Experimental multiblast craters and ejecta - seismo-acoustics, jet
characteristics, craters, and ejecta deposits and implications for
volcanic explosions
Abstract
Blasting experiments were performed that investigate multiple explosions
that occur in quick succession in the ground and their effects on host
material and atmosphere. Such processes are known to occur during
volcanic 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 mJ^-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. The experiments also show that peak
atmospheric over-pressure decays exponentially with scaled depth at a
rate of d0 = 6.47×10-4 mJ-1/3; at a scaled explosion depth of 4×10-3
mJ-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 mJ-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.