Shallow slip on the plate‐boundary fault during the 2004 Mw 9.2 Aceh‐Andaman Earthquake, offshore North Sumatra, has been linked to thick incoming sediments on the oceanic plate with advanced diagenetic and sediment property changes at the depths of plate boundary fault development. We couple age control, physical, and thermal property measurements from International Ocean Discovery Program (IODP) drilling with multichannel seismic reflection data to reconstruct the thermal structure and evolution of the incoming sediment column, up to the point of accretion/subduction. Lithospheric thermal rejuvenation around 58 Ma is required to explain anomalously high heat flux at IODP Site U1480, and heat flux within the trench is suppressed by very high sediment accumulation rates during the development of a thick trench wedge. Accumulation of up to ∼4.5 km of thick Nicobar Fan and trench wedge sediments produces temperatures >150°C within the basal sediments where the décollement develops, resulting in total pre‐subduction diagenetic dehydration of basal sediments. The smectite‐illite transformation within these basal sediments produces sufficient fluid to explain a polarity reversal on a pre‐décollement reflector. We suggest that the boundary between basal‐pelagic and siliciclastic‐fan sediments has trapped fluid over the last ∼1 Myr, as a result of primary lithological properties, diagenetic fluid release, and cementation, controlling décollement formation at this weakened level. Pre‐subduction dehydration of large portions of the accreted sediment column strengthens the décollement beneath the prism, extending co‐seismic velocity‐weakening behavior close to the trench, which may occur at other subduction zones with similar sediment compositions, thicknesses, and/or temperatures.

中文翻译：

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进入北苏门答腊俯冲带的沉积物的热和脱水状态的演变

在北苏门答腊岛2004年Mw 9.2亚齐-安达曼地震中，板块边界断层的浅层滑移与大洋板块上较厚的进入沉积物有关，在板块边界断层发展的深处，成岩作用和沉积物特性发生了提前变化。我们将国际海洋探索计划（IODP）钻井的年龄控制，物理和热属性测量与多通道地震反射数据结合起来，以重建热结构和进入沉积物柱的演化，直至吸积/俯冲。IODP站点U1480异常高的热通量需要大约58 Ma的岩石圈热复兴，并且在厚沟槽楔的发展过程中，非常高的沉积物堆积速率抑制了沟槽内的热通量。最多可累积约4个。5 km厚的尼科巴扇形和沟槽楔形沉积物在底泥沉积发育的基底沉积物中产生高于150°C的温度，从而导致基底沉积物的全部俯冲前成岩作用脱水。这些基础沉积物中的蒙脱石-伊利石转变产生了足够的流体，以解释前斜反射器上的极性反转。我们认为，由于主要的岩性，成岩性流体释放和胶结作用，基底-上层沉积和硅质-扇形沉积物之间的边界将流体滞留在最后一个〜1 Myr上，从而在这种弱化水平上控制了扇状沉积的形成。大部分积积沉积物柱的俯冲前脱水作用增强了棱柱下方的剥脱作用，使同震速度减弱作用扩展到了靠近沟槽的位置，