Tectonic Stress in the Lithosphere

Tectonic stress in the Earth's lithosphere not only reflects the forces acting on the lithospheric plates, some of which are responsible for plate motion, but also controls the locations and magnitudes of natural phenomena which have a substantial impact on humankind's activities and well-being. This book covers observational techniques, whereby stress can be directly measured or inferred, as well as a variety of theoretical approaches which help to explain or predict observations. Contributors were asked by the organizers of the Discussion Meeting (held in April 1991) to write articles which review their chosen field; thus it is intended that this volume will be of use to those with a general interest in lithospheric stress as well as to specialists in the subject.
Lithospheric stress is discussed at a variety of scales. At the largest scale the forces acting on whole plates and at their edges and the global balance of these forces. At least seven different forces have been identified which either drive the individual plates (slab pull, ridge push) or resist their motion (plate drag, etc.). The ridge-push force has a particularly important effect on intraplate tectonic stress, especially beneath oceanic areas. Special problems arise in explaining stress at transform plate boundaries and in some major mountain ranges. On the other hand observations at the Earth's surface, in boreholes or at greater depths (from earthquake focal mechanisms) detect the resultant of these numerous forces, and their interpretation and resolution into component parts is also discussed in several papers. In some cases it is possible to make observations from which deductions about past tectonic stress can be made.