Dictionary:ABC method

{{#category_index:A|ABC method}} A method of computing refractor depth based on refracted arrivals from sources near the surface. Especially used for determinations of weathering thickness from sources above the base of the weathering. See Figure A-1. The weathering time t_W is sometimes multiplied by a ‘‘k-factor’’ to give the vertical weathering time:

$t_{v}=kt_{w}={\frac {(t_{w}V_{1})}{({\sqrt {V_{1}^{2}-V_{2}^{2}}})}}$

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  FIG. A-1. ABC weathering method. Weathering time t_W below B is t_w=(t_AB+t_BC–t_AC)/2 where t_AB=surface-to-surface time from A to B (obtained by adding the uphole time to the first-break time), etc.