Fine Scale Structure of the Upper Mantle Using Array Technologies

700公里处地球上地幔向下至地幔过渡带深度的内部边界(地震间断)包含有关地球内部的热、成分和动力学状态的重要信息。对地球这一区域的高分辨率研究为这颗行星的内部活动提供了重要的制约因素。大多数上地幔和过渡带研究的是中长波(500-1000公里)的图像结构，因此缺乏对较短尺度(10‘S公里或以下)的结构研究的分辨率。这项建议的重点是利用地震台阵数据和台阵处理技术来提高该地区的精细分辨率。地震台阵是一个地震计网络，它可以通过时间序列叠加来分析地球结构，以提高相干到达信号的信噪比，而不是非相干能量。改进的信噪比允许在短尺度长度下研究地球结构。阵列可以测量波场的入射角，因此可以更好地描述和识别相位。使用澳大利亚(Warramunga阵列)和印度(Gauribitanur阵列)的两个阵列的数据，我们针对三个主要目标：1)通过对澳大利亚和印度下面的预波复制的阵列分析，解决410公里和660公里不连续的细尺度结构；2)利用PP散射研究海洋下210公里不连续的性质；3)通过PTO-P和S反射和转换来探测、表征和模拟最高下地幔的反射体。使用包括两个阵列记录的数百次地震的大型数据集，我们将给出澳大利亚北部和印度北部和东北部的前所未有的分辨率。较高的分辨率将有助于对矿物物理和地球动力学含义进行更直接的比较，包括地幔中水的分布、地幔过渡带不连续的主要特征(厚度、地震速度梯度和不连续尖锐程度)、520公里处是否存在中等深度不连续以及410公里以上部分熔融物质的存在。

The internal boundaries (seismic discontinuities) of Earth's upper mantle down todepths of the mantle transition zone at 700 km contain important information aboutthe thermal, compositional and dynamical state of the Earth's interior. High resolutionstudies of this region of the Earth provide important constraints on the internal worksof this planet. Most upper mantle and transition zone studies image structure atintermediate to long wavelength (500 - 1000 km), thus lacking resolution to studystructure at shorter scales (10's km or less). This proposal focuses on using seismicarray data and array processing technologies to improve fine scale resolution of thisregion. A seismic array is a seismometer network that permits analysis of Earthstructure though time series stacking to enhance signal to noise ratios of coherentarrivals over incoherent energy. Improved signal to noise ratios allows studying Earthstructure at short scale lengths. Arrays permit measurement of the incidence angle ofthe wavefield, therefore allowing better phase characterization and identification.Using data from two arrays located in Australia (Warramunga Array) and India(Gauribidanur Array) we target three main objectives: 1) Resolving fine scalestructure of the 410-km and 660-km discontinuities through array analysis of the Pwavetriplication beneath Australia and India; 2) Studying the nature of the 210-kmdiscontinuity beneath oceanic regions using PP scattering; 3) Detection,characterization and modeling of reflectors in the uppermost lower mantle through Pto-P and S-to-P reflections and conversions. Using a large dataset including hundredsof earthquakes recorded at the two arrays will give us an unprecedented resolutionbeneath northern Australia and beneath north and northeast India. The higherresolution will facilitate a more direct comparison to mineral physical andgeodynamical implications including the distribution of water in the mantle, keyfeatures of the mantle transitions zone discontinuities (thickness, seismic velocitygradient, and discontinuity sharpness), the presence or absence of an intermediatedepth discontinuity at 520-km and the existence of partially molten material above410-km depth.