FA-71639 / Seismic magnitude estimation / Member archive

GNSS peak ground displacement magnitude: magnitude inversion · case 04

PGD magnitudes are several units too high and distance-independent.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

obs are [PGD in m, epicentral km]. Per station PGD in cm, R = hypocentral distance; skip PGD < 2 cm or R > 1000 km. log10(PGD) = A + B M + C M log10 R with A=-4.434, B=1.047, C=-0.138, solved for M. Return [mean M rounded 0.01, stations used] or None.

Why this case matters

GNSS PGD magnitudes do not saturate for great earthquakes in early warning.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
GNSS set 11	`[4.37, 3]`	`[6.34, 3]`	Failed

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