Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, 14467, Potsdam, Germany.
University of Potsdam, Potsdam, Germany.
Sci Rep. 2019 Jan 30;9(1):981. doi: 10.1038/s41598-018-37524-4.
Shear-waves are the most energetic body-waves radiated from an earthquake, and are responsible for the destruction of engineered structures. In both short-term emergency response and long-term risk forecasting of disaster-resilient built environment, it is critical to predict spatially accurate distribution of shear-wave amplitudes. Although decades' old theory proposes a deterministic, highly anisotropic, four-lobed shear-wave radiation pattern, from lack of convincing evidence, most empirical ground-shaking prediction models settled for an oversimplified stochastic radiation pattern that is isotropic on average. Today, using the large datasets of uniformly processed seismograms from several strike, normal, reverse, and oblique-slip earthquakes across the globe, compiled specifically for engineering applications, we could reveal, quantify, and calibrate the frequency-, distance-, and style-of-faulting dependent transition of shear-wave radiation between a stochastic-isotropic and a deterministic-anisotropic phenomenon. Consequent recalibration of empirical ground-shaking models dramatically improved their predictions: with isodistant anisotropic variations of ±40%, and 8% reduction in uncertainty. The outcomes presented here can potentially trigger a reappraisal of several practical issues in engineering seismology, particularly in seismic ground-shaking studies and seismic hazard and risk assessment.
剪切波是地震辐射出的最具能量的体波，是工程结构破坏的罪魁祸首。在短期应急响应和长期灾害韧性建筑环境风险预测中，准确预测剪切波幅度的空间分布至关重要。尽管几十年前的理论提出了一种确定性的、高度各向异性的四叶剪切波辐射模式，但由于缺乏令人信服的证据，大多数经验性的地面震动预测模型还是采用了过于简化的各向同性随机辐射模式。如今，我们利用全球范围内专门为工程应用而收集的经过统一处理的、具有代表性的大量地震记录数据集，揭示、量化和校准了剪切波辐射从随机各向同性到确定性各向异性现象的频率、距离和断层类型依赖性转变。对经验性地面震动模型的相应重新校准显著提高了它们的预测能力：等距各向异性变化幅度为±40%，不确定性降低了 8%。这里呈现的结果可能会引发工程地震学中几个实际问题的重新评估，特别是在地震地面震动研究和地震灾害风险评估中。
