HISTORY OF THE METHODS/FLOW CHART ABOUT THE AUTHOR/CV Multiple
Arrivals in Wave Propagation Level set methods and Fast Marching
Methods are designed to track a propagating interface, and find
the first arrival of the interface as it passes a point. One way
to think about this is to imagine that the front's boundary is a
propagating flame that separates two regions: a burnt part
behind the front and an unburnt part in front of the flame. Once
a piece of ground is burnt, is burnt, it stays burnt: this
corresponds to an entropy condition which insures that the
motion is irreversible, and that the first arrival time when the
disturbance hits is what is measured. However, there are many
situations, like propagating sound waves, in which later
arrivals are also important. In the drawings below, a wave
crosses over itself as it moves, creating both initial and later
arrivals: A good example of the important of these later
arrivals is in geophysical imaging, in which one tries to
predict what lies beneath the earth's