STOR Colloquium: Jonathan M. Lees, UNC-Chapel Hill
Jonathan M. Lees
University of North Carolina at Chapel Hill
Geophysical Time Series Analysis on Volcanoes:
Can we quantify non-linearity?
Most geophysical processes are aperiodic noisy, intermittent and transient. This requires specialized methods for time series analysis, that seek patterns in time series that vary in space and time. I present here examples from research on exploding volcanoes that exhibit tremor that appears to be resonant but likely results from nonlinear feedback systems. The physical models for these observations are highly controversial, so detailed analysis of patterns observed in the time series represents a significant challenge for understanding volcano dynamics. Seismic and Acoustic waves will be presented at a number of volcanoes, including Karymsky (Kamchatka, Russia), Santiaguito (Ecuador), Tungurahua (Ecuador) and others. Methods involving time-domain and frequency domain analysis, wavelet transforms, Hilbert-Huang empirical mode approaches and Bispectral decomposition will be illustrated.