THE ENGINEERING AND SCIENCE OF EARTHQUAKE RISK
PAUL CHRISTIAN JENNINGS
Because of the increasing population and urbanization of earthquake-prone areas, and because much new construction has inadequate earthquake resistance, the risk to society from earthquakes is growing, not decreasing. The degree of risk is also increased by the growing complexity and interdependence of the infrastructure of modern cities. Addressing the risk of disastrous earthquakes requires a coordinated focus of scientific, engineering and social efforts. Although in the public eye the primary scientific contribution is perhaps earthquake prediction, the major scientific contributions to coping with earthquake hazard are, in fact, in other areas. Many respected seismologists see earthquake prediction as a far distant goal, at best. Certainly, reliance upon earthquake prediction to reduce earthquake risk is not a practical strategy given the present state of knowledge. Much more important to the reduction of earthquake risk are the scientific studies delineating active faults and estimating the frequency of large earthquakes that these faults can generate. For example, studies using trenching and dendrochronology have allowed the dating of great prehistoric earthquakes along CaliforniaÕs San Andreas fault and in the Pacific Northwest, thereby permitting quantitative estimates of the likelihood of future shocks.
The engineering efforts to reduce earthquake risk range from such practical tasks as the improvement of building codes and standards of construction, to basic research on the character of near field ground motions and structural response. The adoption and enforcement of a good building code is the most broadly effective way to decrease earthquake risk, but there are many special structures and engineering systems which cannot be covered by a simple building code and that require special study and treatment. Included in this category are tall buildings; major bridges; base-isolated structures; port and harbor facilities; gas, water, electricity and sewage distribution and collection systems; communication and transportation systems; dams; offshore drilling towers; and hazardous facilities such as nuclear power plants and chemical storage tanks. Much of current earthquake engineering research focuses on ways to improve the earthquake performance of such important special structures and facilities.
In addition to the scientific and engineering features of earthquake risk reduction, there are important social and economic issues that are of primary concern to planners and social scientists. The principal issues in these areas include the problems of earthquake preparedness, response and recovery, as well as the challenges of effective land-use planning, earthquake insurance and restoration of economic vitality. For example, enormous investments in specialized manufacturing facilities, such as those in Silicon Valley, create a need for special attention to prevent excessive economic loss.