Reply Comment on " Earthquake Source Spectra in Eastern North America

Haddon (1996) proposes a theoretical model for earthquake source spectra in eastern North America (ENA), based on certain assumptions regarding the rupture process. He shows that if ENA earthquakes are characterized by very high rupture velocities and fractional stress drop, then their high-frequency S-wave radiation is strongly enhanced relative to that predicted by the simple Brune (1970) source model. Haddon discusses previous analyses of ENA ground motions, which appear to be at odds with his model, concluding that these analyses contain misinterpretations of both data and theory. He disagrees specifically with the results obtained by Boatwright and Choy (1992), Boore and Atkinson (1992), Atkinson (1993), Boatwright (1994), and Atldnson and Boore (1995). His discussion of our results is mistaken in many points, as we describe in the following.