The forearc region remains key in understanding the dynamics of convergent plate tectonics. This study focuses on the mechanisms governing tectonic processes within the overriding plate forearc which spans from the trench to the volcanic arc at two key and relatively well studied regions: the Japan Trench and the Middle America Trench offshore SE Costa Rica. We address the questions that have arisen concerning material input into the plate boundary, whether by subduction, accretionary prism formation, or tectonic erosion. In the Japan Trench case study, while tectonic accretion occurs near the trench axis, significant forearc subsidence suggests net material removal, possibly through tectonic erosion that has transferred material to the subducting slab. Debate surrounds the mechanism driving forearc subsidence, with recent studies proposing extensional tectonism as a possible mechanism to exclude subduction erosion. However, seismic evidence challenges this hypothesis, as normal faults indicative of forearc extension are not prominent. Moreover, a quantitative mass-balance analysis fails for the forearc if extensional tectonics rather than tectonic erosion is assumed to have predominantly shaped the margin. The spatio-temporal progression of subsidence across the forearc is further explored; this indicates that peak subduction erosion has occurred beneath the lower slope. The Middle America Trench in SE Costa Rica has also been extensively studied with several drilling expeditions, with particular focus on the area where the aseismic Cocos Ridge is subducting beneath the Caribbean plate. Here the subduction of topographic relief has been traditionally viewed as a process that enhances subduction erosion. Recent studies have challenged this perspective, suggesting instead that subducting topography might lead to net accretion to the margin through various mechanisms. Ocean drilling expeditions provide valuable data on sedimentary successions and forearc tectonic evolution. These drilling data have been not always used to the best of their capacity, which has led to significant discrepancies between drilling-based inferences and seismic interpretations, in particular regarding the presence and nature of unconformities within the forearc sediments. Borehole observations strongly favor the inference that inboard the Cocos Ridge a large amount of subsidence has occurred, linked to recent subduction erosion beneath this forearc.

中文翻译：

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深入了解弧前构造中构造伸展和压缩与俯冲侵蚀的作用：以日本海沟和中美洲海沟为例


弧前区域仍然是理解会聚板块构造动力学的关键。这项研究的重点是控制上覆板块前弧内的构造过程的机制，该弧跨越两个关键且研究相对充分的区域的海沟和火山弧：日本海沟和哥斯达黎加东南部近海的中美洲海沟。我们解决了有关物质输入板块边界的问题，无论是通过俯冲、增生棱柱形成还是构造侵蚀。在日本海沟案例研究中，虽然构造增生发生在海沟轴附近，但弧前的显着沉降表明物质的净去除，可能是通过构造侵蚀将物质转移到俯冲板片而实现的。争论围绕着弧前沉降的驱动机制，最近的研究提出伸展构造作用是排除俯冲侵蚀的可能机制。然而，地震证据对这一假设提出了挑战，因为表明弧前延伸的正断层并不明显。此外，如果假设伸展构造而不是构造侵蚀主要塑造了边缘，则对弧前进行定量质量平衡分析就会失败。进一步探讨了弧前沉降的时空进展；这表明峰值俯冲侵蚀发生在较低斜坡下方。哥斯达黎加东南部的中美洲海沟也通过多次钻探考察得到了广泛研究，特别关注抗震科科斯海岭正在俯冲到加勒比板块之下的区域。在这里，地形起伏的俯冲传统上被视为增强俯冲侵蚀的过程。 最近的研究对这一观点提出了挑战，认为俯冲地形可能会通过各种机制导致边缘的净吸积。海洋钻探探险提供了有关沉积层序和弧前构造演化的宝贵数据。这些钻井数据并不总是得到充分利用，这导致基于钻井的推论和地震解释之间存在显着差异，特别是在弧前沉积物内不整合面的存在和性质方面。钻孔观察强烈支持这样的推论，即科科斯海岭内侧发生了大量沉降，这与弧前下方最近的俯冲侵蚀有关。