Systematic analysis of long-period earthquakes : Gorely volcano, Kamchatka

Gorely, being one of many active volcanoes in Kamchatka, stands out due to the rich magmatic history reflected in its composite structure and persistent degassing activity. In 2013–2014, a temporary network of 20 seismic stations was installed on the volcano to gather data autonomously for almost a year. During the four months of its high degassing rate, seismic activity was mostly expressed in the form of a long-period seismic tremor. In this study, a workflow based on the combination of back-projection, cluster analysis, and template-matching methods was developed to inspect the observed seismic signature. The processing of continuous seismic records yielded a catalog of individual long-period earthquakes that merges to constitute observed tremor-like signals. A catalog obtained using the back-projection detection algorithm consist of 1741 high-energy events. Cluster analysis revealed that a significant part of earthquakes in this catalog could be grouped into five families, which are sequentially organized in time. Utilizing stacked waveforms for each family in the template-matching detection resulted in the complementary catalog of 80,615 low-energy events. Such long-term occurrence of highly repetitive long-period earthquakes suggests a non-destructive mechanism that may correspond to several physical models. Ultimately, long-period earthquakes on Gorely represent a seismic signature of the magmatic system behaving in response to the high-pressure gases flowing from the decompressed magma chamber up to the volcano’s crater.