Collaborative Research: Active Tectonics of Northeast Asia

东北亚是太平洋、北美和欧亚板块交汇的地方，是板块构造的最后前沿之一。北美-欧亚板块边界的位置尚未确定。该地区的一些较小的微板块，包括鄂霍次克、北极、白令海和阿姆里亚板块，使问题进一步复杂化，这些板块的存在、运动速度和边界仍然不确定。该项目依靠空间大地测量学来研究包括欧亚板块和北美板块边界、中间微板块以及它们与太平洋板块的相互作用的广泛变形带。这项调查的动机是最近在西伯利亚东部、韩国和日本开始的高精度GPS测量，这为了解这一神秘地区提供了重大进展的机会。新的GPS测量为构造模型提供了约束条件，这些模型考虑了板块构造角速度和与板块边界应变积累和释放相关的变形。通过仔细整合区域和全球GPS数据，大地测量分析有助于约束从中亚到北美西部的形变运动学。新的测量集中在目前数据没有很好限制的三个地区：库页岛、西伯利亚东部的切尔斯基山脉和堪察加半岛的尖端。预期结果将包括欧亚大陆和北美之间的旋转极位置（西伯利亚北部）的改善；更精确地圈定东北亚板块边界；以及鄂霍次克微板块和其他区域块体的存在、位置和现今运动的制约因素。阻止直接反演刚性板块运动的GPS速度的主要问题是，许多GPS站的位移受到沿板块边界断层，特别是沿太平洋俯冲边缘的地震间应变积累的影响。大地震（如1995年Mw = 7.0和2000年Mw = 6.8库页岛地震，以及1997年Mw = 7.7堪察加地震）发生在我们的研究区域内，变形场进一步受到同震和震后运动的干扰。因此，该研究解决了密不可分的区域板块运动学和俯冲带动力学。采用弹性和粘弹性模型来评价地震间应变积累过程和估计主要板块边界断层的地震耦合量。模拟允许分离板块边界应变和板块构造角速度对测量的GPS速度场的贡献。

0106999 - Scholz0106002 - Burgmann0105587 - KingNortheast Asia, where the Pacific, North American, and Eurasian plates come together, is one of the last frontiers of plate tectonics. The location of the North America - Eurasia plate boundary is not well established. The problem is further complicated by a number of smaller microplates in the region, including the Okhotsk, Arctic, Bering, and Amurian plates, whose existence, rates of motion, and boundaries are still uncertain. This project relies on space geodesy to study the broad zone of deformation encompassing the boundary of the Eurasian and North American plates, intervening microplates, and their interaction with the Pacific plate. This investigation is motivated by the recent initiation of high-precision GPS measurements in eastern Siberia, Korea, and Japan, which provide the opportunity for a significant advance in understanding of this enigmatic region. New GPS measurements provide constraints for tectonic models, which take into account plate tectonic angular velocities and deformation associated with strain accumulation and release at the plate boundaries.The geodetic analysis helps constrain the kinematics of deformation from central Asia to western North America through careful integration of regional and global GPS data. New measurements focus on three areas not well constrained by current data: Sakhalin, the Cherskiy Range in eastern Siberia, and the Kamchatka cusp. Expected results will include an improved location (in northern Siberia) of the pole of rotation between Eurasia and North America; more precise delineation of plate boundaries in northeast Asia; and constraints on the existence, location and present-day motion of the Okhotsk microplate and other regional blocks.The major problem preventing a straightforward inversion of GPS velocities for rigid plate motions is that displacements of many GPS stations are affected by inter-seismic strain accumulation along plate boundary faults, especially along the Pacific subduction margin. Where large earthquakes (such as the 1995 Mw = 7.0 and 2000 Mw = 6.8 Sakhalin, and the 1997 Mw = 7.7 Kamchatka events) occurred within our study region, the deformation field is further disturbed by co-seismic and post-seismic motions. Thus, the investigation addresses the inextricably linked regional plate kinematics and subduction zone dynamics. Elastic and visco-elastic models are used to evaluate the inter-seismic strain accumulation process and to estimate the amount of seismic coupling on major plate boundary faults. The modeling allows for separation of the contributions of plate boundary strain and plate tectonic angular velocities to the measured GPS velocity field.