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Estimating Crustal Heterogeneity from Double-difference Tomography

机译:从双差层析成像估计地壳的非均质性

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Seismic velocity parameters in limited, but heterogeneous volumes can be inferred using a double-difference tomographic algorithm, but to obtain meaningful results accuracy must be maintained at every step of the computation. MONTEILLER et al. (2005) have devised a double-difference tomographic algorithm that takes full advantage of the accuracy of cross-spectral time-delays of large correlated event sets. This algorithm performs an accurate computation of theoretical travel-time delays in heterogeneous media and applies a suitable inversion scheme based on optimization theory. When applied to Kilauea Volcano, in Hawaii, the double-difference tomography approach shows significant and coherent changes to the velocity model in the well-resolved volumes beneath the Kilauea caldera and the upper east rift. In this paper, we first compare the results obtained using MONTEILLER et al.'s algorithm with those obtained using the classic travel-time tomographic approach. Then, we evaluated the effect of using data series of different accuracies, such as handpicked arrival-time differences (``picking differences''), on the results produced by double-difference tomographic algorithms. We show that picking differences have a non-Gaussian probability density function (pdf). Using a hyperbolic secant pdf instead of a Gaussian pdf allows improvement of the double-difference tomographic result when using picking difference data. We completed our study by investigating the use of spatially discontinuous time-delay data.
机译:可以使用双差断层扫描算法推断有限但非均质体积中的地震速度参数,但是要获得有意义的结果,必须在计算的每个步骤中都保持精度。 MONTEILLER等。 (2005年)设计了一种双差断层扫描算法,该算法充分利用了大型相关事件集的互谱时间延迟的准确性。该算法对异构介质中的理论传播时间延迟进行了精确计算,并基于优化理论应用了合适的反演方案。当应用于夏威夷的基拉韦厄火山时,双差断层扫描方法显示了在基拉韦厄火山破火山口和上东裂谷以下分辨率良好的体积中速度模型的显着且连贯的变化。在本文中,我们首先将使用MONTEILLER等人的算法获得的结果与使用经典行进时间层析成像方法获得的结果进行比较。然后,我们评估了使用不同精确度的数据序列(如手工选择的到达时间差异(``选择差异''))对双差断层扫描算法产生的结果的影响。我们证明挑选差异具有非高斯概率密度函数(pdf)。使用双曲正割pdf而不是高斯pdf可以改善在使用分拣差异数据时的双差断层扫描结果。我们通过调查空间不连续的时延数据的使用来完成我们的研究。

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