Crust Macrofracturing as the Evidence of the Last Deglaciation
This work provides incremental insights into geological structures in Finland, linking seismic anomalies to deglaciation effects.
The study applied the k-nearest neighbors algorithm to seismic data from Finland, producing a Moho depth map and identifying a central low S-wave velocity area attributed to water-saturated cracks, concluding that macrofracturing resulted from the last deglaciation.
Machine learning methods were applied to reconsider the results of several passive seismic experiments in Finland. We created datasets from different stages of the receiver function technique and processed them with one of basic machine learning algorithms. All the results were obtained uniformly with the $k$-nearest neighbors algorithm. The first result is the Moho depth map of the region. Another result is the delineation of the near-surface low $S$-wave velocity layer. There are three such areas in the Northern, Southern, and central parts of the region. The low $S$-wave velocity in the Northern and Southern areas can be linked to the geological structure. However, we attribute the central low $S$-wave velocity area to a large number of water-saturated cracks in the upper 1-5 km. Analysis of the structure of this area leads us to the conclusion that macrofracturing was caused by the last deglaciation.