 10 degree; Strike angle = 200 degree; Slip angle = 90 degree; The slip varies 30m to 50m; W = 200~300 km; L = 500 ~ 800 km.