Plinian lapilli from the 1060 Common Era Glass Mountain rhyolitic eruption of Medicine Lake Volcano, California, were collected and analyzed for vesicularity and permeability. A subset of the samples were deformed at a temperature of 975°, under shear and normal stress, and postdeformation porosities and permeabilities were measured. Almost all undeformed samples fall within a narrow range of vesicularity (0.7–0.9), encompassing permeabilities between approximately 10−15 m2 and 10−10 m2. A percolation threshold of approximately 0.7 is required to fit the data by a power law, whereas a percolation threshold of approximately 0.5 is estimated by fitting connected and total vesicularity using percolation modeling. The Glass Mountain samples completely overlap with a range of explosively erupted silicic samples, and it remains unclear whether the erupting magmas became permeable at porosities of approximately 0.7 or at lower values. Sample deformation resulted in compaction and vesicle connectivity either increased or decreased. At small strains permeability of some samples increased, but at higher strains permeability decreased. Samples remain permeable down to vesicularities of less than 0.2, consistent with a potential hysteresis in permeability‐porosity between expansion (vesiculation) and compaction (outgassing). We attribute this to retention of vesicle interconnectivity, albeit at reduced vesicle size, as well as bubble coalescence during shear deformation. We provide an equation that approximates the change in permeability during compaction. Based on a comparison with data from effusively erupted silicic samples, we propose that this equation can be used to model the change in permeability during compaction of effusively erupting magmas.

Seismic tomography is used to infer compositional variations and environmental conditions in active subduction zones. In some regions, low P-wave ( )V p and S-wave ( ) V s velocities and high V V p s

International audienceUnderstanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental Physics, but also for geophysical processes and construction on sediments or granular soils in areas potentially affected by earthquakes. While the penetration of intruders in two dimensional (2D) laboratory granular beds can be followed using video recording, it is useless in three dimensional (3D) beds of non-transparent materials such as common sand. Here we propose a method to quantify the sink dynamics of an intruder into laterally shaken granular beds based on the temporal correlations between the signals from a reference accelerometer fixed to the shaken granular bed, and a probe accelerometer deployed inside the intruder. Due to its analogy with the working principle of a lock in amplifier, we call this technique Lock in accelerometry (LIA). During Earthquakes, some soils can lose their ability to sustain shear and deform, causing subsidence and sometimes substantial building damage due to deformation or tumblin

The elastic waves produced by "typical" small magnitude earthquakes (M ω between 1 and 3) have a recorded frequency range between 1 and 30 Hz (Shelly et al., 2007). In contrast, the families of earthquakes known as very low-frequency earthquakes (VLFEs) (Ide et al., 2007;Obara & Kato, 2016) and low-frequency earthquakes (LFEs) (Obara, 2002;Rogers & Dragert, 2003;Schwartz & Rokosky, 2007) are depleted in high frequencies when compared to small "typical" earthquakes of similar magnitudes (Figure 1a). The frequencies depleted in VLFEs and LFEs are generally observed for the S-waves and occur above approximately 0.1 and 2-8 Hz, respectively (Bostock et al., 2015;Farge et al., 2020;Supino et al., 2020). These events have lower corner frequencies than typical earthquakes of the same size, which marks the onset of a rapid decrease in the amplitude spectra and indicates a depletion of high frequencies (Figure 1a). The corner frequency is inversely proportional to rupture duration. Given this relationship, it is hypothesized that rupture and slip are slower for VLFEs and LFEs than for typical earthquakes of the same size, because their lower corner frequencies imply longer duration. The most common explanation for this observation is that the sources of VLFEs and LFEs are governed by different rupture and slip physics than typical earthquakes (

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