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早期伸展期间,冷的大陆岩石层变薄并发生沉降,形成裂谷盆地。如果继续拉伸并最终导致破裂,裂开的、大大减薄的板块便沉降至海平面以下深处,形成一对共轭的裂离边缘。尽管盆地和边缘是普遍存在的结构,但是从中等程度伸展的盆地到明显拉伸边缘的变形过程还不清楚,就像目前研究一致报道的那样,地壳减薄比由脆性断层作用引起的伸展要强烈1-4。该伸展差异可能起因于脆性地壳层和塑性地壳层的差异拉伸2,但是这不足以解释共轭边缘的典型非对称结构5,6——在剖面上,一侧边缘显示逐渐变薄,伴随着大断裂发育,而共轭的另一侧显示突然变薄,却伴随着小断裂发育5。裂陷早期开始活动的全地壳拆离,在理论上可以引起减薄和非对称1,但在机制上是有疑问的。此外,伸展差异在共轭边缘的两侧均有发生,导致外部形态的矛盾——两侧边缘均像拆离断层的上盘7,8。不同的模型认为,由于地震成像的限制,许多脆性伸展未被探测到,其原因或是地震分辨率难以识别的断裂9、基底顶部100km级别拆离面上不可见的变形8,或者是剖面上断裂组合的构造复杂性3。这里我们利用深度偏移地震成像准确地测量断层伸展,并将其与地壳减薄进行比较。利用观测资料建立了一种裂陷期运动学平衡模型,通过由裂陷盆地到非对称结构过程中断层控制的地壳减薄,和共轭裂离边缘的超级减薄解决了伸展差异。与现有的认识相比,观测资料支持这种观点:在地震资料上地壳减薄首先可由清晰可见的简单安德森断裂解释。
During the early extension, cold continental rock layers became thin and settled, forming rift basins. If it continues to stretch and eventually rupture, the cracked, greatly thinned plate settles to a depth below sea level, forming a pair of conjugate cleaved edges. Although basins and margins are ubiquitous structures, the process of deformation from moderately extended basins to markedly stretched edges remains unclear. As currently reported, crustal thinning is greater than stretching due to brittle faults Strongly 1-4. This difference in stretch may result from differential stretching 2 of the brittle crust and the plastic crust, but this is not sufficient to account for the typical asymmetric structure 5, 6 of the conjugate edge - on the profile, the side edges show a gradual thinning with Large rupture develops, while the other side of the conjugate shows sudden thinning, but with small rupture. All-crustal detachment started early in the rifting, theoretically causing thinning and asymmetry1, but there are questions about the mechanism. In addition, the stretching difference occurs on both sides of the conjugate edge, resulting in the contradiction of the external shape - both edges are like the detached upper plate 7,8. Different models suggest that many brittle extensions are undetected due to seismic imaging limitations due to fractures that are difficult to discern with seismic resolution 9, invisible deformations at the level of 100 km at the top of the basement 8, or in profile Structural complexity of the fracture combination 3. Here we use depth-offset seismic imaging to accurately measure the extent of faults and compare them with crustal thinning. Based on the observed data, a kinematic equilibrium model of the rifting period was established. The difference in extension was solved by the crustal thinning controlled by the faults in the process of the rift basin to the asymmetric structure and the super thinning of the conjugate rift edge. Observational data support the notion that the crustal thinning of seismic data is first explained by the clearly visible simple Anderson fault.