[en] A structural analysis is presented of mare ridges in an area of about 360 000 km² in the southeastern part of Oceanus Procellarum just north of Mare Humorum. Mare ridges can be regarded as the result of large-scale natural tectonic deformation experiments coupled with and extended by volcanic phenomena. The old lunar crust has evidently retained part of the Moon's original tectonic elements throughout major exo- and endogenic events. Those structures which in places were flooded by mare lavas were also the first flaws to yield and to extend during younger tectonic and volcanic activity. Linear mare ridges may thus have formed at the activated and re-activated junctures of lunar crustal plates. Implications for the tectonics of mare ridges evidently show that one global stress field cannot account for all lunar tectonics but that global and areal variations in the lunar stress system have probably occurred. (Auth.)