Lithospheric stress and deformation

The study of the mechanisms, magnitudes, and modes of lithospheric stress and deformation occupies a central position in the discipline of Tectonophysics. It is therefore difficult in assembling a comprehensive review to place limits on what should be included. For example, one cannot discuss stress and deformation apart from considerations of the rheological models of the lithosphere which link the two and ultimately control the behavior of plates at their margins and in their interiors. Once admitting to the importance of rheological considerations in discussing stress and deformation, one is then compelled to include information relating to the thermal state of the lithosphere, since temperature is one of the foremost environmental variables controlling rheology. Furthermore, lithospheric processes cannot be considered in isolation from those affecting the asthenosphere, since surely there exists some coupling between the motion of the lithosphere and convection in the Earth's interior. In fact, an understanding of lithospheric stress and deformation can be considered a prerequisite to solving problems in geodynamics because it is through the lithospheric filter that one detects the consequences of thermal and compositional anomalies at greater depth. The topic of this report cannot even be cleanly separated from reviews in other disciplines such as Seismology and Geodesy. The magnitude and orientation of lithospheric stress is often indicated by earthquakes, while lithospheric strain can be observed geodetically. The philosophy I have adopted here is that some overlap with other review papers in this series is unavoidable, and probably desirable from the standpoint of emphasizing how recent work n other areas of geophysics has contributed to the advancement in our understanding of the lithosphere's state‐of‐stress and mechanisms of deformation. I have, however, resisted the temptation to include extraterrestrial studies, presumably covered in the Planetary section, despite the similar causes for deviatoric stress and deformational mechanisms operating on other terrestrial planets. Certainly ideas of how silicate materials behave and how lithosphere responds to internal forces benefit from the perspective of omparative planetology. Finally, in defining the scope of this portion of the U.S. National Report to the IUGG, I did not consciously exclude papers by non‐U.S. citizens, work done at non‐U.S. institutions, projects not funded by the U.S. Government, or however else “foreign” might be defined. Topics in geophysical research cannot be divided along political boundaries. However, I did not attempt to seek out articles written in languages other than English or published in journals not readily available in the United States, and I apologise for this obvious shortcoming.