Long-period and broadband body waves from 14 digital seismic stations are used to investigate the rupture process of the December 7, 1988 earthquake near Spitak, Armenia, USSR. The inversion of these data gives the following centroidal source parameters: strike 299¿, dip 64¿, rake 151¿, depth 6.3 km and seismic moment 1.5¿1019 Nm, indicating that on average the earthquake had a strike-slip mechanism with a substantial reverse component. The broadband waveforms, however, show significant complexity; they are best fit with a source model that includes three sub-events, very similar in size, but with distinct focal mechanisms and locations. Rupture apparently initiated as a shallow reverse fault at a point of maximum bending on a right-lateral strike-slip fault, and then extended bilaterally, first towards the southeast and then towards the west. This interpretation agrees with the aftershock distribution and fault lineations observed on LANDSAT images. ¿ American Geophysical Union 1989