THE BASEL 1356 EARTHQUAKE - WHICH FAULT PRODUCED IT

The 1356 Basel earthquake was the strongest event to have shaken NW Eu rope in the last thousand years. The peculiar location of this histori cal event makes it possible to relate it to normal faulting along the edges of the Rhine Graben, as well as to reverse faulting along the Ju ra frontal thrust or to fault reactivation within the Hercynian baseme nt. Alternate hypotheses are discussed and their implications compared taking into account available structural data and results of the morp hotectonic study performed in the epicentral area. This study combines field observations with the analysis of SPOT satellite imagery, aeria l photographs, and detailed topography. It is concluded that the Basel earthquake most probably reactivated a basement fault (reverse or wre nch fault) beneath the shallow-depth aseismic detachment that underlie s the Jura Mountains.