The segmentation of mid‐ocean ridges is a defining characteristic of seafloor spreading, yet some tectonic processes operating at segment boundaries remain poorly understood. Here, we analyze new satellite‐derived vertical gravity gradient (VGG) data, which reveal an abundance of off‐axis seafloor features that are oblique to ridges and transform faults and thus reflect the occurrence of ridge propagation at some segment boundaries. However, unlike many propagating ridges, these features commonly reverse direction leaving W‐shaped signatures in the seafloor which we refer to as “seesaw propagators” (SSPs). Using the VGG, we have documented these globally and find that: (1) SSPs are ubiquitous on seafloor that formed at half spreading rates between 10 and 40 mm year⁻¹ and their total length is about 1/3 that of fracture zones. (2) The lithospheric age offset across SSPs (0–2.5 Ma) is less than transform faults (2–10 Ma), which likely reflects a rheological threshold, whereby only young and weak lithosphere allows for “non‐rigid” SSP behavior. (3) Isostatic modeling of well‐surveyed SSPs confirms that they formed on young and thin (3 km) lithosphere. (4) The directional changes of SSPs in both time and space appear largely uncorrelated and cannot be explained by previous regional‐scale models invoked to explain unidirectional ridge propagation and thus require a different driving force.

中文翻译：

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海洋垂直重力梯度揭示了“跷跷板”山脊传播的全球分布及其构造意义

中海洋脊的分割是海床扩展的定义特征，但是在分割边界处进行的一些构造过程仍知之甚少。在这里，我们分析了新的卫星衍生的垂直重力梯度（VGG）数据，这些数据揭示了大量倾斜于海脊并变换断层的离轴海底特征，从而反映了在某些段边界发生海脊传播的情况。但是，与许多繁殖脊不同，这些特征通常是反向的，在海底留下W形特征，我们称其为“跷跷板繁殖器”（SSPs）。使用VGG，我们已经证明这些全球和发现：（1）SSP的是无处不在的海底形成半扩张速率10和40mm之间每年^-1它们的总长度约为断裂带的1/3。（2）跨SSP的岩石圈年龄偏移（0–2.5 Ma）小于转换断层（2–10 Ma），这很可能反映出流变学阈值，因此只有年轻而脆弱的岩石圈才允许“非刚性”的SSP行为。（3）进行了充分测量的SSP的等静压模型证实了它们是在年轻而薄的（3 km）岩石圈上形成的。（4）SSPs在时间和空间上的方向变化在很大程度上似乎是不相关的，并且不能被先前用来解释单向脊传播的区域尺度模型所解释，因此需要不同的驱动力。