Sismiques_événements

The seismic events

During the sedimentation of the chalk, earthquakes occurred and some of them were violent enough to engender what we call séismites.
We indicate under the name of séismite (Seilacher, on 1969, sometimes still sismite) sedimentary coats presenting structures of deformations in situ led
By a seismic shock. A big variety of structures can be engendered according to the consolidation and the composition of the sediment.
Most of the séismites described in the geologic literature interest detrital sediments, particularly alternations sand-clay for which he is convenient to analyze the geometry. In a sediment of tint homogeneous as the chalk, the possible seismic structures are more difficult to spot, except when in the chalk fit levels of flint. Chalks in the SW of the syncline of Ailly are in this case and it is mainly in this region that séismites is described here.
Here is an example of séismite, in him E of Veules-les-Roses and the corresponding interpretation:


See the event paléosismique éoconiacien of Eletot
See the event paléosismique of the end of average Santonien (Veules-les-Roses), video B. Hoyez

A model of the séismites of the chalk

Certain number of structures testifying of the action of an earthquake is specific in the chalk. They were described to Eletot or to Veules-les-Roses and can be gathered on this plan. Other structures as boudinage and synthetic break in rhombuses of flints can be mentioned.

Model of the séismites of the chalk

List of seismic events

Santonien superior

Santonien means

Santonien inferior

Coniacien superior

Coniacien means

Coniacien inferior

Turonien superior

Cénomanien means