Figure 12. East–west components of USGS-Caltech Array in Millikan Library, M 5.4 Big Bear earthquake: velocity time series and FFT. Includes floors 1–9 and roof of Millikan Library as well as GSA. ("free-field" site) and MIK (on ninth floor of Millikan Library), plotted underneath the first and ninth channels. FFT plots are centered around the fundamental frequency (1.06 Hz) and first overtone (4.55 Hz) for the east–west direction. Also included are the two east–west mode shapes as identified from forced vibrations (Bradford et al., 2004).