The attenuation structure (1/Q) in the sediments of the Cmarcik Basin of the Marmara Sea was estimated from the raw shot data of a multi-channel seismic reflection experiment using a wavelet modeling technique. The estimated attenuation, called the effective-Q is the sum of the inelastic absorption and the apparent attenuation. The estimated effective-Q values along the north-south trending seismic profiles are interpreted together with their time-migrated seismic sections. There are several local minima in the boundary separating the low (< 100) and high (greater than or equal to 100) effective-Q values. The relation between the low effective-Q structure arid fault is tested across a known active fault on the western edge of Izmit Bay in the eastern Marmara Sea. It is found that there is a correlation between the local minima of the effective-Q values and the faults. (C) 2002 Elsevier Science B.V. Ail nights reserved.