Measuring and modeling postseismic deformation processes of Andaman Islands

安达曼群岛震后变形过程的测量和建模

• 批准号: 1417186
• 负责人: John Puchakayala
• 金额: $ 10.87万
• 依托单位: University of Memphis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1417186&HistoricalAwards=false
• 关键词: Measuring; modeling; postseismic; deformation; processes

Nearly a decade after the great (Mw 9.3) Sumatra-Andaman earthquake, the understanding of the post-event processes responsible for relaxation of the co-seismic stress change still remains incomplete. Modeling of early Andaman Islands GPS displacements indicated near-field motions were dominated by slip down-dip of the rupture, but various researchers ascribe elements of relaxation to dominantly poroelastic, dominantly viscoelastic and dominantly fault slip processes, depending primarily on their measurement sampling and the modeling tools used. Intriguingly, uplift and right-lateral horizontal shear deformation, observed in the Andaman data, is exactly opposite the predictions of radially-symmetric viscoelastic relaxation models. We hypothesized then that, either radially-symmetric models neglect heterogeneities in flow properties that are important to understanding the earthquake cycle, or transient slip still dominates the near-field signals years after the event. Modeling of GPS displacements suggests that the twin (M8.6 and M8.2) ruptures of 2012 intra-plate oceanic earthquakes could have possibly accelerated the ongoing slow slip, along the lower portion of the thrust fault beneath the Islands with a month long slip of 4-10 cm. Thus, the continuing postseismic deformation excited by the December 2004 Sumatra-Andaman (Mw = 9.2) co-seismic stress change and interfered by 2012 M8.6 and M8.2 twin earthquake, is the primary objective of this continued work. There is also the need for better models for the near field deformation along the Andaman Islands. Currently there are models that either explain the far field deformation or near field deformation but not both combined.Measurements will continue at five continuous and twelve campaign stations in the Andaman Islands. UNAVCO facility has loaned GPS receivers that are operating in this region. Data from these sites along with surrounding IGS sites will be processed using GAMIT/GLOBK software. PYLITH finite element software will be used to model the post seismic deformation combining both after slip and viscoelastic relaxation due to 2004 co-seismic change and that of 2012 Sumatra twin earthquakes. Data collected will be archived at the UNAVCO facility and is open for all. This endeavor is in collaboration with Jawaharlal Nehru Centre for Advanced Scientific Research Bangalore, India. In the coming year we will initiate the processes to hand over the complete technology transfer to this institute in main land India and to locals in the Andaman Islands to maintain the network of GPS stations. This includes training of the locals and those in JNCASR in Bangalore.

大苏门答腊 - 安达曼地震发生近十年后，对负责放松共同压力变化的事后过程的理解仍然不完整。安达曼群岛早期的GPS位移的建模表明，近落的破裂下降占主导地位，但是各种研究人员将放松的元素归因于主要的毛线弹性，主要是粘弹性的，并且主要取决于其测量采样和测量采样，并主要取决使用的建模工具。有趣的是，在安达曼数据中观察到的抬高和右侧水平剪切变形与径向对称性粘弹性弛豫模型的预测完全相反。然后，我们假设，要么径向对称模型忽略了流动性能中对于理解地震周期很重要的异质性，要么瞬时滑移仍然占据了事件发生后几年的近场信号。 GPS位移的建模表明，2012年板内海洋地震的双胞胎（M8.6和M8.2）破裂可能会加速持续的慢速滑移，沿着岛屿下方的下部断层的下部，并带有一个月的滑动。 4-10厘米。因此，2004年12月的苏门答腊 - 安达曼（MW = 9.2）的共同应激变化持续的后视事件变形，并在2012年M8.6和M8.2 Twin地震上干涉，这是这项持续工作的主要目标。还需要更好的模型来实现安达曼群岛沿线的近场变形。目前，有一些模型可以解释远处的野外变形或近场变形，但并非都合并。计量将继续在安达曼群岛连续五个连续和十二个竞选站。 UNAVCO设施已借贷该地区正在运行的GPS接收器。这些站点的数据以及周围的IGS网站将使用游戏/Globk软件进行处理。 Pylith有限元软件将用于对后的地震变形进行建模，结合了由于2004年的共同变化和2012年Sumatra Twin Twin地震而引起的滑动和粘弹性松弛。收集的数据将在UNAVCO设施存档，并为所有人开放。这项努力与印度班加罗尔高级科学研究中心合作。在来年，我们将启动这些过程，将完整的技术转移移交给印度主要土地的该研究所，并将安达曼群岛的当地人交给维持GPS站网络的当地人。这包括对当地人和班加罗尔JNCASR的培训。