This report describes the development of scaling relations between seismic moment and rupture area of earthquakes in stable continental regions (SCR). The report reviews existing relations, develops new relations, and compares the new relations with the existing relations. It also compares the scaling relations of SCR earthquakes with those in tectonically active continental regions (TCR). Three different methods of estimating rupture area—based on aftershocks, slip models, and duration—were used to analyze the relation between seismic moment and rupture area, using earthquake source parameters compiled from published literature. For each category of data, the relations obtained were not significantly different from those obtained by constraining them to be self-similar. Accordingly, these self-similar relations were adopted in this study. The stress drops corresponding to these scaling relations range from 51 to 86 bars, with an average of 65 bars. This value is comparable to the value of 58 bars obtained by Leonard [2010]. Because Leonard [2010] did not document his data and used an undifferentiated mixture of different ways of measuring fault area, the relation that he developed is less soundly based than that developed in this study. However, the two relations are not significantly different, and the Leonard [2010] relations have the advantage of having been derived in a self-consistent manner for a wide range of earthquake categories, including crustal earthquakes in tectonically active regions. Consequently, it is recommended that the Leonard [2010] scaling relations for SCR earthquakes be used for the NGA-East Project. To a first approximation, the results of this study and that of Somerville et al. [1997] indicate that the rupture areas of SCR earthquakes are about half those of TCR earthquakes, and their stress drops are about 2.8 times higher. Allmann and Shearer [2009] find less of a difference, presumably because their intraplate category includes some earthquakes that the NGA-East Project would assign to TCR instead of SCR. Their study indicates that the rupture areas of intraplate earthquakes are about two-thirds those of TCR earthquakes, and their stress drops are about two times higher.
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