Development of a Teleseismic Viscoelastic Waveform Tomography Algorithm with Application to Broadband Seismograms from the Tien Shan

该项目有两个部分：（1）采用R. G.普拉特和同事，迄今为止，专门用于在一个活跃的源环境，以分析记录的地震在1000米的距离（什么是俗称？接收器功能？）以及（2）将该算法应用于最近完成的MANAS项目中在天山采集的宽带地震图集合。 第一部分背后的动机是这种方法的有效性;合理的模型可以在不诉诸大规模并行计算的情况下构建。 所涉及的任务包括将粘弹性版本的这个代码，我们已经开发出，一个伴随反演方案中使用的声学的情况下。 研究人员还将研究纳入各向异性效应并将算法扩展到三维的可行性。 第二部分的动机部分是我们熟悉的MANAS数据集，但更多的是从应用的结果？传统？接收器函数偏移和到达时间层析成像技术。 具体而言，到达时间层析成像图像表明，存在两个高波速板下的天山，这表明在这个地区的板块状岩石圈俯冲的历史悠久。 接收器功能显示，在这些板块似乎被消耗的区域，莫霍面出现了不寻常的中断。 这两个图像都对天山的演化具有一阶意义，但解释的分辨率不够。 基于活动源模拟的波形层析成像方法将显著提高上地幔这些异常特征的成像质量。更好地了解这些特征将对我们估计这一地区的演变和世界这一地区地震活动的根本原因产生重大影响。可以说，我们所拥有的关于地球内部的最佳信息来源是来自地震仪记录的地震记录，这些地震记录在距离震源很远的地方（1000公里）。 在过去十年中，一个特别富有成果的研究领域是对这些地震图中被地震站下方地表几百公里范围内的地球部分修改的部分进行建模。 在这个项目中，研究人员将开发一种新的技术，通过调整方法，从这些类型的波中提取更多的信息，这种方法已被证明在小得多的尺度上的地下成像中非常有用。活跃？比如爆炸和振动器 尽管尺度不同，但模拟波传播所涉及的基本物理学是相同的。 该算法将足够通用，科学家和工程师可以在任何类似的环境中使用，以产生地下图像。

This project has two parts: (1) to adapt a suite of waveform tomography algorithms based on a 2D acoustic framework developed over the past 18 years by R. G. Pratt and co-workers and thus far used exclusively in an active source environment to the analysis of recordings of earthquakes at teleseismic distances (what are commonly known as ?receiver functions?) and (2) to apply this algorithm to a collection of broad band seismograms collected in the Tien Shan as part of the recently completed MANAS project. The motivation behind the first part is the demonstrated efficacy of this approach; reasonable models can be constructed without resorting to massively parallel computing. The tasks involved include incorporating a visco-elastic version of this code, which we have already developed, to an adjoint inversion scheme similar to that used in the acoustic case. The researchers will also investigate the feasibility of incorporating anisotropic effects and extending the algorithm to three-dimensions. The second part is motivated partly by our familiarity with the MANAS dataset, but more by results from the application of ?traditional? receiver function migration and arrival time tomography techniques. Specifically, arrival time tomography images indicate the presence of two high wavespeed slabs beneath the Tien Shan that suggest a long history of plate-like lithospheric subduction in this region. The receiver functions show an unusual disruption in the Moho in the areas where these plates appear to be consumed. Both these images have first order implications for the evolution of the Tien Shan, but interpretations suffer from insufficient resolution. Based on active source analogues, the waveform tomography approach will significantly improve the quality of the images of these unusual features in the upper mantle. A better understanding of these features will have a significant impact on our estimation of both the evolution of this region and the root cause of earthquake activity in this part of the world.Arguably the best sources of information we have about the interior of the Earth are derived from seismograph records of earthquakes recorded at long distances (1000 km) from the source. A particularly fruitful area of research over the past decade has been in modeling those parts of these seismograms that are modified by those parts of the Earth within a few 100 km of the surface beneath a seismic station. In this project the researchers will develop a new technique to extract more information from these types of waves by adapting methodology that has proved to be very useful in subsurface imaging on a much smaller scale using ?active? sources like explosions and vibrators. Despite the difference in scale, the basic physics involved in modeling wave propagation is the samel. The algorithm will be general enough for scientists and engineers to use in any analogous environment to produce subsurface images.