A Bottom Simulating Reflector (BSR) is a seismic feature closely related to marine gas hydrate as it is usually regarded as the seismic response of the base of the gas hydrate stability zone in seismic profiles. BSRs are widely distributed in the Makran accretionary wedge, and double BSRs are observed at some locations. Double BSRs usually appear on seismic profiles as two layers of BSRs located at distinct depths but with large lateral seismic amplitude variations. Based on the multi-channel seismic reflection data acquired over the Makran accretionary wedge, this work studies the origin of the double BSR in the Makran accretionary wedge and its association with fluid escape events. Our modeling suggests that double BSRs correspond to both the paleo-seafloor and modern seafloor caused by late sedimentary activities. Also, the residual paleo-BSR migrates upward due to the increase in local geothermal gradient caused by diapirs and gas chimney thermal fluids.

In this paper, the physical and practical significance of seabed reflection coefficient are studied based on the seismic convolution model, which reveals that high frequency signal is sensitive to the acoustic impedance changing. Then based on the seismic data acquired in the west coast of Taiwan Strait used for case study, the seabed reflection coefficient is calculated in the light of sound pressure level and seabed reflected wave. In comparison with the results of geological sampling and analysis, the overall trend of fine particles correspond to lower reflection coefficient and coarse particles correspond to greater reflection coefficient. In addition, the abnormal values of the calculated reflection coefficient could indicate some abnormal phenomena at or near the seabed, which could also be identified from the seismic profile. In brief, the seabed reflection coefficient derived from high frequency seismic data could be used for studying the modern marine sedimentary environment. The reflection intensity might be a good indicator of hydrodynamics of sedimentation.