By a process of matched filtering it is possible to deconvolve a small number of acceleration or strain records for the moment rate tensor of a seismic source. Theoretically, one horizontal accelerometer (or strain meter) or two vertical accelerometers is sufficient. Practically, five to ten records can be shown to suffice. Specifically, the mechanism of the Colombian event of July 31, 1970 can be retrieved from a sparse network of ten WWSSN vertical instruments.