ture initiation point. This motivates a need for data on the center of energy radiation (ground-motion centroid), the conventional hypocenter, and the spatial distribution of ground motion. With these requirements, detection and location algorithms for real-time warning will differ from standard procedures at traditional seismographic stations.
For the past 25 years, the NEHRP has sponsored a combination of basic and applied research on the causes of earthquakes, their distribution, and their damage to the built environment (Appendix A). The review in this chapter demonstrates that this information is paying off in the ability to anticipate and reduce earthquake destruction. However, the degree to which the knowledge gained through research has been utilized in coordinated programs of risk mitigation has been the focus for criticism of the NEHRP strategy. In a 1995 report to the U.S. Congress, the Office of Technology Assessment stated (104):
NEHRP has made significant contributions toward improving our understanding of earthquakes and strategies to reduce their impact. However, much of the United States remains at risk for significant earthquake losses. Risk-reduction efforts lag far behind the knowledge base created by research; this lag or implementation gap, reflects the limitations of NEHRP’s information-based strategy for encouraging nonfederal action.
Considerable controversy surrounds which types of loss reduction measures should be implemented by government and the private sector through regulatory policies, economic incentives, long-term investments, and public education. Part of the debate concerns the role of scientific research in closing the implementation gap. The key question is: how can researchers participate more effectively in translating the technical understanding of earthquake phenomena into civic actions?
This chapter has explored the great utility of combining seismic hazard analysis with engineering-based performance estimates to produce measures of earthquake risk, in terms of either the damage expected during the lifetime of an individual structure or the annualized economic loss expected for a specified region. Three further steps are necessary to reduce potential losses:
Mitigation options must be identified and evaluated. These options include improved building codes, design enhancements, retrofitting, land-use planning, and insurance. Evaluation must include assessments of the cost and effectiveness of each option to reduce risk.