SEISMIC HAZARD AND RISK ASSESSMENT AND COMMUNICATION IN THE CENTRAL AND EASTERN UNITED STATES

WANG, Z., Kentucky Geological Survey, University of Kentucky, Lexington, Kentucky 40506, zmwang@uky.edu.

Seismic hazard describes a relationship between earthquakes of certain magnitude (or ground motions generated by the earthquakes) and their occurrence frequency. This relationship can be determined from seismic hazard analysis, such as probabilistic seismic hazard analysis (PSHA). The purpose of seismic hazard analysis is to provide parameters for estimating risk. Risk has different meanings among different professions, however. In general, risk can be quantified by three terms: probability, hazard (loss or other measurements), and time exposure. For example, in health sciences, risk may be defined as the probability of getting cancer if an average daily dose of a hazardous substance (hazard) is taken over a lifetime (70 years on average). In the financial market, risk may be defined as the probability of losing a certain amount of money over a period.

In seismology, risk may be defined as the probability of earthquakes with a certain magnitude or greater striking at least once in a region during a specific period. In earthquake engineering, risk was originally defined as the probability that ground motion at a site of interest exceeds a specific level (hazard) at least once in a period. Different seismic hazard analyses may provide different relationships between earthquakes of certain magnitude (or ground motions generated by the earthquakes) and their occurrence frequency. Therefore, a clear definition of seismic hazard and risk is necessary in any discussion and communication of the hazard and risk.