When thinking, at the beginning of the new century, on our horizons in seismology, we might return to the old question related to the seismic ro- tion effects and waves. Seismology, with its spectacular achievements instrumentation, data processing, seismic tomography and source process theories – remains practically confined to linear ideal elasticity (isotropic or anisotropic). Numerous renown seismologists have tried to go beyond this horizon. As concerns rotation waves, such attempts were inspired by numerous macroscopic observations pointing out the rotation effects, often observed on the ground surface. However, this problem has been app- ently closed by Mallet in 1862, who gave the following explanation: ro- tions of a body on the surface are due to a sequence of impacts of different seismic phases emerging under different angles. Later on, in 1937, I- mura underlined an influence of different inertia moments of an inflicted body. Thus, the surface rotation effects – rotation of some objects on the ground surface – were explained as being caused by the consecutive inc- nations and recovery of these objects to the vertical, when hit by the in- dent seismic body or surface waves. The final position of the object could become slightly twisted in comparison to its former place; the differences between the inertia tensor moments of the object and/or its attachment (as related to friction resistance of binding) to the ground surface play an - portant role.
This is the first book on rotational effects in earthquakes, a revolutionary concept in seismology. Existing models do no yet explain the significant rotational and twisting motions that occur during an earthquake and cause the failure of structures. This breakthrough monograph thoroughly investigates rotational waves, basing considerations on modern observations of strong rotational ground motions and detection of seismic rotational waves. To describe the propagation of such waves the authors consider structured elastic media that allow for rotational motions and rotational deformations of the ground, sometimes stronger than translational deformations. The rotation and twist effects are investigated and described and their consequences for designing tall buildings and other important structures are presented. The book will change the way the world views earthquakes and will interest scientists and researchers in the fields of Geophysics, Geology and Civil Engineering.
