走滑断层对洋中脊热结构与流动场的影响规律及对太平洋南部边界RRF型三联点的解释

王振山; 魏东平; 徐佳静; 王少坡

doi:10.11939/jass.20180009

走滑断层对洋中脊热结构与流动场的影响规律及对太平洋南部边界RRF型三联点的解释

王振山^1,2,
魏东平^1,2, ,,
徐佳静^1,2,
王少坡^1,2

1.
中国北京 100049 中国科学院计算地球动力学重点实验室
2.
中国北京 100049 中国科学院大学地球与行星科学学院

基金项目: 国家自然科学基金（41474086，41874115）和中国科学院与国家外国专家局创新团队国际合作伙伴计划项目（KZZD-EW-TZ-19）共同资助

详细信息

通讯作者:
魏东平: e-mail：dongping@ucas.ac.cn

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出版历程
- 收稿日期: 2018-03-07
- 修回日期: 2019-03-21
- 网络出版日期: 2019-07-02
- 发布日期: 2019-06-30

Effects of the strike-slip fault on the thermal structure and mantle flow of the mid-ocean ridge and the interpretation to RRF triple junctions at the southern Pacific boundary

1.
Key Laboratory of Computational Geodynamics，China Academy of Sciences，Beijing 100049，China
2.
College of Earth and Planetary Science，University of Chinese Academy of Sciences，Beijing 100049，China

摘要

摘要: 选取太平洋板块南部边界的板块相对运动速度不同的两个洋脊－洋脊－转换断层（RRF）型三联点，即麦夸里（Macquarie）三联点和南太平洋三联点，为研究对象，通过数值模拟的方法，研究该类型三联点走滑断层边界两侧的板块相对运动速度对三联点附近地区地幔流动场和温度结构的影响。模拟结果表明：太平洋南部边界RRF三联点走滑断层边界两侧的板块相对运动速度控制着三联点附近的温度分布和地幔流动；随着走滑断层边界两侧板块相对运动速度的增加，转换断层相对滑动速度增加，温度上升，距洋脊边界100 km范围内的地幔流体速度变大；麦夸里三联点和南太平洋三联点处3个板块的相对运动，使得三联点的转换断层边界浅部产生剪应力集中，导致震源深度集中在15—25 km；同时相对运动产生的地幔流动引起温度结构变化，该变化控制着地形变化。
- 走滑断层 /
- RRF型三联点 /
- 温度结构 /
- 数值模拟
Abstract: Triple junction provides a natural place for studying the interaction of plates. In this paper, we chose two ridge-ridge-fault （RRF） triple junctions with different relative plate velocities at the southern boundary of the Pacific Plate, namely, the Macquarie triple junction and the South Pacific triple junction. We studied the effects of relative plate velocity of the strike-slip fault on the mantle flow and temperature structure of the RRF triple junction by numerical simulation method. We can conclude the following results: ① The relative plate velocity of the strike-slip fault of RRF triple junctions at the southern boundary of the Pacific controls the mantle flow and temperature distribution near triple junctions. ② With increase of the relative plate velocity of the strike-slip fault, the slip velocity of the transform fault and the temperature increases, while the effect on the velocity distribution of mantle fluid concentrates within 100 km from the boundary of the ridge. ③ The relative movement of the three plates at the Macquarie triple junction and the South Pacific triple junction makes the shear stress concentrate in the shallow boundary of the transform fault, which results in the centralized distribution of earthquakes with focal depth in a range of 15−25 km. ④ The topography is mainly controlled by the change of the mantle temperature from the mantle flow caused by the relative motion of plates.
- strike-slip fault /
- RRF triple junction /
- temperature structure /
- numerical modeling

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图 1 三联点分布图

（a）全球三联点分布图；（b）麦夸里三联点地形图；（c）南太平洋三联点地形图① 智利三联点；② 南太平洋三联点；③ 加拉帕戈斯三联点；④ 巴拿马三联点；⑤ 加勒比－北美－科库兹三联点；⑥ 墨西哥三联点；⑦ 里维拉三联点；⑧ 门多西诺三联点；⑨ 夏洛特皇后三联点；⑩ 勘察加－阿留申三联点；⑪ 博索三联点；⑫ 所罗门群岛三联点；⑬ 麦夸里三联点；⑭ 罗德里格斯三联点；⑮ 索马里－阿拉伯－印度三联点；⑯ 阿法尔三联点；⑰ 卡尔奥瓦三联点；⑱ 亚速尔三联点；⑲ 布维三联点

