Figure 1: Artificial data tests. Gray: artificial noisy data added to three perturbations each simulating one property of P and S waves. Dark (light) gray: vertical (horizontal) component of ground displacements. Ns.Z : noise only (vertical component of a 3-dimensional random motion) ; F.Z : frequency changes (vertical component); A.(ZEN): amplitude changes (three components) ; P.(ZEN): vertically polarized motion added at 10/3 s and horizontally polarized motion added at 5s (three components). Characteristic functions are represented by overlying colored lines.
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