A multidisciplinary study of a slow-slipping fault for seismic hazard assessment: the example of the Middle Durance Fault (SE France) |
| |
| Authors: | E M Cushing O Bellier S Nechtschein M Sébrier A Lomax Ph Volant P Dervin P Guignard L Bove |
| |
| Institution: | IRSN, Institut de Radioprotection et de SûretéNucléaire, B.P. 17, F-92 262 Fontenay-aux-Roses Cedex, France;CEREGE –UMR CNRS 6635 –UniversitéPaul Cézanne Aix-Marseille 13545 Aix-en-Provence Cedex 4, France;UniversitéPierre et Marie Curie –Paris VI Laboratoire de Tectonique –CNRS UMR 7072, F-75252 Paris Cedex 05, France;A. Lomax Scientific, 161 Allee du Micocoulier, 06370 Mouans-Sartoux, France;Toreador Energy SCS, 9 rue Scribe 75009 Paris, France |
| |
| Abstract: | Assessing seismic hazard in continental interiors is difficult because these regions are characterized by low strain rates and may be struck by infrequent destructive earthquakes. In this paper, we provide an example showing that interpretations of seismic cross sections combined with other kinds of studies such as analysis of microseismicity allow the whole seismogenic source area to be imaged in this type of region. The Middle Durance Fault (MDF) is an 80-km-long fault system located southeastern France that has a moderate but regular seismicity and some palaeoseismic evidence for larger events. It behaves as an oblique ramp with a left-lateral-reverse fault slip and has a low strain rate. MDF is one of the rare slow active fault system monitored by a dedicated dense velocimetric short period network. This study showed a fault system segmented in map and cross section views which consists of staircase basement faults topped by listric faults ramping off Triassic evaporitic beds. Seismic sections allowed the construction of a 3-D structural model used for accurate location of microseismicity. Southern part of MDF is mainly active in the sedimentary cover. In its northern part and in Alpine foreland, seismicity deeper than 8 km was also recorded meaning active faults within the crust cannot be excluded. Seismogenic potential of MDF was roughly assessed. Resulting source sizes and estimated slip rates imply that the magnitude upper limit ranges from 6.0 to 6.5 with a return period of a few thousand years. The present study shows that the coupling between 3-D fault geometry imaging and accurate location of microseismicity provides a robust approach to analyse active fault sources and consequently a more refined seismic hazard assessment. |
| |
| Keywords: | Palaeoseismology Seismicity and tectonics Continental neotectonics Dynamics and mechanics of faulting Europe |
|
|
