sgr ms thesis - University of Maine

Explosion breccias are formed by an instantaneous localized volume
expansion and resulting shockwave of released elastic energy (Schoutens, 1979;
Ivanov et al., 2005; Goto et al., 2001; Lorenz and Kurszlaukis, 2006; Nikolaevskiy
et al., 2006; Sanchidrian, 2007). Brecciation intensity decreases with distance
from the point source of explosion. These breccias tend to have a high gradient
of increasing particle frequency with decreasing particle radius (D s ≥2.5;
Schoutens, 1979; Barnett, 2004; Bjork et al., 2009). This is the result of a chaotic
proliferation of fractures at a finer scale. As opposed to hydraulic brecciation,
explosive fragmentation is driven predominantly by the power of the explosion
and the bulk strength of the rock (Grady and Kipp, 1987; Jebrak, 1997). Higher
D s values correlate with high power mechanisms because there is skewed
preference for small fracture proliferations during high energy fracture events
(Turcotte, 1986; Jebrak, 1997).
Bedrock anisotropy is an additional variable that can lead to relatively nonuniform
and unexpected fracture patterns when compared to fractures in
homogeneous rock. The fracture patterns in the rock are dominated by inherent
weaknesses, preferring the widening of existent fractures as opposed to the
proliferation of new fractures (Takashi, 2008). D s would be partially influenced by
structural anisotropy.
5.3.3. Clast Boundary Shape
Boundary shape is another natural expression of self-similar patterns. A
fragment’s boundaries appear to be fractal in that the process by which they are
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