MEASUREMENT METHOD

Parameter which was minimised in the grid search over phi and dt values. Either the smaller of the two eigenvalues in the covariance matrix calculated from the particle motion, (Eigenvalue Method) or the energy on the transverse component, (Transverse Energy Method).

ERROR METHOD

Method used to calculate errors. Either the methodology of Silver and Chan, (1991), or the bootstrapping method of Sandvol and Hearn (1994).

For the Silver and Chan method, we report the standard deviation, calulated from the bounding rectangle of the confince intervals. See:

Silver, P. and W. Chan (1991). Shear wave splitting and subcontinental mantle deformation, J. Geophys. Res. 96, 16429-16454.

For the Bootstrapping method we report the 16th and 84th percentile from the distribution of polarisation angle and lag time values. (This bounds 68% of the data, equivalent to one standard deviation reported using the Silver and Chan method). See:

Sandvol, E. and T. Hearn (1994). Bootstrapping Shear-Wave Splitting Errors, BSSA, Vol. 84, 1971-1977.

Note: Results where initial values do not lie wihin the 16th and 84th percentiles are automatically ignored.

ANGLE ERROR

Maximum error accepted in polarisation angle, using either error method described above. (For the bootstrapping method, where the data can be skewed, we use the half the difference of the maximum and minimum values.)

LAG ERROR

Maximum error accepted in lag value, using either error method described above. (For the bootstrapping method, where the data can be skewed, we use the half the difference of the maximum and minimum values.)

MAXIMUM LAG

Maximum lag value accepted in results. Null or noisy data, with little to constrain lag values, can often incline towards higher measurements. These can be ignored using this method.

ORIGINAL EIGENVALUE RATIO METHOD

Ratio of eigenvalues, (min/max), calculated from original traces. Values below this threshold are potential null measurements.

CORRECTED EIGENVALUE RATIO METHOD

Ratio of eigenvalues, (min/max), calculated from corrected traces. Results with values above this threshold are too noisy to be considered reliable results.

NULL MEASUREMENTS

Values excluded on the basis of the 'O' method (original eigenvalue ratio method) are considered potential null measurements, especially in the absence of the 'A' or 'C' flags. To include these in your plots as yellow squares, check this box.