In situ stress data from the Jura Mountains — new results and interpretation

Abstract

Recently completed in situ stress measurements using the borehole slotter at 33 new test sites within the Swiss and French Jura Mountains are presented. When combined with previously published stress data, these new measurements allow a detailed description of the contemporary state of stress in this fold‐and‐thrust belt and the adjacent foreland. The data now allow the recognition of five stress provinces, within which two general and different orientations of maximum horizontal stress SH can be distinguished: the Central and the Southwest Provinces, with a NNW–SSE to NNE–SSW orientation, and the East, Northwest and Southeast Provinces, orientated E–W to NW–SE. Each province has its own characteristic orientation. Measurements in three study areas are presented for comparison with already published acoustic anisotropy measurements, borehole breakout data, overcoring tests and triangulation measurements. The results show a generally good agreement with the new borehole slotter measurements. The tectonic implications of these stress data are discussed in terms of a large‐scale stress reorientation of the NW–SE orientated contemporary Central European stress field in the foreland of the western Alpine arc.

Latest Pliocene to recent thick-skinned tectonics at the Upper Rhine Graben – Jura Mountains junction

“…6a). This is in agreement with present-day SHmax-orientations inferred from in-situ stress measurements in the sedimentary cover (Baumann 1981;Müller et al 1987;Becker 1999Becker , 2000Reinecker et al 2003; Fig. 2).…”

“…2 and 3; see also Becker 1999Becker , 2000. This spread in orientations within the cover rocks coincides with that of the shortening directions obtained from paleostress analysis (Fig.…”

“…The extension axes show a very stable NE-SW-orientation throughout. However, the SHmax-orientations in the sedimentary cover, which is decoupled from the basement (comprising the crystalline basement, Permo-Carboniferous and Lower Triassic) along rheologically weak Middle and Upper Triassic evaporite layers, scatter from NNW over N to NNE, as is primarily deduced from in-situ stress measurements (Baumann 1981;Müller et al 1987;Becker 1999Becker , 2000Reinecker et al 2003; Fig. 2).…”

Seismic source characterization of the Alpine foreland in the context of a probabilistic seismic hazard analysis by PEGASOS Expert Group 1 (EG1a)

“…4); a few mechanisms are of thrust type. Strike slip mechanisms are in agreement with the left and right lateral strike slip faults in the Valais region (Pavoni 1980a) and with the in situ stress measurements at the southern end of the Rhine Graben near Basel (Becker 1999(Becker , 2000. In general, the NW-SE oriented maximum compressive stress is in agreement with the in situ measurements and corresponds with the orientation of the maximum horizontal crustal shortening; hence, it can be considered as constant over the last 10 million years (Pavoni 1980b).…”

Active Structures in Central Upper Rhine Graben, SW Germany: New Data from Landau Area using Electromagnetic Radiation (EMR) Technique and Cerescope

“…This deviation was explained as stress rotation between depth (where σH was determined with focal plane solutions) and the surface (where EMR measurements were carried out). At greater depth, within the basement of both URG and Jura Mountains, the direction of present-day maximum horizontal stress is consistently oriented NW-SE [49,67], while the recent stress field in the sedimentary cover (Mesozoic to Tertiary) as estimated from in-situ stress measurements, reveals NNW, N to NNE oriented maximum horizontal stresses [68,69]. Anticlockwise rotation of the maximum horizontal stress from the sedimentary cover to basement [27] indicates ongoing mechanical decoupling of the sedimentary cover from its basement along Early Mesozoic weak layers [70,71].…”