Improvement to resistivity pseudosection modelling by removal of near-surface inhomogeneity effects: application to a soil system in south Cameroon*     

Michel Ritz  Henri Robain  Evgeni Pervago  Yves Albouy  Christian Camerlynck  Marc Descloitres  Adama Mariko 《Geophysical Prospecting》1999,47(2):85-101

Near-surface inhomogeneities (NSIs) can lead to severe problems in the interpretation of apparent resistivity pseudosections because their effects significantly complicate the image aspect. In order to carry out a more efficient and reliable interpretation process, these problematic features should be removed from field data. We describe a filtering scheme using two-sided half-Schlumberger array data. The scheme was tested on synthetic data, generated from a simple 2D resistivity model contaminated by NSIs, and is shown to be suitable for eliminating such contaminations from apparent resistivity data. Furthermore, the original model without NSIs can be recovered satisfactorily from the inversion of filtered apparent resistivity data. The algorithm is also applied efficiently to a real data set collected at Nsimi, in southern Cameroon, along a 200-m shallow depth profile crossing a complex transitional zone. For this case, the filtering scheme provides accurate structural and behavioural interpretations of both the geometry of the major soil constituents and the groundwater partitioning.  相似文献   

Sedimentation in two Catalonian canyons,northwestern Mediterranean     

Henri Got  Daniel Jean Stanley 《Marine Geology》1974,16(5):M91-M100

The Cap Creus and Lacaze-Duthiers canyons, cut on the narrow subsiding margin off the eastern Pyrenees, play an important role in downslope sediment transport in the northwestern Mediterranean. This conclusion is based on an evaluation of the surficial sediment distribution patterns, cores, direct visual observations of the sea floor made in 24 submersible dives and tight-grid seismic survey data. Down-canyon sediment movement (mostly by slump and gravity flow mechanisms) since the end of the Pliocene has resulted in the formation of the Catalonia Fan at the base of the slope west of the Rhone Cone.  相似文献   

Brittle tectonism in relation to the Palaeogene evolution of the Thulean/NE Atlantic domain: a study in Ulster     

LAURENT GEOFFROY  FRANCOISE BERGERAT  JACQUES ANGELIER 《Geological Journal》1996,31(3):259-269

The tectonic effects of the Thulean mantle plume on the opening of the North Atlantic Ocean is still poorly understood. An analysis of the brittle deformation affecting the Late Cretaceous Chalk and Lower Tertiary igneous formations cropping out in Ulster (Northern Ireland), part of the Thulean Province, leads to the recognition of two tectonic phases. Each of these phases is characterized by different stress regimes with similar trends of the horizontal maximum principal stress σ_H. The first phase, syn-magmatic and dominated by NE–SW to ENE–WSW extension, occurred during the Palaeocene. It is followed by a second post-magmatic phase, characterized initially by a probably Eocene strike-slip to compressional palaeo-stress regime with σ₁ (=σ_H) trending NE–SW to NNE–SSW associated with the partial reactivation (as reverse faults) of normal faults formed during the first phase NE–SW extension. This episode is postdated by an Oligocene extension, with σ_H (=σ₂) still striking NNE–SSW/NE–SW, which reactivated Eocene strike-slip faults as nearly vertical dip-slip normal faults. This Palaeogene tectonic evolution is consistent with the tectonic evolution of similar age in western Scotland and in the Faeroe Islands. In particular, the post-magmatic NE–SW compression is here related to the ‘Faeroe compressive event’, which is related to the earliest stages of drift of the Greenland plate.  相似文献