Gianni Guido M, Gallo Leandro C, Likerman Jeremías, Echaurren Andrés, Gianni Conrado R, Faccenna Claudio
German Research Centre for Geosciences (GFZ), Potsdam 14473, Germany.
Centre for Planetary Habitability, University of Oslo, Oslo 0316, Norway.
Sci Adv. 2025 Jul 11;11(28):eadv8872. doi: 10.1126/sciadv.adv8872.
Flat subduction, an intermittent phenomenon along active margins, arises from well-known causes, yet the mechanisms driving its expansion remain poorly understood. The prevailing view suggests that trenchward continental motion drives slab overthrusting, causing the flat slab to expand oceanward. Here, we explore an alternative mechanism: underthrusting of the subducting plate through forward propagation of the flat-slab hinge. We directly evaluate both hypotheses through a kinematic analysis of trench and flat-slab motions using a global flat subduction database cast into multiple absolute plate motion models. Our results indicate that flat-slab expansion reflects distinct end-member processes, with forward propagation emerging as the dominant mode. We present a framework for flat-slab propagation that emphasizes the dynamic interaction between lower-plate motion and slab pull from adjacent subduction zones, an interplay validated through numerical modeling. These findings challenge conventional assumptions and underscore the need to reconsider the role of lower-plate kinematics in flat-slab dynamics.
平板俯冲是一种沿活动边缘间歇性出现的现象，其产生原因众所周知，但驱动其扩展的机制仍知之甚少。普遍观点认为，向海沟方向的大陆运动驱动板块逆冲，导致平板向海扩张。在此，我们探讨一种替代机制：通过平板铰链的向前传播，俯冲板块的下插作用。我们使用纳入多个绝对板块运动模型的全球平板俯冲数据库，通过对海沟和平板运动的运动学分析，直接评估这两种假说。我们的结果表明，平板扩张反映了不同的端元过程，向前传播成为主导模式。我们提出了一个平板传播的框架，强调下板块运动与相邻俯冲带板块拉力之间的动态相互作用，这种相互作用通过数值模拟得到了验证。这些发现挑战了传统假设，并强调有必要重新考虑下板块运动学在平板动力学中的作用。
