1887

Abstract

Summary

Identification of zones vulnerable to subsidence is a critical task for planning protection actions in deltas. This identification mainly relies on Holocene sediments characterization. Geophysical studies have been carried out in the Ebro Delta (Spain) with this objective. In this paper we focus in two borehole sites where several surface geophysical techniques have been applied to find geophysical patterns that help to characterize the Holocene sequence. The applied methods are: active and passive seismic (H/V and array), electrical resistivity tomography (ERT) and audiomagnetotellurics methods (AMT). Shear wave velocity from active seismic can help to discriminate between surficial sediment facies. Combining this method with array measurements allows obtaining a complete Vs profile for the Holocene sediments. Another targets included in delta sediments characterization are depth and thickness of the Prodelta marine clays due to their particular geotechnical characteristics. These sediments are the origin of dominant higher modes of surface waves which help to their identification. Finally, ERT and AMT results show a resistivity change that can be related to the transition between Holocene sediments to Pleistocene gravels. This contact also produces a second peak in H/V spectral ratio that can be used to estimate the depth of Holocene delta base.

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/content/papers/10.3997/2214-4609.201701975
2017-09-03
2022-06-29
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References

  1. Benjumea, B., Gabàs, A., Macau, A., Bellmunt, F., Figueras, S., Vilà, M., & Pi, R.
    [2016]. Combination of Geophysical Technques to Characterize Sediments (Ebro Delta, Spain). In Near Surface Geoscience 2016-22nd European Meeting of Environmental and Engineering Geophysics.
    [Google Scholar]
  2. LokeM.H. and Barker, R.D.
    [1996]. Rapid Least-Squares Inversion of Apparent Resistivity Pseudosections Using a Quasi-Newton Method. Geophysical Prospecting, 44(1):131–152.
    [Google Scholar]
  3. Macau, A., Benjumea, B., Gabàs, A., Figueras, S., and Vilà, M.
    [2015]. The Effect of Shallow Quaternary Deposits on the Shape of the H/V Spectral Ratio. Surveys in Geophysics, 36(1), 185–208.
    [Google Scholar]
  4. O’Neill, A., & Matsuoka, T.
    [2005]. Dominant higher surface-wave modes and possible inversion pitfalls. Journal of Environmental & Engineering Geophysics, 10(2), 185–201
    [Google Scholar]
  5. Somoza, L., and Rodríguez-Santalla, I.
    [2014]. Geology and geomorphological evolution of the Ebro River Delta. In Landscapes and Landforms of Spain (pp. 213–227). Springer Netherlands.
    [Google Scholar]
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