Statistical Estimation of Changes in the Dominant Frequencies of Structures in Long Noisy Series of Monitoring Data
Figure 9
(a) All significant frequency peaks in the area between 0 and 3 Hz identified during the 5 annual surveys. A break is induced in the vertical axis for presentation reasons. A dramatic shift in frequencies is evident between 2007 and 2013. (b) Significant frequency peaks for the years after 2009 and further on. For the years 2010–2013 only the frequency peaks below 1 Hz were chosen and used in the analysis resulting in a smaller set of points compared with the set of (a). There is some evidence of lowering in the dominant frequency, but its location is not well defined.
