The installation of very broadband seismic stations makes it possible to recover the source parameters of small earthquakes (2.5L<5.0) which occur at local and regional distances. If the gross crustal structure along the travel path is known, it is possible to use the P, SV and SH displacement waveforms from a single station of determine the seismic moment tensor. Although the details of the crustal structure strongly affect the body waveforms at regional distances, the signature of the seismic source orientation on the waveform is robust at frequencies less than 1--3 Hz. We explore the trade-offs between crustal model, hypocentral depth and filtering for a linear moment tensor inversion procedure. The procedure is tested on two small earthquakes which occurred in the Rio Grande Rift and were recorded at the IRIS/USGS station ANMO. The agreement between the single station moment tensor inversion fault plane parameters and those determined from local first motions is excellent. ¿ American Geophysical Union 1991