We invented a completely new simple method and new equipment necessary for high-resolution active fault studies. Vertical thin sections of unconsolidated soil layers are extracted by a newly invented sampler named “Geo-slicer”.
Extracted sections can be taken to a laboratory for close examination or can be displayed at a meeting or even stored for future re-examinations (Fig. 1). This method enables us to carry on high-resolution analyses not only in active fault studies but also in other fields of Quaternary sciences with less expenditure of time, labor and money.
We made three different-sized Geo-slicers and tested them successfully in the field. A Geo-slicer is made of steel and has a simple structure composed of a box and its shutter (Figs. 2 and 3). Several devices are implemented to the box and the shutter, such as wedge-shaped side walls and a stopper at the bottom of the box for easy pull-out of the equipment and steady-holding of samples (Fig. 4).
For sampling, we firstly intrude the box vertically down into the ground by using a vibro-hammer (Photo 1) and then shutter sliding along the thin slits attached to the both sides of the box, and pull out the equipment containing samples.
The extracted layers of sediments are surprisingly undisturbed and show almost the same features as previously observed on trench walls excavated close to the extraction sites (Photos 2 and 3). The largest sample collected by this method is 150 cm wide, 270 cm long (deep) and 8-15 cm thick (Photo 4).
This sampling method is far more effective on active fault studies than the conventional trench excavation technique and we will be able to carry out three-dimensional analysis of active faulting, restoration of horizontal fault slips and so on for paleoseismological studies (Fig. 6).