Thermal structure, coupling and metamorphism in the Mexican subduction zone beneath Guerrero
Thermal structure, coupling and metamorphism in the Mexican subduction zone beneath Guerrero
复制标题
格雷罗州下方墨西哥俯冲带的热结构、耦合和变质作用
DOI：
10.1111/j.1365-246x.2004.02325.x
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发表时间：
2004
影响因子：
2.8
通讯作者：
G. Sewell
中科院分区：
文献类型：
--
作者：
V. Manea;M. Manea;V. Kostoglodov;C. Currie;G. Sewell
温度是控制俯冲板间断裂发震耦合段、过渡段和部分耦合段的范围和位置的重要因素之一。从稳定震间期的连续GPS观测推断出的耦合断层宽度和2001 - 2002年发生在Guerrero俯冲带的最后一次缓慢地震滑动事件（M w ~ 7.5）的瞬变宽度从海沟延伸至180 - 220公里。以前的热模型没有考虑到格雷罗俯冲带的这种极宽耦合界面，其特征是浅亚水平板块接触。在本研究中，采用有限元模型考察了温度对耦合区域宽度的约束。数值格式求解了一个由二维Stokes方程和二维稳态传热方程组成的系统。耦合区的上倾角限制在100到150°C之间，而下倾角限制在450°C作为从部分耦合到稳定滑动的过渡。从整个耦合带来看，孕震带仅从海沟延伸至约82公里（从大型俯冲逆冲地震的破裂宽度推断），对应于250°C等温线。在距离海沟180 - 205公里处，450°C等温线与俯冲板块表面的交叉点只需要少量的摩擦加热。利用计算得到的俯冲板块内的地温和MORB相图估计了大洋俯冲地壳内的变质层序。变质层序与沿板间断裂的耦合变化具有一定的相关性。
SUMMARY Temperature is one of the most important factors that controls the extent and location of the seismogenic coupled and transition, partially coupled segments of the subduction interplate fault. The width of the coupled fault inferred from the continuous GPS observations for the steady interseismic period and the transient width of the last slow aseismic slip event (M w ∼ 7.5) that occurred in the Guerrero subduction zone in 2001‐2002 extends up to 180‐220 km from the trench. Previous thermal models do not consider this extremely wide coupled interface in Guerrero subduction zone that is characterized by shallow subhorizontal plate contact. In this study, a finite element model is applied to examine the temperature constraints on the width of the coupled area. The numerical scheme solves a system of 2-D Stokes equation and 2-D steady-state heat transfer equations. The updip limit of the coupling zone is taken between 100 and 150 ◦ C, while the downdip limit is accepted at 450 ◦ C as the transition from partial coupling to stable sliding. From the entire coupled zone, the seismogenic zone extends only up to ∼82 km from the trench (inferred from the rupture width of large subduction thrust earthquakes), corresponding to the 250 ◦ C isotherm. Only a small amount of frictional heating is needed to fit the intersection of the 450 ◦ C isotherm and the subducting plate surface at 180‐205 km from the trench. The calculated geotherms in the subducting slab and the phase diagram for MORB are used to estimate the metamorphic sequences within the oceanic subducting crust. A certain correlation exists between the metamorphic sequences and the variation of the coupling along the interplate fault.