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- Title
Experimental Multiblast Craters and Ejecta—Seismo‐Acoustics, Jet Characteristics, Craters, and Ejecta Deposits and Implications for Volcanic Explosions.
- Authors
Sonder, Ingo; Graettinger, Alison; Neilsen, Tracianne B.; Matoza, Robin S.; Taddeucci, Jacopo; Oppenheimer, Julie; Lev, Einat; Tsunematsu, Kae; Waite, Greg; Valentine, Greg A.; Befus, Kenneth S.
- Abstract
Blasting experiments were performed that investigate multiple explosions that occur in quick succession in unconsolidated ground and their effects on host material and atmosphere. Such processes are known to occur during phreatomagmatic eruptions at various depths, lateral locations, and energies. The experiments follow a multi‐instrument approach in order to observe phenomena in the atmosphere and in the ground, and measure the respective energy partitioning. The experiments show significant coupling of atmospheric (acoustic)‐ and ground (seismic) signal over a large range of (scaled) distances (30–330 m, 1–10 m J−1/3). The distribution of ejected material strongly depends on the sequence of how the explosions occur. The overall crater sizes are in the expected range of a maximum size for many explosions and a minimum for one explosion at a given lateral location. As previous research showed before, peak atmospheric over‐pressure decays exponentially with scaled depth. An exponential decay rate of d¯0=6.47×10−4mJ−1/3 ${\bar{d}}_{0}=6.47\times 1{0}^{-4}\,\mathrm{m}\,{\mathrm{J}}^{-1/3}$ was measured. At a scaled explosion depth of 4 × 10−3 m J−1/3 ca. 1% of the blast energy is responsible for the formation of the atmospheric pressure pulse; at a more shallow scaled depth of 2.75 × 10−3 m J−1/3 this ratio lies at ca. 5.5%–7.5%. A first order consideration of seismic energy estimates the sum of radiated airborne and seismic energy to be up to 20% of blast energy. Finally, the transient cavity formation during a blast leads to an effectively reduced explosion depth that was determined. Depth reductions of up to 65% were measured. Plain Language Summary: Blasting experiments using six successive explosions were performed. Explosives were detonated in unconsolidated ground material in four different geometric setups (linear and triangular). We monitored the experiments using geophysical instruments. The instruments measured explosive energy, and how much of that energy escapes the crater. The experiments help to understand volcanic (phreatomagmatic) and other subsurface explosive processes. Exact measurements of the resulting craters, together with known explosive energies allow the interpretation of real volcanic craters. The experimental results show initial time developments of crater sizes, which occurs on the order of 1 s for crater sizes of the order of 1 m. Up to 8% of an explosion's energy was detected as airborne signal. Up to 20% of the explosion's energy was detected as seismic (elastic) energy in the ground. Key Points: Airborne energy of an underground blast decays exponentially with scaled depth and is in agreement with previous measurementsTransient crater unloading leads to eruption at the surface from depths that were thought to be deep enough to be contained in the groundCrater sizes correlate with measured seismo‐acoustic and high‐frequency atmospheric signals
- Subjects
IMPACT craters; LUNAR craters; VOLCANIC craters; GEOPHYSICAL instruments; EXPLOSIONS; ATMOSPHERIC pressure; MEASURING instruments
- Publication
Journal of Geophysical Research. Solid Earth, 2022, Vol 127, Issue 8, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2022JB023952