Abstract:Controlling the ‘blind zone’ of an Earthquake Early Warning System(EEWS),that is,to avoid the unexpected/accidental expansion of the ‘theoretical blind zone’ in the real operation of the EEWS,is one of the key issues in the design and implementation of the system. Taking the prototype EEWS of the Beijing Capital Circle region as an example,we analyzed the control of the EEWS ‘blind zone’ for minimizing earthquake disasters. It is pointed out that,if not only travel times but also the finite size of seismic sources,and the failure of seismic stations are taken into account,increasing the density of seismic stations with inter-station distances less than 20km is still useful for controlling the ‘blind zone’. Decreasing the inter-station distance below 20km,although having minor contribution to reducing the size of the ‘blind zone’,plays an important role in significantly improving the performance of the EEWS.