We investigate the variations in the state of isostatic compensation of the Mariana subduction system. We first calculate and analyse the gravity-derived crustal thickness and non-isostatic topography of this region. The Mariana back-arc spreading centre and West Mariana Ridge are both close to Airy isostatic compensation. In contrast, the Mariana Trench axis is associated with a clearly defined zone of negative non-isostatic topography and free-air gravity anomaly (FAA), which have been shown to be caused by the flexural bending of the subducting Pacific Plate. The new analyses reveal that the southern Mariana Arc at 12.5°–16.7°N is associated with positive non-isostatic topography and a local zone of positive FAA, which we interpret to be the result of accretion of young volcanism on a relatively strong lithospheric plate and/or supported by the tectonic stresses induced by the interaction of the subducting Pacific Plate with the upper Mariana micro-plate.

中文翻译：

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马里亚纳俯冲系统的岩浆作用变化与构造补偿状态

我们研究了马里亚纳俯冲系统的均衡补偿状态的变化。我们首先计算和分析了该地区重力衍生的地壳厚度和非等静地形。马里亚纳弧后扩张中心和西马里亚纳海岭均接近艾里等静压补偿。相比之下，马里亚纳海沟轴与一个明确定义的负非等静压地形和自由空气重力异常（FAA）区域相关，这已被证明是由俯冲太平洋板块的弯曲弯曲引起的。新的分析表明，位于 12.5°–16.7°N 的南马里亚纳弧与正非等静压地形和局部正 FAA 区有关，