The general trend of the Büyük Menderes Graben is E–W but it extends NE–SW near the Aegean Sea (Fig. 1b). The Argavlı site is located near the northeastern end of the NE–SW trending part of the graben (Fig. 2a). The active fault was mapped using geological and geomorphological indicators but its precise location in the study site was not clear because the field has been used for agriculture, which erases surface evidence of faulting. GPR surveys were applied to locate the fault precisely. The first measurements were taken with the 250 MHz antenna along an 80-m profile to obtain a general view of the subsurface (Fig. 2b). After the processing this long profile, we re-marked some offset reflectors and hyperbolas between 10 and 25 m along the profile (Fig. 3). This part of the long profile was scanned again with the 250 MHz antenna with a shorter trace interval (∼5 cm) to achieve higher lateral resolution (Fig. 2b). Thereafter, we used the 500 MHz antenna for a more detailed analysis of the offset (higher vertical resolution) and for identifying different sedimentary units