source: anuga_work/production/hobart_2006/report/interpretation.tex @ 7272

The main features of the
tsunami wave and resultant inundation ashore is described in this section. 
We have
chosen a number of locations to illustrate the features
of the tsunami as it approaches and impacts South East Tasmania.
These locations align with those in the paleotsunami report.
These locations
are described in Table \ref{table:locations} and shown in 
Figure \ref{fig:points}. The water's stage and speed 
at each of these locations are shown
as a function of time in the series of graphs shown in
Appendix \ref{sec:timeseries}. It is assumed that the earthquake is
generated at the beginning of the simulation, i.e. time = 0 minutes.
Stage is defined as the absolute
water level (in metres) relative to AHD. Both stage and speed 
(in metres/second) for
each scenario (Mw 8.7 and Mw 8.5) are shown
on consistent scales to allow comparison between point locations.
As a useful benchmark, Table \ref{table:speedexamples}
describes typical examples for a range of speeds found in the 
simulations. 

\begin{table}[h]
\label{table:speedexamples}
\caption{Examples of a range of velocities.}
\begin{center}
\begin{tabular}{|l|l|}\hline
{\bf Velocity (m/s)} & {\bf Example} \\ \hline
1 & leisurely stroll pace\\ \hline
1.5 & average walking pace \\ \hline
%2 & 100m Olympic male freestyle \\ \hline
%3 & mackeral \\ \hline
4 & average person can maintain running for 1000m \\ \hline
%5 & blue whale \\ \hline
10 & 100m Olympic male sprinter \\ \hline
16 & car travelling in urban zones (60 km/hr) \\ \hline
\end{tabular}
\end{center}
\end{table}

A tsunami wave typically has a small amplitude and typically travels at 100's of kilometres per hour. 
The low amplitude complicates the ability to detect
the wave. As the water depth decreases, 
the speed of the wave 
decreases and the amplitude grows. Another important feature of tsunamis 
is drawdown. This means that the water is seen to retreat from the beaches
before a tsunami wave 
impacts that location. Other features 
include reflections (where the wave is redirected due to the 
influence 
of the coast) and shoaling (where the wave's amplitude is amplified
close to the coast due to wave interactions).
These features are seen in these scenarios; there is a small wave, followed
by a large drawdown and then a large secondary wave. 

The bathymetry and geography of the region has played a role in 
directing or attentuating the tsunami wave. The tsunami wave is 
travelling from the south west of the area. The wave is seen to attentuate as it 
travels towards the Derwent River.