Variability of the bottom-simulating reflector (BSR) and its association with tectonic structures in the Chilean margin between Arauco Gulf (37°S) and Valdivia (40°S) |
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Authors: | Cristián Rodrigo Antonio González-Fernández Emilio Vera |
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Institution: | 1.División Ciencias de la Tierra,Centro de Investigación Científica y de Educación Superior de Ensenada,Ensenada,Mexico;2.Departamento de Geofísica,Universidad de Chile,Santiago,Chile;3.Departamento Científico,Instituto Antártico Chileno,Punta Arenas,Chile |
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Abstract: | Multichannel seismic reflection data recorded between Arauco Gulf (37°S) and Valdivia (40°S), on the Chilean continental margin,
were processed and modeled to obtain seismic images and sub-surface models, in order to characterize the variability of the
bottom-simulating reflector (BSR), which is a geophysical marker for the presence of gas hydrates. The BSR is discontinuous
and interrupted by submarine valleys, canyons, as well as by faults or fractures. The BSR occurrence is more common south
of Mocha Island due to moderate slopes and greater organic matter contribution by rivers in that area. Tectonic uplift and
structural instability change the stability gas hydrate zone and consequently the BSR position, creating in some cases missing
or double BSRs. Our modeling supports the presence of gas hydrate above the BSR and free gas below it. Higher BSR amplitudes
support higher hydrate or free gas concentrations. In the study area, gas hydrate concentration is low (an average of 3.5%)
suggesting disseminated gas hydrate distribution within the sediments. Also higher BSR amplitudes are associated with thrust
faults in the accretionary prism, which serve as conduits for gas flow from deeper levels. This extra gas supply produces
a wider thickness of gas hydrates or free gas. |
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Keywords: | BSR Chilean margin Gas hydrates Reflection seismic Bathymetry Tectonic structures |
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