Resolving Earth's Free Oscillation Spectrum: New Data and New Techniques

这项研究包括根据最近的大地震对地球完整的正模谱进行全面的重新评估。可以说，在1994年6月9日的玻利维亚深层大地震之前，观测自由振荡地震学已经进入了一种休眠状态。缺乏大型事件，特别是缺乏大型深层次事件，使得进展变得困难和缓慢。三月份的斐济事件重新燃起了人们的兴趣，因为它是自1970年哥伦比亚事件以来数字记录的最大的深海事件，但它很快被玻利维亚事件所掩盖。玻利维亚的地震不仅比1970年哥伦比亚的地震更大，而且被空前数量的天文台级数字站记录下来。对于那些知道用手工数字化记录哥伦比亚大地震的可能性的人来说，这些新数据有望大大提高我们对地球长周期地震反应的认识。预期这项研究至少将导致：对地核各向异性的严格约束，对地幔中相对P和S速度变化的约束，对三维衰减结构（至少均匀谐波度）的约束，分辨率长度低于100 km的高精度1-D模型，精度为0.1%，以及对长周期地震谱的准确描述，使得更好地确定大事件的长周期源行为成为可能。* * * ? ?

9508113 GILBERT This research involves the complete re-evaluation of the Earth's complete normal-mode spectrum in light of recent large earthquakes. It is fair to say that, before the June 9, 1994, great deep Bolivian earthquake, observational free-oscillation seismology had gone into a state of suspended animation. A lack of very large events and, in particular, the lack of very large deep events made progress difficult and incremental. The Fiji event in March rekindled some interest since it was the largest deep event to be digitally recorded since the 1970 Columbian event, but it was rapidly eclipsed by the Bolivian event. Not only was the Bolivian event bigger than the 1970 Columbian event but it was recorded by an unprecedented number of observatory-quality digital stations. For those who know what is possible with hand-digitized recordings of the Columbian event, the new data promise a quantum improvement in our knowledge of the seismic response of the Earth at long-periods. It is anticipated that this research will lead to, at the minimum: stringent constraints on anisotropy in the core, constraints on the relative P and S velocity variations in the mantle, constraints on 3-D attenuation structure (at least of even harmonic degree), high resolution 1-D models with resolution lengths below 100 km for precisians of 0.1%, and an accurate description of the seismic spectrum at long periods making better determination of long-period source behavior for large events possible. *** ??