Temporal Variations in Earthquake Triggering Mechanisms in the Tatun Volcano Group

The Tatun Volcano Group (TVG), adjacent to the densely populated Taipei metropolitan region in northern Taiwan, is an active volcanic system where a large number of earthquakes have been observed. Although the previous studies have reported that volcanic fluids exist beneath the surface, how these fluids change over time and influence local earthquakes has remained unclear. In this study, we examined more than 12,000 earthquakes recorded between 2014 and 2021 to explore how the behavior of earthquakes and the physical properties of the seismogenic zone vary with time. By analyzing patterns in frequency-magnitude distribution of earthquakes and seismic wave velocities within the seismogenic zone, we found that the triggering mechanisms for earthquakes in the TVG shift over time, possibly due to the varying influence of volcanic gases, hydrothermal waters, and stress. This study deciphers the dynamic nature of the TVG and improves our understanding of the volcanic risk near the Taipei metropolis.