10:45 〜 12:15
[SVC29-P07] Episodic transport of discrete magma batches beneath Aso volcano: Validation of repetitive volcano-seismic Signals beneath Aso volcano with distant stations
キーワード：ASO, VLP, Magma ascent and storage
Magma ascent, storage, and discharge in the trans-crustal magmatic system are keys to long-term volcanic output and short-term eruption dynamics. How a distinct magma batch transports from a deep reservoir(s) to a pre-eruptive storage pool with eruptible magma remains elusive. Repetitive volcanoseismic signals, including very-long-period signals (VLP), provide a unique probe of fluid transport processes inside magmatic-plumbing system. Niu and Song (2021) recently showed that repetitive very-long-period signals (VLPs) beneath the Aso volcano are preceded by a short-lived (~50-100 s), synchronous deformation event ~3 km apart from the VLP source. Source mechanism of a major volumetric component (~50-440 m3 per event) and a minor low-angle normal-fault component, together with petrological evidence, suggest episodic transport of discrete magma batches from an over-pressured chamber roof to a pre-eruptive storage pool near the brittle-ductile transition regime.
Since these repetitive noneruptive volcanoseismic signals are generally small, they are typically detected with in situ stations near the volcanic edifices. Here we further demonstrate that repetitive VLP and synchronous deformation events in Aso volcano 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 points to the presence of single-force component (i.e., force/moment ratio of 10-4 m-1) in the source of VLPs that are previously unconstrained.
Since these repetitive noneruptive volcanoseismic signals are generally small, they are typically detected with in situ stations near the volcanic edifices. Here we further demonstrate that repetitive VLP and synchronous deformation events in Aso volcano 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 points to the presence of single-force component (i.e., force/moment ratio of 10-4 m-1) in the source of VLPs that are previously unconstrained.