Fault activity in the epicentral area of the 1580 Dover Strait (Pas-de-Calais) earthquake (northwestern Europe)

Abstract

S U M M A R YOn 1580 April 6 one of the most destructive earthquakes of northwestern Europe took place in the Dover Strait (Pas de Calais). The epicentre of this seismic event, the magnitude of which is estimated to have been about 6.0, has been located in the offshore continuation of the North Artois shear zone, a major Variscan tectonic structure that traverses the Dover Strait. The location of this and two other moderate magnitude historical earthquakes in the Dover Strait suggests that the North Artois shear zone or some of its fault segments may be presently active. In order to investigate the possible fault activity in the epicentral area of the AD 1580 earthquake, we have gathered a large set of bathymetric and seismic-reflection data covering the almost-entire width of the Dover Strait. These data have revealed a broad structural zone comprising several subparallel WNW-ESE trending faults and folds, some of them significantly offsetting the Cretaceous bedrock. The geophysical investigation has also shown some indication of possible Quaternary fault activity. However, this activity only appears to have affected the lowermost layers of the sediment infilling Middle Pleistocene palaeobasins. This indicates that, if these faults have been active since Middle Pleistocene, their slip rates must have been very low. Hence, the AD 1580 earthquake appears to be a very infrequent event in the Dover Strait, representing a good example of the moderate magnitude earthquakes that sometimes occur in plate interiors on faults with unknown historical seismicity.

Two-stage opening of the Dover Strait and the origin of island Britain

“…Similarly, a seismic profile across Fosse B shows that while its north-eastern margin is eroded into the flank of a fault-controlled monocline, the overall geometry of Fosse B is not structurally controlled (Fig. 3)32. We conclude that pre-existing structures, although influencing Fosses geometry, are not a primary control on their formation.…”

“…Similarly, pre-existing structures influence but do not govern Fosses formation. Fosse A is eroded along a WNW–ESE-oriented fault zone3132, which it cross-cuts and which constrains its geometry as indicated by its WNW–ESE-oriented elongate geometry. By contrast, Fosse D is eroded into horizontally stratified bedrock and is not associated with any structures (Figs 4 and 5).…”

A new paradigm for large earthquakes in stable continental plate interiors

“…Therefore, most of the seismic energy release since the Middle Ages in this part of Western Europe occurred outside the Roer Valley Graben, despite the graben's dominance in Western European seismic activity over the Quaternary. A recent offshore survey in the epicentral area of the 1580 Dover Strait earthquake showed no evidence for persistent faulting during the Quaternary [ Garcia‐Moreno et al , ]. Similarly, the Hercynian‐age Hockai fault activated during the 1692 Verviers earthquake shows no evidence for previous events in the Quaternary [ Lecocq et al , ].…”

Middle–Late Pleistocene landscape evolution of the Dover Strait inferred from buried and submerged erosional landforms

“…A series of WNW-striking Cretaceous and Jurassic sedimentary formations outcrop on the seafloor of the Dover Strait ( Figure 2). These geological formations are folded into the regional Weald-Artois anticline ( Figure 2) and locally deformed and offset by the North Artois Shear Zone (Figures 4 and 5;García-Moreno et al, 2015). In this paper, we refer to pre-Quaternary formations as bedrock.…”

“…Formations (see Table 1 for details). Recognising and mapping these units across the Strait itself relies largely on their geophysical expression (García-Moreno et al, 2015). For example, the base of the Holywell Nodular Chalk Formation and the Hythe Formation are well marked in the bathymetry, forming, respectively, a 1-3 m high scarp and 5-10 m high ridge ( Figure 5b).…”