Whole Mantle Structures from Broadband Modeling

9814908 Helmberger这项研究涉及利用全球地震台网和PASSCAL便携式地震仪运动带来的地震数据的革命性改进，以便通过体波和面波技术解析地幔结构。在绘制地幔地震速度的横向变化图方面取得了相当大的进展，表明了地球表面下正在进行的活跃的动力学过程。这项研究结合了长周期面波反演、走时层析成像和详细的全记录建模。从这些涉及完全不同的数据集的不同技术中独立得出的模型的相互比较显示出极大的复杂性，但幸运的是，有一些一致。主要目标是在可以解决的地方调和分歧。需要解决的主要问题是上地幔的不均质性及其延伸到过渡区(向下至670公里)以及与下地幔结构的连接。需要将环太平洋长波向下倾向区定位为更离散的连续地震构造，并可靠地估计P和S异常及其尖锐程度。在动力学模型中大量存在的板屈曲和突然增厚的区域应该在地震中是可识别的。同样，非洲和中太平洋下方的大型慢速构造，尽管在CMB附近建立得很好，但在模式差异很大的较浅深度却不太清楚。研究结果对地球的地球化学、矿物物理和地球动力学模型具有重要的参考价值。

9814908HelmbergerThis research involves the utilization of revolutionary improvements in seismic data, due to the Global Seismic Network and PASSCAL portable seismometer campaigns, in order to resolve mantle structure by means of body wave and surface wave techniques. Considerable progress has been made in mapping out lateral variations in seismic velocity in the mantle, demonstrating the active dynamic processes going on beneath the earth's surface. This research combines long-period surface wave inversion, travel-time tomographic imaging, and detailed whole record modeling. An intercomparison of models independently derived from these varied techniques involving totally different data sets show great complexity but, fortunately, some agreement. The major goal is to reconcile disagreements where resolvable. The major issues to be addressed are upper-mantle heterogeneity and its extension into the transition region (down to 670 km) and connections to lower mantle structures. The long-wavelength circum-Pacific down-willing region needs to be localized into more discrete continuous seismic structures with reliable estimates of P and S anomalies and their sharpness. Zones of slab buckling and abrupt thickening that are so abundant in dynamic models should be identifiable seismically. Similarly, the large-scale slow structures beneath Africa and mid-Pacific, although well established near the CMB, are less well defined at shallower depths where models vary greatly. The results are important as input to geochemical, mineral physical, and geodynamic models of the earth.