Paleomagnetic remanence direction is compared to the present-day geocentric axial dipole field direction at a site; if the remanent inclination coincides with today's expected field, this raises the possibility of a secondary viscous remanent magnetization (VRM) overprint rather than a primary thermoremanent record of the ancient field.
With X:Y:Z = 1:0:2, the horizontal component H = sqrt(X^2+Y^2) = 1 and Z = 2, giving tan(inclination) = Z/H = 2, so I ~=...
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