The amplitude of variations in axial depth and across-axis relief that define spreading center segmentation vary systematically with spreading rate. Seismic and gravity data show that crustal thickness also varies along segments. We derive a highly idealized model to relate axial lithospheric thickness, crustal thickness, and effective magma source region size to segment-scale variation in axial depth and across-axis relief. All magma to build the crust is assumed to pool in a segment-centered magma source region and is distributed along the spreading axis by flow in dikes. The magma source and dike are regarded as a closed system and the magma pressure is taken to decrease linearly with the volume of magma going into dikes. The pressure-volume relation driving lateral magma flow is taken to be proportional to the along-axis gradient of depth. Axial depth variations depend on: (1) local isostatic compensation from crustal thickness variations; and (2) across-axis relief or axial valley depth. The axial valley depth is related to crustal and lithospheric thickness using the recently published model of Liu and Buck (2018). Excellent fits to bathymetric data for 12 segments from intermediate to ultra-slow spreading ridges are found by varying three model parameters ($H_{C0}$, $H_L$ and ΔP/ΔV). The dependence of pressure drop on volume withdrawn is parameterized in terms of an effective radius for a spherical source region in an elastic half-space. A key result is that the effective magma source radius increases with spreading rate.

定义铺展中心分割的轴向深度和横轴起伏的变化幅度随铺展速率系统地变化。地震和重力数据表明，地壳厚度也随着分段而变化。我们推导出了一个高度理想化的模型，将轴向岩石圈厚度、地壳厚度和有效岩浆源区大小与轴向深度和横轴起伏的分段尺度变化联系起来。假设所有形成地壳的岩浆都聚集在以段为中心的岩浆源区，并通过岩脉流动沿扩展轴分布。岩浆源和岩脉被视为一个封闭系统，岩浆压力随着进入岩脉的岩浆量呈线性下降。驱动横向岩浆流的压力-体积关系被认为与深度的沿轴梯度成正比。轴向深度变化取决于：（1）地壳厚度变化的局部均衡补偿；(2) 横轴起伏或轴向谷深。使用 Liu 和 Buck (2018) 最近发表的模型，轴向谷深与地壳和岩石圈厚度有关。通过改变三个模型参数（$H_{C0}$, $H_{升}$和 Δ P /Δ V）。压降对提取体积的依赖性根据弹性半空间中球形源区域的有效半径进行参数化。一个关键结果是有效的岩浆源半径随着扩散速度的增加而增加。