| Summary: | Quantifying Changes in the seismic velocity (dv/v) from repeating sources or ambient noise surveys is an established tool in seismology. dv/v has been shown to correlate to a multitude of parameters such as stress variations, pore pressure changes, and modifications in the microscopic and macroscopic integrity of the sampled medium (i.e., “damage”). In turn, these parameters are impacted by an even greater number of mechanisms, for example, precipitation, temperature, surface loading, seismic activity, hydrology, volcanic activity, or tidal forces. However, their relationships to dv/v are often non-linear, hard to quantify, and poorly understood. Additionally, for “field data”, it can be challenging to decipher the contribution of each individual parameter to dv/v changes. In this work, we analyse continuous seismic data and interdisciplinary datasets from Mt St Helens (USA) and the Kamchatka peninsula (Russia) to illustrate the diversity of mechanisms impacting dv/v and discuss potential strategies to unravel the observations. We show that, for volcanic areas in particular, analysing dv/v is a complex task due to the addition of volcanic activity, high-relief topography, and strongly heterogeneous subsurface structures.
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