Statistical Estimation of Changes in the Dominant Frequencies of Structures in Long Noisy Series of Monitoring Data

Figure 10

Results from application of the SNHT on the frequency estimates from the surveys covering the years 2009 to 2013. A clear frequency shift is detected between 2009 and 2010. A horizontal, dashed line in the bottom diagram indicates the 95% statistical significance level for the test, while vertical lines indicate the limits of the data sets corresponding to different annual surveys. A gray-shaded area marks the distance between the point of the real shift and the point of the shift identified by the SNHT.