菲律宾海板块的整体旋转线性应变模型与板内形变-应变场
李延兴1 张静华1 何建坤2 李 智3 郭良迁1 张中伏1 张俊青1
1.中国地震局第一监测中心,天津 300180
2.中国科学院地质与地球物理研究所,北京 100101
3.装备技术指挥学院,北京 101416
摘 要 用菲律宾海板块上7个站ITRF2000的速度建立了菲律宾海板块的整体旋转线性应变模型。菲律宾海板块的现今运动是顺时针方向旋转,与NNR-NUVEL-1A估计的旋转方向是一致的,但与NNR-NUVE-1A估计的旋转极位置和旋转角速度有较大差别。本文模型与Sell a等建立的刚体运动模型相比能更精确地描述菲律宾海板块的现今构造运动与板内形变。菲律宾海板块内部存在强烈的形变-应变场。在板块上存在一致的向东形变,形变速率是中央构造线附近小,东、西边界附近大,南、北两端小,中部大,在Mariana弧上向东的形变速率达到48.4mm/yr。板块上南北方向的形变,东、西部存在明显差别,东部的南北向形变速率很小,西部在Manila海沟附近南北向形变速率较大,北端向北的形变速率为11.3mm/yr,南端向南的形变速率为29.3mm/yr。板块的中央构造线把板块的主应变场分为东、西两个区。东区存在非常强烈的张应变,压应变则很弱。主张应变为近东西方向,从中央构造线向东主张与主压应变率逐渐增加,板块东南边界附近（148ºE,15ºN）主张应变率最大为8.58×10-8/yr。在西区,存在很强的主压应变而主张应变则较弱,主压应变为NW-SE方向,主压与主张应变率从中央构造成向西逐渐增加,在板块西北边界（122ºE,23ºN）附近,主压应变率最大为5.71×10-8/yr。菲律宾海板块主应变场的空间变化与板块内部及周围的构造背景密切相关,是构造应力场的反映。
关键词 菲律宾海板块 整体旋转 线性应变 板内形变 应变场
INTEGRAL-ROTATION LINEAR STRAIN MODEL AND
INTRAPLATE DEFORMATION-STRAIN FIELD
OF THE PHILIPPINE SEA PLATE
LI Yan-xing 1 ZHANG Jing-hua 1 HE Jian-kun 2 LI Zhi 3 GUO Liang-qian 1
ZHANG Zhong-fu 1 ZHANG Jun-qing 1
1 First Crust Monitoring and Application Center, China Earthquake Administration, Tianjin 300180, China
2 Institute of Equipment Technology and Command, Beijing 101416, China
3 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101, China
Abstract In the paper, we create an integral-rotation linear strain model for the Philippine Sea plate (PHIL) on the basis of the ITRF2000 velocities of 7 sites on the PHIL. Our study shows that the current-day tectonic movement of the PHIL is clockwise, which is consistent with the rotational direction estimated by the NNR-NUVEL-1A, but quite different from the pole position and angular velocity from the NNR-NUVEL-1A. Compared with the rigid motion model created by Sella, et al., our model is capable to accurately describe the current-day tectonic movement and intraplate deformation of the PHIL. There is an intensive deformation–strain field within the PHIL. The plate exists consistent eastward deformation: the deformation rate is small near the central tectonic line and large close to the east and west boundaries; small at the south and north ends and large in the central part. The eastward deformation rate of the Mariana arc is at a minimum value of 48.4 mm/yr. The NS-trending deformation differs greatly in the eastern and western parts, which is very small in the eastern part and relatively large near the Manila trench in the western part; the northward deformation rate is 11.3 mm/yr at the north end and the southward deformation rate is 29.3 mm/yr at the south end. The principal strain field of the PHIL is divided into the eastern and western areas by the central tectonic line. In the eastern area, the tensile strain is very intensive, while the compressive strain is very weak. The principal tensile strain is in the proximate EW-direction. The principal tensile and compressive strain rates increase gradually from the central tectonic line to the east and the principal tensile strain rate reaches the highest value of 8.57×10-8/yr near the southeast boundary (148ºE, 15ºN). In the western area, the principal compressive strain is strong, the principal tensile strain is relatively weak, and the principal compressive strain is in the NW-SE direction. From the central tectonic line to the west, the principal compressive and tensile strain rates increase gradually and the principal compressive strain rate reaches a maximum value of 5.69×10-8/yr near the northwest boundary (122ºE, 23ºN). Closely related to the intraplate and surrounding tectonic settings, the spatial variation of the principal strain field of the PHIL is a reflection of the tectonic stress field.
Key words Philippine Sea plate, integral rotation, linear strain, intraplate deformation, strain field