FA-71737 / Seismic magnitude estimation / Member archive

Scalar moment from moment tensor: off-diagonal multiplicity · case 02

Strike-slip and oblique mechanisms get Mw too small.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

mt = [Mrr, Mtt, Mpp, Mrt, Mrp, Mtp] mantissas; tensor = mantissa * 10^exponent dyne*cm. M0 = sqrt(sum of all nine squared elements / 2) (off-diagonals appear twice), converted to N*m (1e-7). Mw = 2/3 (log10 M0 - 9.1). Flag "non-deviatoric" when |trace| > 0.1 * M0 mantissa norm, else "deviatoric". Return [Mw rounded 0.01, flag].

Why this case matters

Global CMT catalogues report Mw from the scalar moment of the moment tensor.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
CMT 3	`[4.24, "deviatoric"]`	`[4.32, "deviatoric"]`	Failed

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