The Fen-Wei rift system, 1200 km long and 10–100 km wide, is situated in the northern part of East China, following a zigzag path trending NNE-SSW. It cuts the Shanxi-Shaanxi Plateau (average altitude 2 km) reaching depths of 5–6 km, and is filled with Cenozoic sediments (thickness 3–4 km). Accompanying the mainly vertical displacement of the marginal fault zones, the rift system extends laterally up to 7 km (greatest in the southern part). Earthquakes with foci 10–30 km deep are frequent; M = 8. Eruptions mainly of alkaline basalts took place 24 times in the Cenozoic. Heat flow appears to be rather high as marked by 17 hot springs. Negative Bouguer anomalies are dominant, reaching a maximum of −200 mGal. The crust is 38 km thick on average, 2–4 km thinner than that of the marginal uplift zones. Possibly a mantle arched belt exists below. In the upper mantle, V p = 7.95 km/ s. Originally the rift system was part of the broad ancient China platform. In the Early Jurassic, the latter underwent activation and became the North China diwa (geodepression) region ∗ ∗ The term “diwa” is derived from Chinese words meaning geodepression, being a special kind of intermountain-structural basins occurring mostly on the ancient platform region, filled chiefly with mollasoid sediments. A diwa region is marked with high relief and by basins, diwa as negative units intercalated with ranges as positive units called “geodomes”. It is a post-platform mobile region, the third geotectonic element of the continental crust besides géosynclinal and platform regions, proposed by the author in 1959 (Chen, 1959, 1960b, 1965, 1980, etc). Its synonym is “activated region” proposed by the author in 1956, because it is formed by the activation of the platform (Chen 1956, 1960a). . In the Cenozoic, the Fen-Wei rift system formed as a result of contraction of the crust in this region combined with creeping of asthenospheric material. It may be referred to the crevice type of post-platform continental rift zones in E.E. Milanovsky's classification.