Hello,
Thank you for your interest in the TELEMAC system.
The test case Okada was setup to ressemble the goutedo test case: creating a free-surface "blob" that we let go to fall on itself. Its sole purpose is to check the computation of the okada tsunami model. The fact that we compute the propagation of the wave as it goes out of the box without boundary reflection is just a nice thing to see, juste like the goutedo test case.
I believe the characteristics of the tsunami source term itself might have come from published literature of the 1755 Lisbon Tsunami - but no not sure anymore, it has been a while.
Hope this helps,
Sébastien.