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Earth, Planets and Space
Fig. 4 | Earth, Planets and Space

Fig. 4

From: Noise classification for the unified earthquake catalog using ensemble learning: the enhanced image of seismic activity along the Japan Trench by the S-net seafloor network

Fig. 4

Visualization example of a decision tree. In this example, the first bifurcation point is \({N}_{p}^{4}\ge 2.5\) or not. \({N}_{p}^{4}<2.5\); then, go to the left branch, and the second bifurcation point is \({N}_{ps}^{17}\ge 4.5\) or not. This process repeated until the maximum branching depth yields the classification results of the pie chart. The color of each section in the pie chart indicates the labels of earthquakes and noise events given as a teacher. In the leftmost example, 2319 events meet this bifurcation condition, and although some earthquakes are included, we estimated the events as noise. This is an example of a single weak learner (decision tree); in ensemble learning, many such weak learners are combined to estimate the final label

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