Assessment of seismic hazard near faults of uncertain type: Inter-plate versus intra-plate

Maximum magnitude is an important input parameter in seismic hazard analysis, but may be difficult to determine directly on the basis of available seismological data. Moreover, there is evidence that the scaling law relating maximum magnitude to fault length for inter-plate faults may differ from the law for intra-plate faults. Thus uncertainty as to the fault type can complicate the problem of determining maximum magnitude. We present a method for examining the implications for seismic hazard analysis of uncertainty regarding fault type. We apply the method to a simple constructed example and find that the problem of assessing fault type can be far more critical to the hazard assessment than the exact statement of fault geometry, especially for sites that are distant from the fault.