| 台湾碰撞带现今地壳变形场特征及其动力学成因的有限单元法模拟研究 |
| |
| 引用本文： | 龙小刚,朱守彪.台湾碰撞带现今地壳变形场特征及其动力学成因的有限单元法模拟研究[J].地球物理学报,2015,58(7):2350-2365. |
| |
| 作者姓名： | 龙小刚 朱守彪 |
| |
| 作者单位： | 1. 中国地震局地壳应力研究所(地壳动力学重点实验室), 北京 100085;2. 中国科学院计算地球动力学重点实验室, 北京 100049 |
| |
| 基金项目： | 北京市自然科学基金项目(8152034),国家自然科学基金(40974020),地震动力学国家重点实验室开放基金(LED2012B01)以及中央级科研院所科研业务专项共同资助(ZDJ2013-21,ZDJ2014-01). |
| |
| 摘 要： | 台湾是菲律宾海板块与欧亚板块会聚、碰撞的产物,区内地质构造复杂,地震频发,变形强烈.为定量研究台湾地区变形特征及其动力学成因,文中运用二维不连续变形体弹性力学的有限单元计算方法,利用台湾地区1995—2005年GPS的观测结果作为边界约束,对台湾地区地壳变形场进行了模拟.计算结果显示,台湾中部地区主要呈压缩状态,但在台湾的东北部及南部地区出现了拉张的变形环境.变形程度最大的区域位于台湾东部海岸山脉及其附近海域,同时,计算给出台湾纵谷断裂滑移速率约为13.8~23.5mm/yr,由于纵谷断裂对变形的吸收,因此变形在纵谷断裂以西及西北地区迅速衰减.此外,计算结果还发现,计算给出的台湾岛上的速度值与GPS观测结果吻合得较好;计算给出的主应力方位与地应力观测及震源机制解结果也颇为一致.由此说明文中的有限元模型是合理的.此外,计算结果还表明,菲律宾海板块向北西方向的推挤,板块边界形状,观音、北康高地的抵阻,冲绳海槽扩张及琉球海沟的向南后撤以及断裂作用等,共同造成了台湾地区现今变形场的主要格局.
|
| 关 键 词： | GPS观测 变形场 动力学成因 有限单元 台湾 |
| 收稿时间： | 2015-01-09 |
Present-day crustal strain field in the Taiwan active collision zone and its geodynamic mechanisms: Insight from FEM simulations |
| |
| LONG Xiao-Gang,ZHU Shou-Biao.Present-day crustal strain field in the Taiwan active collision zone and its geodynamic mechanisms: Insight from FEM simulations[J].Chinese Journal of Geophysics,2015,58(7):2350-2365. |
| |
| Authors: | LONG Xiao-Gang ZHU Shou-Biao |
| |
| Institution: | 1. Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China;2. Key Laboratory of Computational Geodynamics, Chinese Academy of Science, Beijing 100049, China |
| |
| Abstract: | The Taiwan Island is the product of convergence and collision between the Eurasian plate and the Philippine Sea plate, where the geological structure is complex, seismicity is high and deformation is strong. As ongoing arc-continent collision around Taiwan is rare in the world, Taiwan has been described as an ideal natural laboratory for plate collision studies. Taiwan has established its GPS Network since the 1980s, which has cumulated mass data since then and makes it possible to study the crustal deformation in and around it. In order to quantitatively study the characteristics of crustal deformation in Taiwan and to understand their geodynamic mechanisms, we calculated the strain rate field in and around Taiwan by using finite element method (FEM), utilizing GPS data from 1995 to 2005 as boundary constraints in simulation. The heterogeneity of the medium, slippage of the faults and some other factors are taken into consideration to quantitatively study the interseismic deformation in Taiwan and we try to find out the dominant factors that control the deformation. To acquire more ideal computed results, we have taken advantage of the optimal design function of the ANSYS(Design Opt). We take the fitted difference between GPS observations and their corresponding finite element calculated results as objective function, take the material parameters of each subregion and friction coefficients of the faults as design parameters to obtain the optimal finite element model.The computed results of the optimal model show that the largest calculated maximum principal strain of Taiwan is located in the Coastal Range and adjacent waters in eastern Taiwan, the superiority trend of maximum principal compressive strain is NW-SE, which agrees with the orientation of arc-continent collision between the Eurasian plate and the Philippine Sea plate and converges obliquely to Taiwan Island. The computed results also show that contractions are predominant in the central part of Taiwan, while extensions exist in the northeastern and southern parts, respectively. The principal tensile strain rate is larger than the principal compressive strain rate in I-lan Plain, northeast Taiwan, indicating that the region is in the tensile stress environment which may be closely related to the extension of the Okinawa trough. Similarly, tensile stress environment also appears in southern Taiwan. In addition, the azimuths of calculated principal tensile strain are mainly consistent with the directions of the world stress map results and the P and T axes of focal mechanism solutions.The computed velocity fields in Taiwan show a fan shape. The displacement vectors in central and eastern part are in the direction of NW, the direction of velocity changes clockwise towards north and anticlockwise towards south, which reflect the characteristics of Taiwanese materials escaping to northeast and southwest. The Philippine Sea Plate squeezes Taiwan in the direction of NW, but the movement to northwest is blocked by the Kuanyin High(KH) and Peikang High(PH). This may result in the escape phenomenon. In general, the magnitudes of velocities gradually decrease northwestward from about 81.5 mm/yr at Lanyu and Lutao, SE offshore of Taiwan, to nearly no deformation in NW Taiwan. Besides, the simulation results show that most faults are locked(or with large friction coefficients) during interseismic deformation, while the calculated friction coefficient of the Longitudinal Valley Fault (LVF) is 0.5, and the slip rate is about 13.8~23.5 mm/yr. As part of the convergence is absorbed by LVF, deformation west of LVF decays rapidly westwards and northwestwards.Because of the special geology structure in Taiwan region, the crustal strain field is complicated. The calculated results imply that the general framework of present-day deformation in Taiwan results from interactions of many factors such as plate collision between the Eurasian plate and the Philippine Sea Plate, geometry of the plate boundaries, the obstruction of Kuanyin and Peikang high, faulting and rifting, opening of the Okinawa Trough and retreat of the Ryukyu Trench. |
| |
| Keywords: | GPS observation Deformation field Geodynamic mechanism Finite element method Taiwan |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球物理学报》浏览原始摘要信息 |
| 点击此处可从《地球物理学报》下载免费的PDF全文 |
|
