2:30 PM - 2:45 PM
[SGL35-04] An investigation of coseismic OSL / TL time zeroing of quartz gouge based on high-velocity friction experiments
Keywords:Asano fault, luminescence, high-velocity friction experiment, time-zeroing
In the friction experiments, we used quartz grains of <150 μm separated from Tsushigawa granite (taken from the east wall of the Nojima fault Ogura trench site) as an analogue gouge. We conducted two series of experiments; (1) various slip rate experiments to see dependence of OSL/TL signal resetting on slip rate, (2) various displacement experiments to see dependence of OSL/TL signal resetting on displacement. In order to consider the effect of crushing, we separated the recovered sample into two grain sizes of <75 μm and 75-150 μm.
Our results of the OSL measurements are (1) <75 μm fraction of sheared gouge have high fast component ratio than the pre-sheared grains, (2) the fast component ratio of <75 μm fraction increases with increasing slip rate from 200 μm/s to 0.13 m, (3) OSL signal becomes to zero (time zeroing) in the experiment sheared under 0.65 m/s. The increase of the fast component ratio found in relatively low slip-rate experiments may be caused by the addition of the ionized electrons, that emitted from newly formed fracture surface during comminution, in electron center. The time zeroing observed in high-velocity friction experiment is attributable to rapid frictional heating up to 600 ℃ by temperature measurement. Based on the calculation of frictional energy we added to the experiment sheared under 0.65 m/s, we estimated the zeroing depth in natural conditions of earthquake (1.6 m in displacement) to 117 m.