Progress in Rotational Seismology

Based on the extensive investigation of rotational motion with its theory, seismometers, practical observations and their engineering applications, the researches and developments on rotational motion are summarized. The definition of the rotational component and the method of calculating the rotational component indirectly through the translational component are introduced in detail. On the basis of introducing some real observations of the rotational motions, in this paper it focuses on the classification of rotational seismograph with its respective principle, advantages and disadvantages. Also, the examples of rotational-component observation are presented. Moreover, the applications of rotational components in natural earthquake and exploration seismology are discussed. Our investigation demonstrates that the research of rotational motion is still in the experimental and initial stage, especially in China, and that the difference of seismic wave fields under different sources and different media should be the hotspots of the field research. And the development trend is to manufacture equipment with high precision and sensitivity with wider frequency band. The superiorities of the six-component observations need to be elaborated to reverse the fine structure of underground medium and earthquake sources in seismology and engineering through jointly utilizing of the rotational and translational components.