'Blind Zone Control' Of Earthquake Early Warning System (EEWS)

The National Project of Seismic Intensity Rapid Reporting and Earthquake Early Warning being underway, study on the fundamental problems associated with the design and optimization of an earthquake early warning system (EEWS) plays an important role for ensuring the proper functioning of such a nationwide, large scale,networked system with strong implications not only for seismic disaster reduction but also for seismic disaster risk reduction.Taking two of the key regions of this National Project, the Central China north-south seismic belt (21.0°-41.50N,97.5°-107.5°E) and the Beijing Capital Circle region (38.5°-41.5° N, 113.5°-120° E),as target regions, this thesis conducted systematic conceptual analysis of the 'blind zone', one of the critical issues in the design and optimization of an EEWS.The thesis tries to conduct the analysis in the context of modern seismology, with the following highlights:1) Considering the real-world situation of seismological observation and interpretation practice,the concept of 'blind zone control' was proposed and analyzed. It was pointed out that surrounding the theoretical 'black (hard)blind zone',there is actually a 'gray (soft) blind zone' which can be controlled and minimized by simply enhancing the density of seismic stations.A semi-quantitative relation among the number of actually triggered stations,the density of station deployment, and the actual 'blind zone' was proposed,which might be of practical importance for the performance evaluation and quality control of either a seismic station network or an EEWS.2) Finite size of an earthquake rupture, one of the key concepts in modern seismology, has significant implication for the design of an EEWS. The thesis discussed this issue by scenario earthquake cases, arguing that an EEWS has the potential to make much greater contribution to the reduction of earthquake disasters which is far beyond the expectation in the view of traditional seismology. The discussion deepens the present understanding of the EEWS design which don't aims at a homogeneous deployment, stressing that near-fault denser EEW station deployment may make the EEWS much more effective during great earthquakes.3) Best/Optimal discriminant function for identifying the near fault strong motion recordings, or the Yamada function, has the potential of fast reporting of the size of an earthquake rupture. Considering the characteristics of an earthquake rupture, and the real world situation that for the majority of the national territory the deployment of strong motion stations is limited, the thesis discussed an alternative (simplified) approach to consider the 1-d propagation of an earthquake rupture, focusing on the fast retrieval of the geometry and directivity of the earthquake fault. Existing of the 'blind zone'may affect the timing of such an approach and in turn the performance of the EEWS, which was also discussed in the thesis.It might be expected that the analysis by the thesis may shed some new lights on the long-lasting debate on the usefulness (or cost-effectiveness) of an EEWS in the view of 'blind zone'. The significance of the discussion lies in illuminating some of the 'blind spots' associated with the 'blind zone',and analyzing the problem of 'blind zone' with the new horizon of modern seismology.