Bulletin of the Seismological Society of America; February 2006; v. 96; no. 1;
p. 237-257; DOI: 10.1785/0120050052
© Seismological Society of America
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Figure 8. Deviation from the mean natural frequency for the three fundamental
frequencies at MIK, May 2001 through November 2003. Fundamental
frequencies for each hourly FFT are picked from the peaks in
Figure 6, then the deviation
from the average is determined. The hourly peak is shown in the thin green line
for each frequency; the thick black line tracks the daily average. The thick red
horizontal line is the average frequency. Daily rainfall (black), maximum wind
gust (green), and maximum temperature (red) from JPL are plotted at the bottom.
Vertical blue dashed-dot and red dashed lines indicate days with forced
vibration shaking of the library, and earthquakes with motions exceeding 2.5
cm/sec2 at station MIK, respectively, which produce large
deviations from the mean (Earthquakes: 9/9/01, M 4.2 Beverly Hills,
7 cm/sec2; 30/10/01, M 6.1 Anza, 2.8
cm/sec2; 3/9/02, M 4.8 Yorba Linda, 5 cm/sec2;
22/2/03, M 5.4 Big Bear, 18 cm/sec2) Note: forced vibration
with full weights generates 8 cm/sec2 at north–south
fundamental mode.
