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Marine Geophysical Researches

, Volume 30, Issue 1, pp 1–19 | Cite as

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)

  • Cristián Rodrigo
  • Antonio González-Fernández
  • Emilio Vera
Original Research Paper

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.

Keywords

BSR Chilean margin Gas hydrates Reflection seismic Bathymetry Tectonic structures 

Notes

Acknowledgments

We thank the support of the Chilean FONDEF project D04I1111 (Hidratos de gas submarinos, análisis de los escenarios de exploración y producción como contribución a la matriz energética nacional), Centro de Investigación Científica y de Educación Superior de Ensenada of Mexico (CICESE), Instituto Antártico Chileno (INACH), and the Hydrographic and Oceanographic Service of the Chilean Navy (SHOA). We also thank the Federal Institute for Geosciences and Natural Resources of Germany (BGR) for releasing the SPOC seismic data. Constructive observations and valuable opinions from Nina Kukowski and Peter Clift are appreciated, and also the comments from an anonymous referee.

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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Cristián Rodrigo
    • 1
    • 3
  • Antonio González-Fernández
    • 1
  • Emilio Vera
    • 2
  1. 1.División Ciencias de la TierraCentro de Investigación Científica y de Educación Superior de EnsenadaEnsenadaMexico
  2. 2.Departamento de GeofísicaUniversidad de ChileSantiagoChile
  3. 3.Departamento CientíficoInstituto Antártico ChilenoPunta ArenasChile

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