Assessing data quality in fault slip analysis: Simulations using random faults

Orife, Tobore and Lisle, Richard 2006. Assessing data quality in fault slip analysis: Simulations using random faults. Journal of Structural Geology 28 (6) , pp. 952-956. 10.1016/j.jsg.2006.03.005

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Abstract

Fault-slip analysis assumes that measured slip lineations on faults represent the direction of maximum resolved stress produced by single homogenous state of stress. To devise criteria for recognising natural data that do not comply with this assumption, the performance of fault-slip methods is examined when used to analyse unsuitable data; namely, faults and slip lineations with randomly chosen orientations. Data quality is often judged by examining the average discrepancy between the orientation of actual slip lineation on each fault and the lineation theoretically predicted from the best-fit tensor. In this work, however, it is found that random faults also yield small angular misfits in conditions where eight or less faults are used. This criterion is therefore only useful for large samples of faults. Another test of data quality is to use the existence of tensors that are compatible with a given data set. However, even for random data, tensors can be found that are capable of explaining the lineation orientations. For example, the existence of compatible stress orientations deduced from the right dihedra method is no proof that the data meet the assumptions of the method. The probability of finding such tensors depends on the tolerance used when assessing fit, and the total number of trial tensors used. A more useful check on data quality is the proportion of trial tensors that fit data sets. For random data this proportion is found to decrease rapidly with sample size. For sample sizes greater than five faults, the expected proportion of tensors fitting is very small (<1%). Statistical tests are proposed. This study emphasises the dangers of palaeostress determinations from small numbers of faults. All of the tests of quality increase in power as the number of faults in the sample increases. It is concluded that stress estimates based on eight or less faults should be treated with grave suspicion.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
Uncontrolled Keywords:	Fault slip analysis; Statistics; Dynamics; Palaeostress
Publisher:	Elsevier
ISSN:	0191-8141
Last Modified:	04 Jun 2017 02:10
URI:	https://orca.cardiff.ac.uk/id/eprint/10398

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