Seismic hazard and risk assessment in the intraplate environment: The New Madrid seismic zone of the central United States

Abstract

Although the causes of large intraplate earthquakes are still not fully understood, they pose certain hazard and risk to societies. Estimating hazard and risk in these regions is diffi cult because of lack of earthquake records. The New Madrid seismic zone is one such region where large and rare intraplate earthquakes (M = 7.0 or greater) pose signifi cant hazard and risk. Many different defi nitions of hazard and risk have been used, and the resulting estimates differ dramatically. In this paper, seismic hazard is defi ned as the natural phenomenon generated by earthquakes, such as ground motion, and is quantifi ed by two parameters: a level of hazard and its occurrence frequency or mean recurrence interval; seismic risk is defi ned as the probability of occurrence of a specifi c level of seismic hazard over a certain time and is quantifi ed by three parameters: probability, a level of hazard, and exposure time. Probabilistic seismic hazard analysis (PSHA), a commonly used method for estimating seismic hazard and risk, derives a relationship between a ground motion parameter and its return period (hazard curve). The return period is not an independent temporal parameter but a mathematical extrapolation of the recurrence interval of earthquakes and the uncertainty of ground motion. Therefore, it is diffi cult to understand and use PSHA. A new method is proposed and applied here for estimating seismic hazard in the New Madrid seismic zone. This method provides hazard estimates that are consistent with the state of our knowledge and can be easily applied to other intraplate regions.