2.4. Complementary field investigations

A second phase of this study concerned the verification of morphological evidences seen on map interpretations. Several field investigations were done during summer to winter 1997. The exploration concentrated on first level target (2.2) and also, any visible outcrop of quaternary formation exposed in quarries. Some known quaternary faulting evidence was also visited and more accurate research carried out (Riedseltz, Saverne, Achenheim). Some new sites showing the presence of liquefaction patterns were also discovered.

An important conclusion of this second phase of the study, is that numerous liquefaction/faulting evidences were observed in the northern part of the URG. No liquefaction evidences and only rare fracturing evidences were observed in the southern part (South Mulhouse).

Verification of morphological scarps in the field allowed us to select some sites for further investigations (geophysics, levelling). Theses sites present rarely exposed quaternary formations because of the important anthropism occupation (fields, villages) or vegetation cover (woods). The only way to discriminate whether or not scarps result from tectonics is to investigate with geophysical methods or trenching.