General information: Nearly 1,700 magnetic transects of the mid-ocean ridge system were used to estimate seafloor spreading rates for MORVEL. Selected from thousands of ship and airplane magnetic profiles collected during hundreds of ship cruises and airplane surveys since the 1960s, each of the 1696 transects used for the MORVEL study clearly samples either magnetic anomaly 1 (the Brunhes anomaly) or the anomaly 2A sequence and is therefore suitable for determining the average rate of seafloor opening over either the past 780,000 years or the past 3.16 million years.
The graphic below illustrates the cross-correlation procedure that we use to estimate a spreading rate for each magnetic profile. Synthetic, idealized magnetic profiles (shown by red lines) were created given the known sequence of magnetic reversals for the past few million years. The synthetically generated profiles were then compared systematically to the measured profiles (shown by black and blue lines) for a series of hypothetical spreading rates and reversal transition widths via a simple cross-correlation procedure. The procedure identifies the synthetic profile and hence seafloor spreading rate that best match either the edges of Anomaly 1 or the anomaly 2A sequence for the measured profile.
Plots similar to those below are available for nearly all of the 1600+ magnetic transects via the spreading center links that are located in the column to the left of this graphic.
C. DeMets, D. Argus, & R. Gordon