Earthquake probability in engineering—Part 2: Earthquake recurrence and limitations of Gutenberg-Richter b-values for the engineering of critical structures: The third Richard H. Jahns distinguished lecture in engineering geology

Abstract

Ellis L. Krinitzsky, 1993. Earthquake probability in engineering—Part 2: Earthquake recurrence and limitations of Gutenberg-Richter b-values for the engineering of critical structures Eng. Geol., 36: 000-000. Gutenberg-Richter b-values are dysfunctional for site-specific applications in the engineering of critical structures. Their dysfunction results from differences in the mechanism of faulting and nonuniformity in the occurrences of earthquakes over time and space. The mechanisms of faulting include stick slip, various categories of controlled slip, and a multitude of thermodynamic slip processes which range from rock melting to stress releases by hydrothermal and other fluids at or near lithostatic pressures. These processes cause accelerated fault movements and chaotic earthquake occurrences, while asperities and barriers along faults contribute to temporary clustering effects that develop characteristic earthquakes but do not give them continuity through time. B-line projections must incorporate these complexities, but they can do so only when they are inclusive for large, seismically active areas such as southern California, the Aleutian arc, etc. Within the relatively small earthquake source areas that determine damaging earthquake ground motions at individual engineering sites, b-values become dysfunctional at M ≥ 5.0. Because b-values are the determinants of probabilistic seismic hazard analyses, there are severe restraints on the usefulness of probabilistic methods to assign earthquake ground motions for the engineering of critical structures. The latter include major dams, nuclear power plants, liquefied petroleum gas installations, repositories for dangerous wastes, military command centers, sensitive industrial and defense installations, fire stations, schools, and hospitals.