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
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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF
SEISMOTECTONIC TSUNAMIS
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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF
SEISMOTECTONIC TSUNAMIS
WinITDB, 2007
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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF
SEISMOTECTONIC TSUNAMIS
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INITIAL CONDITIONS or 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/
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INITIAL CONDITIONS or roundabout manoeuvre

• 3. Permanent vertical bottom deformations
• the Yoshimitsu Okada analytical formulae
• numerical models

4. Long wave theory
Central Kuril Islands, 15.11.2006
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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF
SEISMOTECTONIC TSUNAMIS
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OPTIMAL INITIAL CONDITIONS FOR SIMULATION OF
SEISMOTECTONIC TSUNAMIS
The roundabout manoeuvre means
Initial Elevation Vertical Bottom Deformation
???
There are a few reasons why
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Dynamic bottom deformation (Mw8)
Andrey Babeyko, PhD, GeoForschungsZentrum,
Potsdam
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Dynamic bottom deformation (Mw8)
permanent bottom deformation
duration 10-100 s
Andrey Babeyko, PhD, GeoForschungsZentrum,
Potsdam
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Period of bottom oscillations
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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
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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
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1. Elastic oscillations do not propagate upslope
2. Elastic oscillations and gravitational waves are
   not coupled (in linear case)

Linear Incompressible!
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Initial Elevation Vertical Bottom Deformation
???
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Smoothing ?minH
exponentially decreasing function
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Initial Elevation Vertical Bottom Deformation
Due to smoothing
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Permanent bottom deformations
vertical
horizontal
Central Kuril Islands, 15.11.2006
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Sloping bottom and 3-component bottom
deformation contribution to tsunami
Normal to bottom
Bottom deformation vector
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Sloping bottom and 3-component bottom
deformation contribution to tsunami
traditionally under consideration
traditionally neglected
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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.
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Simple way out for practice
Instant generation
If you cant have the best make the best of what
you have
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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
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Linear shallow water theory
Initial conditions
Boundary conditions
at shoreline
at external boundary
Initial elevation
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15.11.2006
Initial ElevationVertical Bottom Deformation
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15.11.2006
Smoothing Initial Elevation from Laplace Problem
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13.01.2007
Initial ElevationVertical Bottom Deformation
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13.01.2007
Smoothing Initial Elevation from Laplace Problem
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Comparison of runup heights calculated using
traditional (pure Z) and optimal (Laplace XYZ)
approach
15.11.2006
13.01.2007
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Conclusions

1. Optimal method for the specification of initial
   conditions in the tsunami problem is suggested
   and proved
2. The initial elevation is determined from 3D
   problem in the framework of linear potential
   theory
3. Both horizontal and vertical components of the
   bottom deformation and bathymetry in the vicinity
   of the source is taken into account
4. Short wave components which are not peculiar to
   gravitational waves generated by bottom motions
   are removed from tsunami spectrum.

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Thank you for your attention!
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15 Nov 2006
13 Jan 2007
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15 Nov 2006
13 Jan 2007