Collaborative Research: Strain accumulation and release at the Kuril subduction zone from postseismic observations on the Kuril GPS Array in 2007-2014

合作研究：2007-2014年千岛GPS阵列震后观测中千岛俯冲带的应变积累和释放

• 批准号: 1141792
• 负责人: Mikhail Kogan
• 金额: $ 34万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1141792&HistoricalAwards=false
• 关键词: Collaborative; Research; Strain; accumulation; release

The 1,200-km-long Kuril megathrust in the northwest Pacific Ocean is one of the most seismically active regions on the Earth. It was the last major subduction zone totally unexplored by methods of space geodesy. In 2006?2007, a doublet of great earthquakes in this region partly ruptured one of the most conspicuous gaps in subduction-zone seismic activity (the 15 November 2006 Mw 8.3 thrust event and the 13 January 2007 Mw 8.1 extensional event). A large 15 January 2009 Mw 7.4 thrust earthquake in the same region demonstrated the heightened seismic hazard. The Kuril GPS Array was installed several months before the 2006?2007 earthquakes in collaboration between US and Russian scientists. Observations on the array documented coseismic and postseismic surface deformation following the great Kuril earthquakes. The immediate focus of this final phase of the project is on acquiring irreplaceable, transient postseismic data spanning the time period 2007?2014. This project will continue collaboration between US universities and institutions of the Russian Academy of Sciences.The data from the Kuril GPS Array collected in 2006?2011 allowed us to develop models of coseismic slip and models of postseismic mechanisms. It was shown that most of the postseismic motion was caused by the viscoelastic relaxation of shear stresses in the weak Maxwell viscosity asthenosphere. From experience with other postseismic studies, longer time series will allow us to develop more robust models of postseismic deformation and models of interseismic frictional coupling on the subduction interface. The complete 8-year-long data set is required to address fundamental problems: How much of the strain built up from subduction of the Pacific plate beneath the North American plate (the Sea of Okhotsk) has been released in the 2006 and 2007 Kuril earthquakes coseismically and postseismically? Is it possible to explain postseismic surface deformation at the Kuril subduction zone with the linear viscous mantle or a stress-dependent rheology is required? These problems are especially important after the giant 2011 Mw 9.0 Tohoku earthquake, which made the scientists question the validity of conventional precursors of large earthquakes: location of seismic gaps and location of asperities (patches of high frictional locking at a subduction interface).

西北太平洋长 1,200 公里的千岛巨型逆冲断层是地球上地震最活跃的地区之一。这是最后一个完全未被空间大地测量方法探索过的主要俯冲带。 2006年至2007年，该地区发生的两次大地震部分破坏了俯冲带地震活动中最显着的间隙之一（2006年11月15日Mw 8.3逆冲事件和2007年1月13日Mw 8.1伸展事件）。 2009 年 1 月 15 日同一地区发生的 7.4 级逆冲大地震表明了地震危险性的增加。美国和俄罗斯科学家合作，在 2006 年至 2007 年地震发生前几个月安装了千岛 GPS 阵列。对阵列的观测记录了千岛大地震后的同震和震后表面变形。该项目最后阶段的直接重点是获取 2007 年至 2014 年期间不可替代的瞬态震后数据。该项目将继续美国大学和俄罗斯科学院机构之间的合作。2006年至2011年收集的千岛GPS阵列数据使我们能够开发同震滑移模型和震后机制模型。结果表明，大部分震后运动是由弱麦克斯韦粘性软流圈中剪应力的粘弹性弛豫引起的。根据其他震后研究的经验，更长的时间序列将使我们能够开发更稳健的震后变形模型和俯冲界面上的震间摩擦耦合模型。需要完整的长达 8 年的数据集来解决根本问题：太平洋板块俯冲到北美板块（鄂霍次克海）下方所产生的应变在 2006 年和 2007 年千岛地震中通过同震和震后释放了多少？是否可以用线性粘性地幔来解释千岛俯冲带的震后地表变形，或者需要依赖于应力的流变学？这些问题在 2011 年东北 9.0 级大地震之后尤为重要，这使得科学家们对大地震的传统前兆的有效性产生了质疑：地震间隙的位置和凹凸体的位置（俯冲界面处的高摩擦锁定斑块）。