By developing the method of Acerbi et al, the authors obtain local regularity in Orlicz spaces for the linear second-order parabolic equations with small BMO coefficients in nondivergence form. Such regularity estimates can be applied to the study of the existence of solutions in W^2,1_p.

In the lake-face strata located in the lower reach of the Qingshuihe River, Ningxia with the latitude of 37.4° N and the elevation about 1230m, involution dated in late period of late Quaternary was discovered, which indicates that the south limit of permafrost had once expanded approximately to the latitude of 37.4° N in that time in Ningxia and that the annual mean temperature was 8～9℃ lower than today. Because the intensive tectonic uplift in the northeast margin of Tibetan Plateau and cold and dry weather in the last glacial maximum, the Qingshuihe River was so blocked that along the margin of the blocked-lake the involution was developed.

Enkai fault zone is one of the important fault zones along the coast area of southeast China. The fault zone with the length of about 160km is mainly constituted by three approximately parallel NE faults (F₁ and F₂ incline to NW and F₃ incline to SE). In Tertiary the faults moved in a way of normal faulting. However, at the end of Tertiary or early Quaternary, the faults turned to be compressive ones by WNW-ESE strong horizontal force, resulting in compressive deformation along the whole fault zone. Probably because of weakening of the WNW-ESE compressive stress from middle Pleistocene and because of weakening tendency of compressive stress from the south to the north along the southeastern coast of China, compressive stress in the south segments of the fault zone is strong enough to make the faults move in a way of reverse faulting and form reverse faulting landform while compressive stress in the north segments of the fault zone is so weak compared to isostacy force as to make the fault blocks restart isostacy uplift, move in a way of normal faulting and form normal faulting landform. Because of the approximate equilibrium between isostacy and horizontal compressive force in the middle segments of the fault zone, the faults have kept relatively steady state, resulting in weak contrast landform. In about late Pleistocene, a series of NW faults in the fault zone came into being or reactivated. On one hand, these NW faults, due to small angle between their strike and main compressing stress axis, have relatively small friction stress on the fault surfaces so that they could be moved more easily and often offset NE faults, forming obstacles to the strike slip of NE faults. On the other hand, the movements of NW faults release some strain energy so that they weaken compressive stress on the NE fault surfaces. Both of them reduce the activity of NE faults.