Measurements of peak ground velocity v and acceleration a for earthquakes and mine tremors, with local magnitudes ranging from -0.8 to 6.4, have been analyzed in terms of a model of inhomogeneous faulting. The fault model involves the failure of a circular 'asperity' of radius ri surrounded by a previously faulted annular region of outer radius r0. The failure of the asperity results in seismic radiation with a characteristic frequency proportional to 1/r0 followed by lower-frequency radiation, proportional to 1/r1, as static equilibrium is regained over the larger region. For r0/ri≫1 both v and a are associated primarily with the failure of the asperity but also depend on the large-scale source parameters. Specifically, v = (βΔ&tgr;r0/μR)(0.10r0/ri+ 0.15), and a = (Δ&tgr;/&rgr;R)<0.30(r0/ri)2+0.45>, where β is the shear wave velocity, Δ&tgr; is the overall stress drop, μ is the modulus of rigidity, and &rgr; is density. The terms involving r0/ri correspond to the high-frequency radiation associated with the failure of the asperity, and the other terms indicate the peak parameters due to the broad-scale readjustment. Observations of peak ground motion for events with seismic moments ranging from 5¿1016 dyn cm indicate that r0/ri is normally in the range of 1--10 and appears to be independent of earthquake size. The inhomogeneous fault model also yields convenient expressions for the small-scale displacement and stress drop of the asperity failure as well as for the level of regional stress available to cause slip.