Lava flows from sixteen sites at Gorely Volcano, Kamchatka were sampled. Initial analysis showed high within-site scatter for NRM specimen directions. Alternating field and thermal demagnetization of specimens showed single-component magnetization indicating that specimens had not moved or were not exposed to changes in the magnetic field during acquisition of a magnetic direction. Scatter is thought to be either due to movement of the specimen with respect to the magnetic field or change in the magnetic field with respect to the specimen. Four factors were found that would contribute to scatter in specimen directions. These are 1) cooling rate, 2) range of unblocking temperatures, 3) relative time of emplacement, and 4) how the specimen moved or was affected by changes in the magnetic field. Only two sites showed that scatter was due to movement of the specimen. It appears that scatter in other sites resulted from changes in the magnetic field generated from a magma-induced electrical current due to lava flowing in the earth’s magnetic field. These changes in the magnetic field are shown to have more affect on material sampled at the surface than on material sampled at depth because massive interiors of flows showed less dispersion in specimen directions than levees or pull-aparts.

Abstract We test two methods of 3-D acoustic source localization on volcanic explosions and small-scale jetting events at Karymsky Volcano, Kamchatka, Russia. Recent infrasound studies have provided evidence that volcanic jets produce low-frequency aerodynamic sound (jet noise) similar to that from man-made jet engines. For man-made jet noise, noise sources localize along the turbulent jet flow downstream of the nozzle. Discrimination of jet noise sources along the axis of a volcanic jet requires high resolution in the vertical dimension, which is very difficult to achieve with typical volcano-acoustic network geometries. At Karymsky Volcano, an eroded edifice (Dvor Caldera) adjacent to the active cone provided a platform for the deployment of five infrasound sensors in July 2012 with intra-network relief of ~ 600 m. The network was designed to target large-scale jetting, but unfortunately only small-scale jetting and explosions were recorded during the 12-day experiment. A novel 3-D inverse localization method, srcLoc, is tested and compared against a more common grid-search semblance technique. Simulations using synthetic signals show that srcLoc is capable of determining vertical solutions to within ± 150 m or better (for signal-to-noise ratios ≥ 1) for this network configuration. However, srcLoc locations for explosions and small-scale jetting at Karymsky Volcano show a persistent overestimation of source elevation and underestimation of sound speed. The semblance method provides more realistic source locations, likely because it uses a fixed, realistic sound speed of ~ 340 m/s. Explosion waveforms exhibit amplitude relationships and waveform distortion strikingly similar to those theorized by modeling studies of wave diffraction around the crater rim. We suggest that the delay of acoustic signals and apparent elevated source locations are due to raypaths altered by topography and/or crater diffraction effects, implying that topography in the vent region must be accounted for when attempting 3-D volcano acoustic source localization. Though the data presented here are insufficient to resolve small-scale jet noise sources, similar techniques may be successfully applied to large volcanic jets in the future.