Seismic pulses trapped between the ocean surface and the subbottom structure commonly observed in refraction profiling are modeled synthetically. The relative amplitudes of single- and double-bounce phases are used to study reflection coefficients and attenuation. The technique was applied to a 1-km-thick section of mature oceanic sediments located in the Bering Sea. The most surprising result is the lack of attenuation in the sediments which is estimated to have a Qα greater than 500 for pulses doinated by 10-Hz energy.