Crustal structure of the central Sunda margin at the onset of oblique subduction
Crustal structure of the central Sunda margin at the onset of oblique subduction
复制标题
斜俯冲开始时巽他边缘中央的地壳结构
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
C. Reichert
中科院分区：
文献类型：
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作者：
H. Kopp;E. Flueh;D. Klaeschen;J. Bialas;C. Reichert
总结
1998年和1999年，印度尼西亚巽他弧中心的会聚边缘是反射和折射地震勘探的目标。沿着两条横跨苏门答腊南部和巽他海峡外俯冲复合体的地震测线，收集了重合的多通道和广角数据，并在苏门答腊外的弧前盆地内收集了两条折射走向线。所获得的数据的综合分析，使我们能够提出一个详细的模型，俯冲带的应变分区的开始发生由于斜俯冲的发病。俯冲板块的倾角沿两条倾角线沿着很好地确定，从苏门答腊岛外高压到巽他海峡的横向增加5°到7°得到了补充重力模型的支持。下行板块被追踪到超过30公里的深度。在两条反射倾斜线上，一个明显发育的后挡结构下的沟坡折定义了向陆地终止的活跃增生棱镜，并将其从外部高。活动俯冲吸积的支持下，横向增加的速度之间的变形前和活动的backstop结构。外高压的地震波速度在两条线上都是中等的沿着（在20公里深度处小于5.8 km s−1），这表明它是一种沉积物。沿着两条倾斜线的外部高点沿着追踪的崎岖的顶部基底下的反射率降低支持高度的变形和物质压实。在弧前区域已经积累了几公里的沉积物，尽管只有在苏门答腊南部海域才认识到一个独特的形态盆地，而在巽他海峡海域则没有形成。在巽他海峡南部遇到的爪哇大陆架的水深高程对应于那里基底高的速度增加，并与巽他海峡张扭盆地的伸展结构相连。在弧前域形态上观察到的差异也反映在下地壳结构上。关闭苏门答腊南部，速度-深度模型清楚地表明，大陆型地壳下的弧前盆地，而较低的速度被发现在巽他海峡弧前域。在苏门答腊岛外，从折射走向线中获得了对上板块结构的一些三维约束，这也得到了合成数据建模的支持。
Summary
The convergent margin of the central Sunda Arc in Indonesia was the target of a reflection and refraction seismic survey conducted in 1998 and 1999. Along two seismic lines across the subduction complex off southern Sumatra and off Sunda Strait, coincident multichannel and wide-angle data were collected, complemented by two refraction strike-lines in the forearc basin off Sumatra. The combined analysis of the acquired data allows us to present a detailed model of the subduction zone where initiation of strain partitioning occurs due to the onset of oblique subduction. The dip of the subducted plate is well defined along both dip-lines and a lateral increase from 5° to 7° from beneath the outer high off Sumatra to Sunda Strait is supported by complementary gravity modelling. The downgoing slab is traced to a depth of more than 30 km. On both reflection dip-lines, a clearly developed backstop structure underlying a trench slope break defines the landward termination of the active accretionary prism and separates it from the outer high. Active subduction accretion is supported by laterally increasing velocities between the deformation front and the active backstop structure. Seismic velocities of the outer high are moderate along both lines (< 5.8 km s−1 at 20 km depth), suggesting a sedimentary composition. Reduced reflectivity beneath a rugged top basement traced along the outer high of both dip-lines supports a high degree of deformation and material compaction. Several kilometres of sediment has accumulated in the forearc domain, although a distinct morphological basin is only recognized off southern Sumatra and is not developed off Sunda Strait. The bathymetric elevation of the Java shelf that is encountered in the southern Sunda Strait corresponds to increased velocities of a basement high there and is connected to extensional structures of the Sunda Strait transtensional basin. Differences observed in the morphology of the forearc domain are also reflected in the lower crustal structure. Off southern Sumatra, the velocity–depth model clearly indicates a continental-type crust underlying the forearc basin, whereas lower velocities are found beneath the Sunda Strait forearc domain. Off Sumatra, some 3-D constraint on the upper plate structure is gained from the refraction strike-lines, which in addition is supported by synthetic data modelling.