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Unraveling Dynamical Influences on Volcanic Structures Through Seismic Signatures

Description: 

Detecting the transition from volcanic quiescence to unrest is a crucial but challenging task for volcano monitoring agencies. Using insights drawn from continuous seismic records, this study explores the long-term dynamics of two volcanoes with the goal of tracking the transition to renewed activity. First, we investigate seismic velocity changes (dv/v) over time through cross-correlation of ambient seismic noise using the MSNoise package [Lecocq et al. 2014; https://doi.org/10.1785/0220130073] with the Wavelet Cross-Spectrum method [Mao et al. 2020; https://doi.org/10.1093/gji/ggz495]. Second, we examine the kernel sensitivity of the surface waves to identify potential depths related to dv/v changes based on wave frequency and realistic velocity models. Finally, we estimate the associated seismic attenuation to identify subsurface stress changes over time.

By applying these methods to our case studies, we observe and compare different behaviors, which highlights the importance of continuous monitoring of subsurface variations over time. For instance, we found a decreasing trend of dv/v at around 2 km depth since August 2021 beneath Askja volcano (Iceland), coinciding with an uplift of up to 65 cm by September 2023 and with an increased seismicity rate. The sudden shift in the trend of dv/v contrasts with the gradual long-term deflation that has been observed in the last few decades.

The 2016 Kumamoto earthquake impacted the Aso volcano in Japan, causing a decrease in dv/v of 0.5%. The seismic velocity changes suggest a healing process initiated post-earthquake, which stopped 6 months after with Aso eruption (0.3% dv/v drop).

During the summer of 2021, there was seismic unrest at Gareloi (Alaska) [AVO website, 2005; https://avo.alaska.edu]. This unrest was detected with the appearance of tremors in addition to persistent long-period activity. The dv/v result confirmed this observation with a 1% drop around 3 km depth. This helps to establish a baseline for normal volcanic behavior and contextualize observations, with the aim of characterizing the seismic signatures and changes associated with volcanic unrest.

Session: Multidisciplinary Approaches for Volcanic Eruption Forecasting [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Laure

Student Presenter: Yes

Invited Presentation: 

Authors