Interpretation of gravity data over the 85 ºE ridge and Afanasy Nikitin

Abstract

The 85 ºE ridge is an enigmatic buried aseismic ridge having the peculiar negative gravity anomaly in the north and positive anomaly in the south. Different theories are proposed for the negative anomaly over the 85 ºE ridge. High-resolution two-dimensional satellite gravity data over 85 ºE ridge is interpreted using the spectral analysis method covering the area from 5ºS to 18 ºN. The area consists of the Afanasy Nikitin seamount, partially buried hills and the 85 ºE ridge. Twelve overlapping blocks of 3º3º are selected to calculate the depth of anomalous sources. The two layers of anomalous sources are observed for all blocks. The different depth values of causative sources are found for different portion of the 85 ºE ridge. The deeper depth values for each block are representing the crustal thickness. The maximum thickness of 25.6 km was found for block 10 covering the area between latitude 12 ºN to 15 ºN. The average crustal thickness decreases from north to south along 85º E ridge. The reason of negative free air gravity anomaly below the 85 ºE may be due to the depression in the Moho.