Active Normal Faulting in the Upper Rhine Graben and Paleoseismic Identification of the 1356 Basel Earthquake
Mustapha Meghraoui,1*
Bertrand Delouis,2
Matthieu Ferry,2
Domenico Giardini,2
Peter Huggenberger,3
Ina Spottke,3
Michel Granet1
We have identified an active normal fault in the
epicentral area of the Basel (Switzerland) earthquake of 18 October
1356, the largest historical seismic event in central Europe. The event of 1356 and two prehistoric events have been characterized on the fault
with geomorphological analysis, geophysical prospecting, and trenching.
Carbon-14 dating indicates that the youngest event occurred in the
interval 610 to 1475 A.D. and may correspond to the 1356 Basel
earthquake. The occurrence of the three earthquakes induced a total of
1.8 meters of vertical displacement in the past 8500 years for a mean
uplift rate of 0.21 millimeters per year. These successive ruptures on
the normal fault indicate the potential for strong ground movements in
the Basel region and should be taken into account to refine the seismic
hazard estimates along the Rhine graben.
1 Ecole et Observatoire des Sciences de la
Terre-Institut de Physique de Globe (EOST-IPAS), 5 rue René
Descartes, 67084 Strasbourg, France.
2 Institut of
Geophysics, Department of Seismology and Geodynamics,
Eidgenössische Technische Hochschule, Hoenggerberg, CH-8093,
Zurich, Switzerland.
3 Geologisch-Paläontologisches Institut,
Universität Basel, Bernoullistrasse 16, CH-4056, Switzerland.
*
To whom correspondence should be addressed. E-mail:
mustapha{at}eost.u-strasbg.fr
