Formation of magnetic anomaly patterns by dyke injection

A Monte Carlo method is used to simulate the linear magnetic anomalies that are observed over much of the mid-oceanic ridge system. These anomalies are believed to be caused by crustal spreading from the ridge center coupled with reversals of the earth's magnetic field. Magnetized dykes are injected into the crust at distances from the ridge that are normally distributed. By varying the standard deviation of the normal distribution, changes can be produced in the simulated anomalies. The simulated anomalies are compared with observed anomalies to determine what this standard deviation should be. It is concluded that the standard deviation is less than 3 km and that most of the material responsible for the magnetic anomalies is injected into the crust within a band 12 km wide or less. It is also concluded that the central anomaly is larger than the flanking anomalies because of a change in the intensity of the earth's magnetic field and/or because of a demagnetization process.