The Structure of the Crust and Lithosphere of the Antarctic Plate

9615139 Ritzwoller摘要本奖项支持对横跨南极和南大洋传播的宽带(20-200秒)瑞利波和乐夫波的频散特性(群和相速度、幅度和极化)的研究，并为更高分辨率(横向：~500公里)的南极板块地壳和岩石圈模型反演这些测量结果。在很大程度上，这项研究将建立在已有的方法和数据资源的基础上。在以前的工作中，人们开发了可靠的频率-时间滤波方法来测量大数据集上的宽带表面波色散。这些经典的方法被系统地应用于欧亚大陆，并正在产生欧亚大陆地壳和岩石圈的高分辨率图像。第二，现在有一个庞大的、稳步增长的、易于访问的南高纬度大震级地震的地震图数据库，这些地震是用宽带数字仪器观测的，这些仪器已经部署在南极洲、南部海洋岛屿以及南美洲南部、非洲和澳大利亚(例如，GDSN、IDA、IRIS/GSN、GTSN、GEOSCOPE、AGSO、Poseidon、MedNet等)。将这些现有技术应用于大量高质量的宽带数据，有望获得有关南极板块之下的地壳和岩石圈的重要新信息。作为这项研究的先导，从IRIS的DMC和GEOSCOPE收集了1977-1995年中期的数据。分析了这些数据的一个子集(从1990年到1995年中期约500个事件)，得到了20秒到150秒周期内南极板块上的初步群速度图。这些初步地图提供了关于下列问题(除其他许多问题外)的新信息：(1)西南极的岩石圈伸展和裂谷，(2)东南极克拉通的范围和性质，以及(3)澳大利亚-南极不整合下面的“异常”上地幔的性质。该奖项支持的新研究将把这些测量扩展到更大的波形数据集，以提高可靠性和分辨率。此外，还将开发更精确的光线跟踪方法，并将其应用于优化横向分辨率。最终的产品将是南极板块下方约150公里深度的剪切速度模型。一旦这些模型建成，与活跃在该区域的南极地球科学家的合作将有助于对它们的解释。

9615139 Ritzwoller Abstract This award supports a study of the dispersion characteristics (group and phase velocity, amplitude, and polarization) of broadband (20 - 200 second) Rayleigh and Love waves propagating across Antarctica and the southern oceans and to invert these measurements for higher resolution (lateral: ~500 km) `tectonic scale' crustal and lithospheric models of the Antarctic Plate. For the most part this research will be built upon already existing methodological and data resources. In previous work, reliable frequency-time filtering methods were developed for measuring broad band surface wave dispersion on large data sets. These classical methods were applied systematically across Eurasia and are yielding high resolution images of the Eurasian crust and lithosphere. Second, there now exists a large, steadily growing, and easily accessible data base of seismograms following large magnitude high southern latitude earthquakes observed on broad band digital instruments that have been emplaced in Antarctica, on southern oceanic islands, and in southern South America, Africa and Australia (e.g., GDSN, IDA, IRIS/GSN, GTSN, GEOSCOPE, AGSO, POSEIDON, MEDNET, etc.). The application of these existing techniques to large volumes of high quality broad band data promises to yield significant new information about the crust and lithosphere underlying the Antarctic Plate. As a lead-in to this research, data were accumulated from IRIS's DMC and GEOSCOPE covering the years 1977 - mid-1995. A subset of these data (~500 events from 1990 to mid-1995) were analyzed to yield preliminary group velocity maps across the Antarctic Plate from 20 second to 150 second period. These preliminary maps provide new information about the following issues (among numerous others): (1) lithospheric extension and rifting in the West Antarctic, (2) the extent and nature of the East Antarctic Craton, and (3) the nature of the `anomalous' upper mantle underlying the Austra lian - Antarctic discordance. The new research supported by this award will extend these measurements to a much larger waveform data set in order to improve reliability and resolution. In addition, more accurate ray tracing methods will be developed and applied to optimize lateral resolution. The ultimate product will be a shear velocity model underlying the Antarctic Plate to a depth of about 150 km. Collaborations with Antarctic geoscientists active in the region will facilitate the interpretation of these models once they are constructed.