Unified approach to catastrophic events: from the normal state to geological or biological shock in terms of spectral fractal and nonlinear analysis - Eftaxias, K. A.; Kapiris, P. G.; Balasis, G. T.; Peratzakis, A.; Karamanos, K.; Kopanas, J.; Antonopoulos, G.; Nomicos, K. D. (Nat. Hazards Earth Syst. Sci., 2006)