International Association of Seismology
and Physics of the Earth's Interior


Commission on Earthquake Generation

Process - Physics, Modelling, and Monitoring

for Forecast


Scope

The purpose of the Commission will consist in promoting advances of experimental and theoretical researches in the field of earthquake physics, with special emphasis to their forecast methods, development of new and existing models of seismic process at different scales and their validation in the natural frameworks of seismogenic regions and mines.

Earthquakes represent a class of non-linear processes, where the non-linearity of the system is related to the variety of processes, covering a wide range of spatial and temporal scales, which take part in the stress redistribution in the earth crust and generates power-law distributions that are often associated with the basic concepts of complexity. In the late ХХ-th century, several efforts have been devoted to the application of non-linear dynamics approaches to the description of earthquakes preparation and nucleation processes, as well as to the evaluation of the impact of such concepts on the problem of earthquake prediction. In this framework, studies assessing the relevance of space-time scales in the modeling and predictability of non-linear systems are envisaged.

The perception, according to which the preparation of a strong earthquake can be considered from common positions of the theory describing behavior of physical system in a vicinity of critical point, actively developed during last decades. Accordingly, when a strong earthquake approaches, specific features in the behavior of Earth's crust elements cease to be essential and, in the area of preparation of the earthquake, collective processes should be observed over a wide range of system scales. On the other hand, a system that is close to the critical state should be highly sensitive to even small external perturbations. Several works suggest that weak quasi-periodic perturbations can control/synchronize irregular relaxation process, such as seismicity driven by tectonic forces; these observations, however, are mainly qualitative or remain still unproved. Hence studies on triggering and synchronization of seismic/acoustic events by weak external forcing appear relevant to the modeling and prediction of earthquakes.

Recent advances in the representation of the fractal structure of geological environment, as well as the understanding of self-similarity of processes that characterize it at different scales and the self-organization of seismicity, suggest to apply in seismology methods from physics of non-equilibrium processes. This approach to the study of seismogenic processes provides the opportunity to make use of results from laboratory experiments, thus allowing for repeated experiments at known and controllable parameters, which are necessary for verification and comprehension of the basic laws and their dependence on tested parameters. In the meanwhile laboratory experiments are never fully representative, due to the different space and time scales involved and to the impossibility of accounting for all variety of processes involved in earthquake preparation. Therefore it is mandatory to check the properties derived from laboratory experiments against field observations.

Following a basically different approach, physical models for the entire cycle of earthquake generation, constrained by seismological and geodetic observations, can be developed. The newly available high quality positioning data (e.g. GPS and InSAR) may permit monitoring deformations, that can be combined with routinely updated seismic information. Realistic simulation models may thus provide a new framework for studying earthquake precursory phenomena and, once validated against available observations, may have direct application to earthquake hazard quantification.

Seismological observations at the mining enterprises are actual direction of researches of earthquake sources from the theoretical and practical point of view. Mines can be viewed as natural laboratories, where it is possible to investigate seismic processes at an intermediate scale level, between regional scale observations, on the one hand, and experiments on rock samples, on the other.

The Commission aims to promote research and discussion ranging from generalised scale invariance to the interpretation of earthquake as a critical point, from theoretical source models to rheological models of damage of rocks. Special attention must be paid to verification and validation of new and existing models, based on past observations and monitoring.