New Constraints on the Subsurface Geometry of the Eastern English Channel-Strait of Dover Area

Abstract:

The English Channel is characterized by a moderate seismicity and recent models predicted possible damaging tsunamis, endangering coastal populations and infrastructures (including Paluel, Penly and Gravelines nuclear power plants), as well as submarine infrastructures. To contribute preventing possible damage, a major effort to identify, characterize and map the complex fractures that cross the Weald-Artois Anticline is being carried out.

New datasets have been incorporated to the pre-existing database (formerly covering the Eastern English Channel and consisting of Sparker single channel seismic profiles – TREMOR project), with the aim of extending it northwards to reach the Dover Strait area. These new datasets consist of four additional Sparker single channel cruises (processed using RadExPro software – GEOBAS project) and an industrial multi-channel cruise.

Combining these datasets allowed to study the Weald-Artois Anticline under a new light, providing a general overview of its geometry on one hand, and allowing to zoom in the shallow structures in high resolution on the other. In particular, the high resolution of the Sparker seismic profiles allowed the accurate detection of faults, to calculate their offset and image the associated deformation, etc. as well as to pinpoint faults with evidences of neotectonism. In addition, abundant erosive surfaces and palaeochannels associated to faults and to lateral changes in material have been mapped.

Most faults identified in the seismic profiles show E-W trend, and comprise normal faults, reverse faults, and normal faults reactivated as reverse. The cartography of the faults also allowed to highlight the offshore continuity of well-known onshore tectonic structures. The great complexity of the fault system suggests that both shores of the Dover Strait are subject to greater geohazards than previously acknowledged. In addition, clues of the presence of gas in the sediments have been observed, thus endangering communication cables, pipe lines, wind farms and other coastal and submarine structures.

The combination of datasets with various resolutions allowed an unprecedented imaging of the geometry of the Anticline and its fault system, highlighting the most hazardous features and allowing a better management for present and future infrastructures.