No abstract

No abstract

No abstract

Two groups of Quaternary faults occur in the southeastern Korean Peninsula. The first group is north‐northeast‐striking, high‐angle dextral strike–slip faults. The second group is north‐northeast‐striking, low‐angle reverse faults that represent the reactivation of the pre‐existing normal faults. Optically stimulated luminescence dating of Quaternary sediments cut by one of the reverse faults constrains the faulting age to post‐32 Ka. These faults seem to be capable of further slip under the current tectonic stress regime, as determined by recent earthquake events in northeast Asia. Therefore, the traditional concept that the southeastern Korean Peninsula is seismically stable should be reappraised.

No abstract

No abstract

In order to investigate the evolution of lattice preferred orientation (LPO) obtained during deformation, we carried out post-deformational annealing experiments for rock analog materials, octachloropropane (C 3 Cl 8 ) and norcamphor (C 7 H 10 O). Polycrystalline aggregates deformed at low-temperature/high-strain-rate conditions show complete obliteration of grain-boundary microstructures (e.g., grainshape foliation) during annealing, but maintain the LPO by rapidly growing small grains which have inherited crystallographic orientations from the adjacent old grains. On the other hand, polycrystalline aggregates deformed at high-temperature/low-strainrate conditions tend to maintain deformation microstructures during annealing, due mainly to the presence of subgrain boundaries which pin the motion of grain boundaries. The limited mobility of grain boundaries also allows preservation of the LPO obtained during deformation. During grain growth at the stage when textural equilibrium is reached, polycrystalline aggregates show no preferential removal of grains of certain crystallographic orientations. Therefore, our experimental results suggest that LPO obtained during deformation is insensitive to post-deformational annealing process. A microstructural analysis of naturally deformed-then-annealed quartzite indicates that the similar processes may operate in natural rocks.

No abstract