Indian Journal of Marine Sciences Vol. 35(3), September 2006, pp. 195-204 Source depth characterization of potential field data of Bay of Bengal by continuous wavelet transform Ashutosh Chamoli*, R. P. Srivastava & V. P. Dimri National Geophysical Research Institute, Hyderabad-500 007, India *[E-mail: chamoli_jp@rediffmail.com] Received 4 July 2005, revised 3 April 2006 Wavelet transform is an efficient technique to interpret the potential field data. The continuous wavelet transform is used to locate and characterize the source of the potential field by transferring the data into an auxiliary space. The technique has been tested on several synthetic source anomalies and applied to potential field data from Bay of Bengal. Using free air gravity and magnetic data the mean depth to causative sources indicates presence of lithospheric flexure at the central part of profile across 85°E ridge. Using free air gravity data, it is inferred that mean depth to causative sources decreases from west to east across 90°E ridge along MAN-01 profile which indicates increase of sediment thickness across the ridge from east to west. The technique gives mean depth of the causative sources without any a priori information which can be used as a initial model in any inversion algorithm. [Key words: Wavelet transform, potential field, source characterization, ridge, Bay of Bengal] Introduction Identification and characterization of the sources from the potential field data (e.g., magnetic and gravity) is ambiguous and thus, is a critical step in the formulation of initial model. Various techniques have been used to interpret potential field data; which are broadly categorized in two streams: one is “Forward modeling” and other is “inversion” 1,2 . Almost all techniques require a priori information of the source. Wavelet transform is one of recently developed method to interpret the source parameters 3 in an easy and effective way without any a priori information. Wavelet Transform (WT) transfers the original information carried by the potential field data into the wavelet transform space. A particular class of wavelets (Poisson group) allows for a geometric interpretation of the potential field anomaly in the wavelet transform domain 4 . Using the WT, the depth and location of the source can be easily estimated. Also, this technique doesn’t require long time series as in the case of Fourier transform and exhibits good spatial and temporal resolution. Here, this technique is used on synthetic potential field data and finally applied to free air gravity anomaly and magnetic anomaly across 85 0 E along MAN-03 and MAN-01 profile respectively and free air gravity anomaly across 90 0 E ridge along MAN-01 profile (Fig. 1) to decipher the ridge structure and nature of sedimentation along these ridges. Fig. 1—Bay of Bengal showing 85°E & 90°E ridge. Location of different profiles across 85°E & 90°E ridge are shown by 1, 2 and 3 where 1 shows profile from 13.06° N, 84.47° E to 13.06° N, 86.33° E of MAN-03 profile, 2 shows profile from station number 7 9000 to 11000 along MAN-01 profile and 3 shows profile from14.67°N, 89.65°E to 14.64°N, 91.78°E of MAN-01 profile. _____________ *Corresponding author Phone: +91-40-23434700 Fax: +91-40-23434561