To simulate tsunami propagations in real-time is a great challenge. All the previous attempts have focused either on running a model on the fly or on limited-source Green's functions (named after George Green). Even with a supercomputer and massively parallel computations, it would be very difficult to run a model on the fly in a vast transoceanic domain and yet still win the race for time against a fast moving tsunami (~700km/hour). The limited source Green's function approach can provide results very quickly, but unfortunately only for cases in which a tsunami originates within a few pre-assumed source regions.
The real-time simulation system illustrated here is based on a new method, referred to as the all-source Green's function (ASGF) method ( Xu 2007, Xu 2011 ). The method pre-calculates the fundamental response functions of a point of interest against all the sources distributed in the entire domain (hence the name all-source Green's function). When a tsunami trigging event (an earth quake, a submarine slide, or even an asteroid impact) occurs, the pre-calculated all-source Green's functions corresponding to the source region of the event will be loaded into RAM and multiplication with the source functions almost instantaneously gives the real response at the point of interest. The pre-calculated all-source Greens functions are dynamically consistent with the model, and the results are the same as if you ran the model on the fly but requires much less CPU time. As you will see in the next pages, the response to forcing anywhere in North Atlantic Ocean or in the India-Pacific Oceans can be determined within a few seconds using commonly available computer resources.
Xu 2007. The all-source Green's function and its applications to tsunami problems. Science of Tsunami Hazards, Vol. 26, No. 1, pages 59-69 (2007).
Xu 2011. The All-Source Green's Function of Linear Shallow Water Dynamic System: Its Numerical Constructions and Applications to Tsunami Problems, The Tsunami Threat - Research and Technology, Nils-Axel Mörner (Ed.), ISBN: 978-953-307-552-5, InTech.