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在对东太平洋洋隆北纬8°—18°之间部分进行海束测深详查(detailed seabeaminvestigation)时,发现了一种与快速扩张中心伴生的新型火山-构造形态(图1和图2)。在洋隆轴部几处,这种新火山带不相连续,並在横向错开了一小段距离(1—15公里)。但与典型的洋脊-转换断层-洋脊板块边界不同的是,这些横向错开的洋脊终段以大致等于或大于横向错移距的距离相互重复。重复的两段洋脊明显地相向弯曲並沿走向相互归并。分隔重复扩张中心的是与它们的走向大致平行的一深达数百米的封闭形凹陷。重复扩张中心之间的地区是一兼具剪切和旋转变形而无明显转换平行构造的复杂地带。作者根据对扩张中心的蜡模研究认为,转换断层未能在横向错开很小的(<15公里)快速扩张中心处发育,是因为这里的岩石圈太薄太弱,不能维持典型刚性板块的扩张中心—转换断层型式。重复扩张中心的形态很不稳定,而且演变很快。演变的结果是两个重复扩张中心中的一个居于优势,另一个则被废弃。在高扩张速率下形成的一种有特殊意义的海底区,可能带有新近观察到的这种过程的烙印。
A detailed volcanic-tectonism (Fig. 1 and Fig. 2) associated with a rapidly expanding center was found during a detailed seabeaminvestigation of a portion of the eastern Pacific ocean between 8 ° -18 ° N. At several locations along the oceanic axis, the new volcanic belt is not continuous and is laterally offset by a short distance (1-15 km). However, unlike the typical ridge-transition fault-ridge segment boundary, these laterally offset ocean ridge segments repeat with each other at a distance approximately equal to or greater than the lateral offset. The two overlapping ridges apparently bend toward each other and merge with each other along the way. Separated from the center of repetitive expansion are generally parallel to their direction a deep depression of hundreds of meters. The area between repetitive expansion centers is a complex zone that combines shear and rotational deformation without obvious parallel transformation. According to the wax pattern study of the expansion center, the authors believe that the conversion fault failed to develop at a small (<15 km) rapid expansion center laterally misaligned because the lithosphere here is too thin to sustain the expansion of a typical rigid plate Center - transform fault type. The pattern of repeated expansion centers is unstable and evolves rapidly. As a result of the evolution, one of the two duplicate expansion centers dominates and the other discards. A special submarine zone formed at a high rate of expansion may carry the newly observed imprint of such a process.