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sgr ms thesis - University of Maine

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to place a minimum size limit when measuring clasts (Blenkinsop, 1991; Clark<br />

and James, 2003; Barnett, 2004).<br />

CSD data are commonly presented with respect to 3-dimensional space. If<br />

an object is fractal in 2-dimensions, it is also fractal in 3-dimensions, and<br />

(5.5)<br />

This conversion is validated by the fact that D s refers to the line, surface, or<br />

space that dissects the object. An increase in Euclidean dimension requires the<br />

same increase in D s (e.g. Sammis et al., 1987). This conversion is justified for a<br />

breccia made <strong>of</strong> a homogeneous, isotropic material, but error can be introduced<br />

if this assumption is used on anisotropic materials (e.g. Barnett, 2004; Farris and<br />

Paterson, 2007). To reduce this potential error, outcrops with 3 dimensional<br />

exposures can be used. Clast distribution can also be expressed as a function <strong>of</strong><br />

clast frequency versus mass (e.g. Hartmann, 1969; Blenkinsop, 1991), or percent<br />

sample by weight versus diameter (see Schoutens, 1979), both <strong>of</strong> which are<br />

directly related to a 3-dimensional distribution. These results also pertain to<br />

power law distributions and therefore their slopes are proportional and can be<br />

converted to D s (Blenkinsop, 1991; Perfect, 1997).<br />

5.3.2. The Fractal Dimension-Brecciation Mechanism Link for Clast<br />

Size Distribution (CSD)<br />

Understanding the brecciation mechanism will provide important<br />

information on the mechanical response to subsurface volcanic eruption. As CSD<br />

results are a function <strong>of</strong> the self-similar manner by which fractures proliferate<br />

54

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