The following information obtained from UNAVCO's online DOI system:
(https://www.unavco.org/data/doi/search/search.html)

SAF Creeping Segment GPS Network - GR8V-Martin Ranch-Great Valley P.S.
Start: 21-Jan-2003
End: 27-Apr-2008
DeMets, Charles, 2004, SAF Creeping Segment GPS Network - GR8V-Martin Ranch-Great Valley P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T5862DKQ