Inverse problem 1 is often viewed as a formulation of structural parameter identification
(Trivailo et al., 2004) or structural model updating (Mottershead and Friswell, 1993; Friswell
and Mottershead, 1995; Ahmadian et al., 1998; Avitabile, 2000). Inverse problem 2 is a
formulation for load parameter identification or load updating (Chock and Kapania, 2003;
Chock and Kapania, 2004).