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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS. M.A. Nosov , S.V. Kolesov Faculty of Physics M.V.Lomonosov Moscow State University, Russia. OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS.
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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS M.A. Nosov, S.V. Kolesov Faculty of Physics M.V.Lomonosov Moscow State University, Russia
OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS
OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS [WinITDB, 2007]:
OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS
INITIAL CONDITIONSor “roundabout manoeuvre” • 1. Earthquake focal mechanism: • Fault plane orientation and depth • Burgers vector 2. Slip distribution Central Kuril Islands, 15.11.2006 [http://earthquake.usgs.gov/]
INITIAL CONDITIONSor “roundabout manoeuvre” • 3. Permanent vertical bottom deformations: • the Yoshimitsu Okada analytical formulae • numerical models 4. Long wave theory Central Kuril Islands, 15.11.2006
OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS
OPTIMALINITIAL CONDITIONS FOR SIMULATION OF SEISMOTECTONIC TSUNAMIS The “roundabout manoeuvre” means Initial Elevation = Vertical Bottom Deformation ??? There are a few reasons why…
Dynamic bottom deformation (Mw=8) [Andrey Babeyko, PhD, GeoForschungsZentrum, Potsdam]
Dynamic bottom deformation (Mw=8) permanent bottom deformation duration~10-100 s [Andrey Babeyko, PhD, GeoForschungsZentrum, Potsdam]
Time-scales for tsunami generation L is the horizontal size of tsunami source; H is the ocean depth g is the acceleration due to gravity c is the sound velocity in water Tsunami generation is an instant process if finite duration However, if instant ocean behaves as a compressible medium
Time-scales for tsunami generation L is the horizontal size of tsunami source; H is the ocean depth g is the acceleration due to gravity c is the sound velocity in water traditional assumptions (i.e. instant & incompressible) are valid Tsunami generation is an instant process if finite duration instant However, if Compressible ocean ocean behaves as a compressible medium
Elastic oscillations do not propagate upslope • Elastic oscillations and gravitational waves are not coupled (in linear case) Linear = Incompressible!
“Smoothing”: min~H exponentially decreasing function
Initial Elevation = Vertical Bottom Deformation Due to “smoothing”
Permanent bottom deformations vertical horizontal Central Kuril Islands, 15.11.2006
Slopingbottom and 3-component bottom deformation: contribution to tsunami Normal to bottom Bottom deformation vector
Slopingbottom and 3-component bottom deformation: contribution to tsunami traditionallyneglected traditionallyunder consideration
Tsunami generation problem: Incompressible= Linear Linear potential theory (3D model) 1) Dynamic bottom deformation (DBD) Not instant! 2) Phase dispersion is taken into account Disadvantages: 1) Inapplicable under near-shore conditions due to nonlinearity, bottom friction etc.; 2) Numerical solution requires huge computational capability; 3) Problem with reliable DBD data.
Simple way out for practice Instant generation If you can’t have the best make the best of what you have
Simple way out for practice Instant generation Not only vertical but also horizontal bottom deformation is taken into account Permanent bottom deformations (all 3 components!) “Smoothing”, i.e. removing of shortwave components which are not peculiar to real tsunamis
Linear shallow water theory Initial conditions: Boundary conditions: at shoreline at external boundary Initial elevation
15.11.2006 Initial Elevation=Vertical Bottom Deformation
15.11.2006 Smoothing: Initial Elevation from Laplace Problem
13.01.2007 Initial Elevation=Vertical Bottom Deformation
13.01.2007 Smoothing: Initial Elevation from Laplace Problem
Comparison of runup heights calculated using traditional (pure Z) and optimal (Laplace XYZ) approach 15.11.2006 13.01.2007
Conclusions: Optimal method for the specification of initial conditions in the tsunami problem is suggested and proved; The initial elevation is determined from 3D problem in the framework of linear potential theory; Both horizontal and vertical components of the bottom deformation and bathymetry in the vicinity of the source is taken into account; Short wave components which are not peculiar to gravitational waves generated by bottom motions are removed from tsunami spectrum.
15 Nov 2006 13 Jan 2007
15 Nov 2006 13 Jan 2007