Collaborative Research: Active Tectonics of Northeast Asia

0106999-0106002-Burgmann0105587-KING东北亚-太平洋、北美和欧亚板块汇聚的地方，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很好地确定。该地区一些较小的微板块，包括鄂霍次克、北极、白令和阿穆里亚板块，使问题变得更加复杂，它们的存在、运动速度和边界仍然不确定。该项目依靠空间大地测量学研究欧亚板块和北美板块的边界、夹在中间的微型板块及其与太平洋板块的相互作用的广阔形变区。这次调查的动机是最近在东西伯利亚、韩国和日本启动了高精度的GPS测量，这为进一步了解这一神秘地区提供了机会。新的GPS测量为构造模型提供了约束，该模型考虑了与板块边界应变积累和释放相关的板块构造角速度和变形。大地测量分析通过仔细整合区域和全球GPS数据，帮助约束从中亚到北美西部的形变运动学。新的测量集中在三个不受当前数据限制的地区：库页岛、东西伯利亚的切尔斯基山脉和堪察加山脉。预期成果将包括欧亚大陆和北美之间旋转极位置的改善(在西伯利亚北部)；更精确地划定东北亚板块边界；以及对鄂霍次克微板块和其他区域块体的存在、位置和现今运动的限制。阻碍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累积的影响。在研究区域内发生大地震(如1995 MW=7.0和2000 MW=6.8 Sakhalin，1997 MW=7.7堪察加地震)的地方，形变场进一步受到同震和震后运动的干扰。因此，这项研究解决了区域板块运动学和俯冲带动力学之间密不可分的联系。弹性和粘弹性模型用于评估地震间应变累积过程，并估计主要板块边界断层上的地震耦合量。该模型允许分离板块边界应变和板块构造角速度对实测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.