Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

The NGF-1 trench: he G This trench located in a N-S striking fault- segment crossing perpendicular to the fault scarp and exposing the scarp-derived deposits. The trench is ca. 14 m long and ca. 6 m high (Fig. 3A). The main fault responsible for the east-facing scarp dips 80° to the east at the trench site. The trench exposes one colluvial wedge (CW1d and CW1w in Fig. 3B) overlying a strongly fractured gypsic soils developed in alluvial gravels. Based on the position of a gypsic soil (GS in Fig. 3B) on both sides of the fault, we determined a net normal offset of 3.8 ± 0.1 m. The NGF-2 trench: Trench NGF-2 is 8 m long and 1.65 m high (Figure 4), and it is excavated in the down- going fault block along a laterally displaced channel filled with aeolian and alluvial sandy deposits (AD1, AD2 and AD3 units, Fig. 4). The channel is incised in Plio-Pleistocene gravels (AGs in Fig. 4). Near the fault, the sedimentary infill of the channel is accommodated in a like- graben structure limited to the west by the main fault and to the east by a subvertical fault (Fig. 4). The main fault dips 70° to the east; it connects the sedimentary infill of the channel (AD1 and AD2 in Fig. 4) with the strongly cemented alluvial gravels (AGs) located to the west of the fault. Along dip-fault displacement is ca. 1.75 m. In the graben structure, there are several east-dipping deformation bands that displace AD1 and AD2. The deformation bands produce vertical separations of 25 and 10 cm in the AD1 and AD2 layers, respectively. AD1 is 28 cm thicker in the graben than outside the graben, and AD2 is 27 cm thicker in the graben. All the structures in the graben are sealed by AD3. Fig. 3: NGF-1 Trench. A) Geometry of the scarp; the slope angles of the scarp profile are given in degrees, black lines represent the surface offset of the topography, and blue lines represent the offset of the gypsic soil. B) Logging of the southern wall of trench NGF-1.