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使用区域(NIED MT)和全球(哈佛大学CMT)矩张量目录研究了琉球岛弧和冲绳海槽的应力场。使用NIED MT目录4年数据和哈佛大学CMT目录24年数据的联合数据集,发现沿琉球岛弧弧前分布的平行弧向的扩张应力区域,并观测到详细的冲绳海槽扩张应力场。除北东端外,该顺弧向扩张在整个琉球岛弧区域都可以观测到。该应力场通过火山链与冲绳海槽的弧后扩张应力场明显分开。由于它存在于正俯冲区域以及弱耦合俯冲区域中,倾斜俯冲的影响不足以解释平行弧向扩张的形成。因而,我们认为弧后张开过程应该在这个平行弧向的扩张中起了重要作用。沿冲绳海槽,在琉球岛弧东南部和中部观测到垂直岛弧方向的扩张应力场,而在冲绳海槽东北部,扩张轴的方向既与岛弧的法向斜交又与板块运动方向斜交。考虑了俯冲板块与弧前和弧后相互作用的二维力学模型是不充分的,因为整个琉球岛弧都观测到平行弧向扩张应力场,而且冲绳海槽东北部的扩张轴与海槽走向斜交。倾斜的弧后应力可能发源于弧后下部或者弧后大陆一侧。解释该现象的最简单的方法之一可能是冲绳海槽东北部的活动断裂作用。
The stress field of the Ryukyu Island arc and the Okinawa Trough was studied using the NIED MT and the global (CMT) moment tensor catalogs. Using a joint dataset from the 4-year NIED MT catalog and the Harvard CMT catalog for 24-year data, the area of dilatational stress parallel to the arc pre-arc distribution along the Ryukyu Island was found and the dilatational stress field in the Okinawa Trough was observed. In addition to the north east end, the paraxial expansion can be observed throughout the Ryukyu island arc. The stress field is clearly separated from the post-arc dilatational stress field in the Okinawa Trough by the volcanic chain. Because of its existence in the area of positive subduction and the area of weakly coupled subduction, the influence of oblique subduction is not sufficient to explain the formation of parallel arc expansion. Therefore, we think that the process of backlash should play an important role in the expansion of this parallel arc. Along the Okinawa Trough, the dilatational stress field in the vertical island arc is observed in the southeastern and central parts of the Ryukyu Island arc. In the northeastern part of the Okinawa Trough, the direction of the expansion axis is not only perpendicular to the island arc but also to the direction of plate motion Slanted. Considering the two-dimensional mechanical model of subduction plate interaction with the pre-arc and back-arc, it is not sufficient because the parallel arc-direction dilatational stress field is observed in the entire Ryukyu Island arc and the expansion axis and the trough in northeastern Okinawa Trough Slanted. Tilted backarc stress may originate from the back of the arc or from the back of the arc. One of the easiest ways to explain this phenomenon may be the active fault in the northeastern Okinawa Trough.