We predict the shape of the outer rise along the Peruvian Trench (6°-21°S) using flexural and gravity modelling in order to study the elastic properties of the subducting/oceanic Nazca Plate (NP). We include in our modelling the hotspot swell topography of the Nazca Ridge (NR) in the ridge-trench collision zone (~15°S). Results show an anomalous overthickening of the oceanic crust beneath the NR (from ~6 to 20 km), which is capable to produce most of the swell topography (500–700 km wide and up to 2.2 km high). The swell was formed likely under isostatic conditions (T_e ~ 0 km) by the interaction of the NP with a hotspot-spreading center system. Despite the high buoyancy forces of the NR (0.5–4.0 × 10¹³ N/m) associated to the anomalous thick crust, the 45–50 Ma oceanic NP approaching the Peruvian Trench presents a well pronounced fore-bulge morphology with similar elastic thicknesses (T_e = 35 ± 5 km) to those found for cold and old oceanic plate in the western Pacific. Consistently, our results do not show evidence for plate weakening (reduced T_e values) in the NR-trench collision zone. We obtain similar results (T_e = 40 ± 10 km) north of the NR implying that the oceanic NP is strong prior to subduction along most of the Peruvian convergent margin. This is consistent with the lack of great outer rise events (M_w ≥ 6) and the absence of reduced uppermost mantle velocities offshore Peru suggesting the presence of a poorly hydrated and rigid lithospheric mantle.

为了研究俯冲/海洋纳斯卡板块（NP）的弹性特性，我们使用挠曲和重力模型预测了秘鲁海沟（6°-21°S）外部上升的形状。在我们的建模中，我们将脊-沟碰撞区（〜15°S）中的纳斯卡脊（NR）的热点膨胀地形包括在内。结果表明，NR下方的洋壳异常增厚（约6至20 km），能够产生大部分的隆升地形（宽500-700 km，高2.2 km）。膨胀可能是在等静压条件下（T _e〜0  km）通过NP与热点扩展中心系统的相互作用而形成的。尽管NR的浮力很高（0.5–4.0×10 ¹³N / m）与异常厚壳相关，接近秘鲁海沟的45-50 Ma海洋NP表现出明显的前凸形态，其弹性厚度（T _e  = 35±5 km）与寒冷和古老的相似西太平洋的大洋板块。一致地，我们的结果并未显示出在NR沟槽碰撞区中板弱化（T _e值降低）的证据。我们 在自然保护区以北获得了类似的结果（T _e = 40±10 km），这意味着在沿秘鲁大部分会聚边缘俯冲之前，海洋NP很强。这与缺乏重大的外部上升事件（M _w ≥6）且秘鲁近海的最高地幔速度没有降低，表明存在水合度低且刚性的岩石圈地幔。