The Ordos block is peripherally surrounded by fault zones and faulted basin zones of Cenozoic age.Its southwestern boundary is a compressional tectonic belt trending NW, along which left-lateral strike-slip fault zones with thrust components, such as the HaiyuanLiupanshan fault zone, and corresponding faulted basins have developed, with both the maximum left-lateral strike-slip rate and the maximum horizontal shortening rate of 10mm/a. Both the Yinchun-Jilantai faulted basin zone of its western boundary and the Shanxi faulted basin zone of its eastern boundary are NNE-trending right-lateral shear zones with extension components, while both the Weihe faulted basin zone of its southern boundary and the Hetao faulted basin zone of its northern boundary are nearly EW-trending left-lateral shear zones with extensional components.All these shear zones have Holocene horizontal and vertical slip rates of 5mm/a and 0.3~3mm/a, respectively.With regard to the history of their development these faulted basin zones have a different timing of initiation.The Weihe and Yinchuan faulted basin zones have at first initiated in Eocene, the Hetao faulted basin zones in Oligocene, and the Shanxi faulted basin zones in Pliocene.During the Cenozoic, the Ordos block has been a situation of slow uplift, with an amount of uplift of 160m since 1.4Ma B.P. For the Ordos internor, the Moho discontinuity is 40~42km in depth, with a gentle variance, and the high conductive layer of the upper mantle is 123~131km in depth, while for the peripheral faulted basin zones of the block, the Moho discontinuity has relatively uplifted about 1.5~6km, and the high conductive layer of the upper mantle is only 70~100km in depth.Deformation analysis from geodetic surveying indicates that the Ordos block and its southwestern boundary area now are still uplifting, with uplift rates of 1~2.8mm/a and 4.4mm/a, respectively, and that the peripheral faulted basin zones are relatively subsiding, with an amount of -4~-5mm/a.Within the internor of the Ordos block, there are a few earthquakes of magnitude 4~5, and no earthquakes magnitude equal to and more than 6. All the earthquakes whose magnitudes are equal to and more than 6 in this area have occurred along peripheral active fault zones and in faulted basin zones.The results of the solutions of mechanism at the sources and the measurments of ground stress and the fault-slip vector indicate that the principle compressional stress in the Ordos area is oriented in NE-NEE, consisting with the regional stress field showed by the kinematic characterics of the peripharal active fault zones of the Ordos block.Such a stress regime may probably come from the Qingzang Block movement which is towards the northeast.On the other hand, the upwelling of deep materials beneath the faulted basins could play an important role in the neotectonic movement of the Ordos block.So the combination of the regional stress field with the upwelling of deep materials controls the dynamics of the Cenozoic Ordos block movements.
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