Evidence for Middle to Late Pleistocene faulting within the northern Upper Rhine Graben (Alsace Plain, France).
Lemeille, F; Cushing, ME; Cotton, F; Grellet, B; Menillet, F; Audru, JC; Renardy, F; Flehoc, C.
COMPTES RENDUS DE L ACADEMIE DES SCIENCES SERIE II FASCICULE A-SCIENCES DE LA TERRE ET DES PLANETES, 328: (12) 839-846.
In the Upper Rhine Graben, trenches excavated across a 100-km-long geomorphic lineament show that normal faults vertically offset Late Cromerian formations (400-450 ka) by 16 m and Saalian formations (150-300 ka) by 6 m. The re-interpretation of seismic profiles corroborates the existence of normal faults cutting through the sedimentary cover. However, the connection between superficial observations and deep structures remains unclear. This analysis suggests that displacements were coseismic. An average recurrence interval of 25 000 years is obtained for a M = 6.0-6.5 magnitude earthquake (single metric displacement) with an inferred vertical deformation rate of 0.04 mm.yr(-1).