Bulletin of the Seismological Society of America; February 2006; v. 96; no. 1;
p. 237-257; DOI: 10.1785/0120050052
© Seismological Society of America
Click on image to view larger version.
Figure 11. As Figure 9. (a) For a 5-day
period in January 2003, with a particularly intense wind storm (no rainfall).
The natural frequencies of the Library dramatically shorten for the duration of
the most intense windstorm, most notably in the east–west direction, but
also significantly for the north–south and torsional modes. The smaller
windstorm in the evening of January 6 appears slightly shifted in time from the
response; this may be due to variations in the winds between the Library and the
weather station at JPL. The mean frequencies are for the whole month of January.
(b) For a 22- day period, late August to early September 2002. Typical daily
variation during the summer months. Note correlation of rise in all three
natural frequencies during hottest days. 26 August, vibration testing; 3
September, M 4.8 Yorba Linda Earthquake.
