Selection of time-variant features for earthquake classification at the Nevado-del-Ruiz volcano

Seismic event recognition is an important task for hazard assessment, eruption prediction and risk mitigation, since it can be used to determine the state of a volcano. Usually, expert technicians read features extracted from the seismogram, such as, cepstral derived coefficients, energy centroids, instant frequency, instant envelop, among others. However, there are few studies about the selection of important features for classifying several types of seismic events, i.e., taking into account the temporal contribution of each considered feature. This paper presents a feature selection strategy based on a relevance measure of time-variant features for seismic event classification. In this research, features are selected as those with the maximal information preserved within the time analysis. Since features selection stage is performed by incremental training, a simple k-nearest neighbor classification rule is used to properly determine the dimension of the final feature set. The employed feature extraction and feature selection methodologies are tested on an isolated event recognition task. The database used to test the methodology is composed of the following classes: volcano-tectonic, long period earthquakes, tremors and hybrid events. Data was recorded at the seismic monitoring stations located at the Nevado-del-Ruiz volcano, Colombia. Using a classifier based on hidden Markov models, accomplished results exhibit a performance improvement from 78% to 88% using the proposed methodology in comparison to the state-of-the-art feature sets.