Peak values and time series data are available for the 20040930 18:54 UTC,
Mw 5.0, Parkfield, California aftershock (lat 35.984, lon -120.550):
http://nsmp.wr.usgs.gov/data_sets/20040930_1854.html

Regards,

Kent Fogleman
____________________________________________________
Kent A. Fogleman
U.S. Geological Survey
National Strong-Motion Data Center
345 Middlefield Rd., MS 977
Menlo Park, CA 94025

office: 650-329-4745
e-mail: fogleman@usgs.gov
web:    http://nsmp.wr.usgs.gov