Figure 1. The distribution map of triple junctions

（a） The distribution of global triple junctions；（b） The topography of Macquarie triple junction；（c） The topography of South Pacific triple junction① Chile triple junction；② South Pacific triple junction；③ Galapagos triple junction；④ Panama triple junction；⑤ Caribbean-North America-Cocos triple junction；⑥ Mexico triple junction；⑦ Rivera triple junction；⑧ Mendocino triple junction；⑨ Queen Charlotte triple junction；⑩ Kamchatka-Aleutian triple junction；⑪ Boso triple junction；⑫ Solomon Islands triple junction；⑬ Macquarie triple junction；⑭ Rodrigues triple junction；⑮ Somalia-Arabia-India triple junction；⑯ Afar triple junction；⑰ Karlıova triple junction；⑱ Azores triple junction；⑲ Bouvet triple junction

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图 2 RRF型三联点模型示意图

Figure 2. The schematic diagram of the RRF triple junction model

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图 3 模型1的温度结构

（a）三维温度结构；（b）温度结构剖面图

Figure 3. The temperature structure of model one

（a） Three dimensional temperature structure；（b） The profiles of temperature structure

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图 4 模拟温度与计算所得30 km深处的温度对比图

Figure 4. Comparison of simulation temperature with calculation temperature at 30 km depth

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图 5 模型1—9的温度对比图

（a）沿着断层方向；（b）垂直于断层方向

Figure 5. The temperature contrast diagram of model 1−9

（a） Along the transform fault；（b） Perpendicular to the transform fault

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图 6 模型1垂向地幔流体速度场

（a）三维垂向速度场；（b）垂向速度场剖面图

Figure 6. The vertical velocity of model one

（a） Three dimensional vertical velocity field；（b） The profiles of vertical velocity field

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图 7 模型1—9在45 km深处的垂向地幔流体速度对比图

（a）沿着断层方向；（b）垂直于断层方向

Figure 7. The vertical mantle flow velocity comparison of model 1−9 at the depth of 45 km

（a） Along the transform fault；（b） Perpendicular to the transform fault

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图 8 转换断层地形对比图

（a）麦夸里三联点地形及地震震源机制图；（b）图（a）中AB剖面的观测地形与模拟地形对比图，蓝色虚线对应着转换断层边界与海沟的交点，即图（a）中的C点；（c）南太平洋三联点地形及地震震源机制图；（d）图（c）中AB剖面的观测地形与模拟地形对比图，蓝色虚线对应着转换断层边界的实际起点，即图（c）中的C点。地形数据引自Amante和Eakins （2009），地震数据引自Dziewonski et al （1981）和Ekström et al （2012）

Figure 8. The contrast map of topography for the transform faults

（a） The topography and focal mechanisms of Macquarie triple junction；（b） The contrast map of the simulated and observed topography of profile AB in Fig. （a），the blue dashed line is the intersection between the transform fault and the trench，i.e.，the point C in Fig. （a）；（c） The topography and focal mechanisms of South Pacific triple junction；（d） The contrast map of the simulated and observed topography of the profile AB in Fig. （c），the blue dashed line is the actual starting point of the transform fault， i.e.，the point C in Fig. （c）. The topographic data is after Amante and Eakins （2009），the earthquake data is after Dziewonski et al （1981） and Ekström et al （2012）

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图 9 转换断层等温线剖面图及其对应的剪应力分布

（a）麦夸里三联点转换断层边界等温线剖面图；（b）图（a）剖面对应的剪应力分布图；（c）南太平洋三联点转换断层边界等温线剖面图；（d）图（c）剖面对应的剪应力分布图

Figure 9. The isothermal profile of the transform fault and its corresponding shear stress distribution

（a） The isothermal profile of the transform of the Macquarie triple junction；（b） The shear stress distribution of the profile in Fig. （a）；（c） The isothermal profile of the transform fault of the South Pacific triple junction；（d） The shear stress distribution of the profile in Fig. （c）

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表 1 模型参数（Behn et al，2007；Georgen，2008）

Table 1 Reference parameters of the model （Behn et al，2007；Georgen，2008）

ρ₀/（kg·m⁻³）	α/K⁻¹	η₀/（Pa·s）	η_max/（Pa·s）	μ	k/[W·（m·K）⁻¹]
3 300	3×10⁻⁵	1×10¹⁹	1×10²³	0.6	3

C_P/[J·（kg·K）⁻¹]	T₀/℃	T_m/℃	C₀/MPa	R/[J·（mol·K）⁻¹]	E/（kJ·mol⁻¹）
1 200	0	1 300	10	8.314 4	260

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表 2 模型板块相对运动速度

Table 2 The relative velocities of plates in the models

模型	R₁/（cm·a⁻¹）	R₂/（cm·a⁻¹）	F/（cm·a⁻¹）	模型	R₁/（cm·a⁻¹）	R₂/（cm·a⁻¹）	F/（cm·a⁻¹）
1	3	6	3	6	6	12	6
2	3	9	6	7	6	15	9
3	3	12	9	8	2	4	2
4	3	15	12	9	5	8	3
5	6	9	3
注：R₁，R₂，F分别为代表模型中慢速扩张洋脊、快速扩张洋脊和转换断层。

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