The implications of gas slug ascent in a stratified magma for acoustic and ground deformation source mechanisms in Strombolian eruptions

摘要: The interpretation of geophysical measurements at active volcanoes is vital for hazard assessment and understanding fundamental processes such as magma degassing. For Strombolian activity, interpretations are currently underpinned by first-order fluid dynamic models which give relatively straightforward relationships between signals gas flow. However, recent petrological high-speed video evidence has indicated the importance rheological stratification within conduit and, here, we show that under these conditions, break down. Using laboratory analogue experiments to represent a rheologically-stratified characterise distinct variations in shear stress exerted on upper sections flow tube pressures measured above liquid surface, during different degassing configurations. These signals, generated varying styles ascent, expansion burst, can reflect field infrasonic ground motion proximal vent. exhibit timescales trends qualitative agreement with near-vent inflation–deflation cycles identified Stromboli. Therefore, along uppermost may plausible source tilt, contributions should be considered deformation, usually attributed pressure sources only. same range produce experimental waveforms, even similar masses escape. data resembled waveforms acquired from vents Stromboli associated eruptive styles. Accurate signal style therefore requires detailed of: a) spatiotemporal rheology shallow conduit, b) geometry, well bubble overpressure volume.