Enhanced seismic data conditioning and multi-attribute analysis through non-linear neural processing workflows has been applied to 3D seismic data over 215.10 km2 area of the Opunake prospect located in the south-eastern offshore Taranaki Basin. The present work aims to delineate faults and the related detail of structural features from the study area. Post-stack seismic data conditioning techniques such as dip-steering and structural filtering are applied to enhance the lateral continuity of seismic events and eliminate random noises from the data with the objective of improving the visibility of faults in the data volume. The conditioned data is then used to extract several attributes, such as similarity, dip variance, curvature, energy and frequency, that act as potential contributors for enhancing the fault visibility. A fully connected multilayer perceptron (MLP) network is developed to choose the proper combination of attributes for fault detection. These seismic attributes (known as the test datasets) are then trained at identified fault and non-fault locations using this network. The network comprises of 11, 7, and 2 nodes in the input layer, hidden layer and output layer, respectively. The neural training resulted in an overall minimum root mean square (RMS) misfit and misclassification (%) ranging from 0.54 to 0.67 and 18.67 to 10.42, respectively, between the trained and the test datasets. The neural training generates a fault probability attribute that produces an improved fault visibility capturing the minute details of the seismic volume as compared with the results of individual seismic attribute. Thus, the present work demonstrates an enhanced and robust workflow of fault prediction and visualisation for detail structural interpretation from 3D seismic data volume.

Gravity and magnetic studies have been carried out over a non-volcanic hot spring zone consisting of Atri and Tarabalo hot springs along the intracontinental Mahanadi rift basin to delineate the subsurface structures and to understand their effect on the geothermal activities over a stable continental region. Calculated gravity and magnetic anomaly maps unveil the presence of hot springs along Mahanadi fault. The four-layer subsurface configuration as observed using radially averaged power spectrum analysis and 3D Euler solutions of both gravity and magnetic data indicates occurrence of multi-phases sedimentation and tectonic events. 2D forward, 2D inverse, and 3D inverse residual gravity models have delineated high-density igneous intrusive bodies surrounded by comparatively less dense Khondalites and Charnockites rich altered zones. The sharp high to low density transition zones are identified as the regional Mahanadi fault. The India–Antarctica rifting, existence of two hot springs along the Mahanadi fault of the rifted basin, and similarity in water chemistry strongly indicates an interconnection between these two hot springs. Igneous intrusions and radiogenic element-rich metamorphosed shallow formations combinedly acting as the heat source. Deciphered altered zone, deeper intrusion and deeply connected regional fault along the hot springs confirmed that this regional fault is providing the major pathway for water circulation through radioactive element-rich altered zones while the local and shallow fractures connecting the Mahanadi fault feed the hot springs of the study area.

South Purulia Shear Zone (SPSZ) is an important area for the prospect of uranium mineralization and no detailed geophysical investigations have been carried out in this region. To delineate the subsurface structure in the present area, vertical electrical soundings using Schlumberger array and gravity survey were carried out along a profile perpendicular to the SPSZ. Apparent conductance in the subsurface revealed a possible connection from SPSZ to Raghunathpur. The gravity model reveals the presence of a northerly dipping low density zone (most likely the shear zone) extending up to Raghunathpur under a thin cover of granitic schist of Chotanagpur Granite Gneissic Complex (CGGC). The gravity model also depicts the depth of the zone of density low within this shear zone at~400 m near Raghunathpur village and this zone truncates with a steep slope. Integration of resistivity and gravity study revealed two possible contact zones within this low density zone in the subsurface at depth of 40 m and 200 m. Our study reveals a good correlation with previous studies in Raghunathpur area characterized by medium to high hydro-uranium anomaly. Thus the conducting zone coinciding with the low gravity anomaly is inferred to be a possible uranium mineralized zone.