There are probably no other fields than the fields of civil engineering that extensively studies and deals with a variety of natural phenomena and geophysical structures. Researchers in the field have accumulated a vast amount of knowledge about geophysical processes and have learnt how to cope with them. But, when it comes to natural disasters such as typhoons, earthquakes and land slides, prediction of their occurrences is still a difficult task. One of the reasons for this is that the geophysical processes are nonlinear dynamical processes. Slight changes in initial conditions will in general produce large changes in results, and prediction of subsequent happening is very difficult. Thus, a vast amount of accumulation of experimental knowledge may help but will never be enough to exactly predict formidably adverse geophysical processes.
Here, researchers in civil engineering, mathematics and physics gathered together and formed a "Fractal Study Group" to look at problems from different point of views. We had met usually a few times a year to discuss new features, especially fractal phenomena as outcomes of nonlinear dynamical processes. Engineers and physicists have applied fractal analysis to the problems, quite often to those that have been labeled as "difficult" or "impossible" to solve by existing techniques. Mathematicians have played an important role in our group as a watch dog, so that applications of fractal analysis without reality have been warned.
Topics included in this special issue range from global climatic changes to damage evaluation of lifeline network systems. Throughout these vastly different subjects, a common theme is the fractal. Some of the topics are more physically well defined than others and the adaption of fractal approaches to those problems have been challenged. However, it is our wish to learn more about fractal itself and its limitation through its applications, and furthermore to use it ultimately for the prediction and prevention of natural disasters.
Finally, a list of the members participated in our study group is attached below.
Masami Nakagawa
(editor of this issue)