Qualitative Crustal Interpretation of Central Indian Ocean Basin (CIOB) as Inferred from Gravity Data

Abstract

The objective of the present study is to make a crustal interpretation of the Central Indian Ocean Basin (CIOB) using qualitative techniques inferred from gravity data to delineate major crustal features such as fracture zones, ridges, and seamounts. This study area's free-air gravity anomaly data, which corresponds to short wavelengths (<20 km), is helpful for regional geophysical research. The Low-pass filtering method is used which is an application of the Fourier transform technique for qualitative analysis of free-air data which suppresses high-frequency noise or short-wavelength variations. Low-pass filters are implemented to the free-air gravity data of the study area. The free-air gravity anomaly data is qualitatively interpreted using various filtering techniques such as horizontal gradient, vertical gradient, upward and downward continuation, analytical signal, and tilt derivative technique to identify the nature of the anomaly corresponding to the major tectonic features of the study area.  The free-air gravity anomaly having positive trend from 9 - 15 mGal and negatively varies from 76 - 82 mGal for the observation height (H= 100 m). The analytical signal map shows a high analytical signal of 0.0027 mGal/m observed at shallow depths indicates tectonic features. The upward continuation data show that the attenuation of high wave number anomalies increases with increasing altitude and the downward continuation of the free air gravity anomaly grid data shows the change in anomalies with increasing observation altitude. The tilt derivative technique is used to find linear, sharp tectonic features corresponding to free-air gravity anomalies. This approach is used qualitatively to identify anomalous features at different frequencies, aiding in the interpretation of complex geological structures and boundaries using 2-D modelling.