Bedding tilt test of paleo-stresses determined from mesoscale faults in a Quaternary fold belt, Central Japan
Abstract
We show that bedding tilt test is feasible to infer paleo-stresses from mesoscale faults in fold belts. The multi-inverse method was used to determine paleo-stresses. Significant stresses were recognized by the convergence of clusters, which designate possible states of stress, during progressive untilting of the fault-slip data just as that of paleomagnetic bedding tilt test. % We applied this technique to the mesoscale faults in a very young (late Pleistocene) kink fold with a sub-shorizontal hinge line in Niigata oil field, Japan. Fold wavelength is about 5--10 km around the study area. The progressive tilt correction indicates that strike-slip faulting regime of stress caused faulting in earlier folding phase. The σ_1- and σ_3-directions were determined perpendicular and parallel to the fold axis, respectively. This appears discordant to the fold structure that results in vertical elongation and horizontal shortening of the folded sedimentary sequence. % We suggest that flexural folding lessened regional compression within the flexed layers whence the fault-slip data were collected. The layers form a kink fold, which is thought to develop in strongly layered sequences that have a strong planar mechanical anisotropy. Anisotropy may have prevent us to detect overall stress field from mesoscale faults. The σ_3-direction is explained by the gravitational force along the increasingly plunging fold hinge.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....1821Y