Promise and Paradox: Why Improved Knowledge of Plate Tectonics Has Not Yielded Correspondingly Better Earthquake Hazard Maps

The discovery of plate tectonics in the 1960s offered the promise of a physical foundation for earthquake hazard assessment. In subsequent years, knowledge of the geometry and rates of plate motions has improved dramatically, in part due to the advent of space-based geodesy and recognition that many plate boundaries are diffuse zones. In addition, space-based geodesy confirmed that many plate boundaries are diffuse zones, as suggested by the distribution of seismicity, topography, and active faulting. This chapter overviews why, despite advances in understanding plate motions, crustal deformation, and earthquakes, seismic-hazard assessments often do not do as well as we would like. It also suggests some ways to do better. Paradoxically, using the rapidly growing knowledge of plate boundaries and the motion on them in efforts to assess seismic hazards has yielded results that are less satisfactory than might be hoped. The chapter further reviews some of the recent work on the topic to explore why.