Strike standard deviation for shallow-dipping rock fracture sets

Herda, HHW

Hhw. Herda, Strike standard deviation for shallow-dipping rock fracture sets, ROCK MECH R, 32(4), 1999, pp. 241-255

6

INGLESE

Article

Geological Petroleum & Minig Engineering

ROCK MECHANICS AND ROCK ENGINEERING

0723-2632 → ACNP

32

4

1999

241 - 255

ISI

0723-2632(199910/12)32:4<241:SSDFSR>2.0.ZU;2-Q

The well-known problem that the observed strike of a shallow-dipping rock f racture can vary widely, even if one re-measures the strike in the same loc ation, is dealt with in this paper. The overall purpose of the paper is to place the statistical estimation of the strike confidence interval for shal low-dipping rock fracture sets on a sound foundation. We have made series o f strike measurements at each of various dips on a wooden laboratory "fract ure" to allow estimation of strike standard deviation at all shallow dips. This is accurate for smooth rock and serves as a lower bound estimate for r ock with a rougher surface. These estimates are used, along with two indepe ndent iterative statistical procedures, to reestimate the dip direction con fidence interval of an actual set of nineteen fractures. The dip direction confidence interval is more than three times as wide as the corresponding d ip confidence interval. This will be made visible in our transformed confid ence region plot for the mean pole.