Validation of Repetitive Volcanoseismic Signals in Aso Volcano, Japan With Distant Stations: Implications of Source Characterization and Remote Sensing in Uninstrumented Volcanoes

Abstract

Repetitive volcanoseismic signals, including very-long-period signals (VLP) and long-period signals (LP), provide a unique probe of fluid transport processes inside magmatic-plumbing system. While syneruptive signals are often detected and analyzed with regional or/and global seismic networks to retrieve eruption location and mechanism, repetitive noneruptive volcanoseismic signals are generally small, and they are typically detected with in situ stations near the volcanic edifices. Here, we show that repetitive VLP and synchronous deformation events in Aso volcano, Japan, can be detected in the high (15–30 s) and low (50–100 s) VLP bands, respectively, at seismic stations located ∼30–1,000 km away from their sources. Changes in the polarities, phases, and amplitudes of VLP and synchronous deformation events observed at the in situ stations can be verified by the seismic waves in the two VLP bands, respectively, at distant stations up to 150 km. Forward modeling of the amplitude decay in the two VLP bands against epicentral distance corroborates the source locations previously determined by the in situ data, whereas the joint data analysis of in situ and distant stations at high VLP band suggests the presence of single-force component (i.e., force/moment ratio of 10−4 m−1) in the source of VLPs. We advocate that not only can systematic data mining against established global and regional seismic networks potentially expand the detection capability of repetitive volcanoseismic signals backward in time when in situ observations were unavailable, but it could also substantially improve the detection and monitoring capacity in otherwise uninstrumented volcanoes, complementary to remote sensing of ground deformation.