Insights in nonlinear ground response in volcanic environments from distributed dynamic strain sensing

Area of Science:

• Geophysics
• Volcanology
• Seismology

Background:

• Volcanic environments exhibit frequent explosive activity and complex ground features.
• Ground response (GR) from volcanic explosions is poorly understood, unlike seismic input.
• Understanding explosion-induced GR is vital for near-surface material dynamics and hazard assessment.

Purpose of the Study:

• Investigate ground response (GR) generated by air-to-ground coupling of volcanic explosions.
• Analyze the relationship between volcanic explosions and near-surface ground behavior.
• Improve volcanic hazard assessments by understanding GR mechanisms.

Main Methods:

• Deployed a multi-parametric network including seismometers, infrasound sensors, and distributed dynamic strain sensing (DDSS) near Mt. Etna.
• Recorded over 65,000 volcanic explosions and analyzed high-frequency GR signals (10-50 Hz) within low-frequency explosions (0.7-4 Hz).
• Classified explosions by waveform similarity and analyzed GR signals using temporal and spatial dimensions, interpreting strain rate vs. pressure rate relationships.

Main Results:

• Observed high-frequency GR signals triggered by volcanic explosions in DDSS data.
• Identified amplification of high-frequency signals upon coupling into the ground.
• Interpreted ground behavior using linear elastic or hyperelastic models, suggesting nonlinear site amplification driven by particle interactions.

Conclusions:

• Volcanic explosions can induce significant ground response through air-to-ground coupling.
• Nonlinear site amplification, driven by mechanical particle interactions, is a key mechanism in volcanic GR.
• Further research is needed to definitively model near-surface ground behavior under volcanic explosion stress.