source: anuga_work/production/hobart_2006/report/computational_setup.tex @ 3855

To set up a model for the tsunami scenario, a study area is first 
determined. Preliminary investigations have indicated that the
output from MOST should be input to ANUGA 
at the 100m water depth\footnote{ 
Preliminary investigations indicate that MOST and ANUGA compare
well at a water depth of 100 m. In addition, the resolution for
the MOST modelling indicate that it can theoretically model a
tsunami wave with a wavelength of 20-30 km. The wavelength of
the tsunami wave at the boundary in this scenario is approximately 20 km.}. 
Historical run-up heights have not been recorded in Tasmania, however
we would expect that a tsunami wave
would penetrate no higher than 20m in elevation for this scenario. As a result
we have bounded our study region at around the xm elevation.
Current computation requirements define a coastline
extent of around 100 km. Therefore, the study area of around 9300 km$^2$ 
covers approximately 100 km of
coastline and extends offshore to the 100m contour line and inshore to 
approximately 50m elevation. 

The finite volume technique relies on the construction of a triangular mesh which covers the study region. 
This mesh can be altered to suit the needs of the scenario in question. The mesh can be refined in areas of 
interest, particularly in the coastal region where complex behaviour is likely to occur. 
In setting up the model, the user defines the area of the triangular cells in each region of interest\footnote{Note that the cell 
area will be the maximum cell area within the defined region and that each 
cell in the region does not necessarily have the same area.}.
The cell areas should not be too small as this will cause unrealisticly long computational time, 
and not too great as this may inadequately capture important behaviour. 
%There are no gains in choosing the area to be less than the supporting data.
Figure \ref{fig:onslow_area} shows the study area with regions of difference cell areas. The total number
of cells is ?. 
Lateral accuracy refers to the distance at which we are confident in stating a region is inundated. 
Figure \ref{fig:hobart_area} shows the maximum triangular cell area and lateral accuracy for each region. 


\begin{figure}[hbt]

  %\centerline{ \includegraphics[scale=0.15]{../report_figures/hobart_resolution_zones.jpg}}

  \caption{Study area for the Hobart scenario highlighting four regions of increased refinement.
Region 1: Surrounds the coastal region with a cell area of 2500 m$^2$ (lateral accuracy 70 m).
}
  \label{fig:hobart_area}
\end{figure}


The final item to be addressed to complete the model setup is the 
definition of the boundary condition. As 
discussed in Section \ref{sec:methodology}, a Mw 8.5 and Mw 8.7 event provides
the tsunami source. The resultant tsunami wave is made up of a series
of waves with different amplitudes which is affected by the energy
and style of the event as well as the bathymetry whilst it travels
from its source towards South East Tasmania. 
The amplitude and velocity of each of these
waves are then provided to ANUGA as boundary conditions and propagated
inshore.