  The China Earthquake Administration (CEA) has launched an ambitious
nationwide earthquake early warning (EEW) system project currently under
development, which will include approximately 15,000 seismic stations and be
the largest EEW system in the world. The new EEW system is planned to go online
at the end of 2023. In approximately 50%, 30% and 20% of Chinese mainland, the
inter-station distance will soon be smaller than 50 km, 25 km and 15 km,
respectively. The expected effectiveness of this EEW system can be quantified
via the metric determined from the radius of the blind zone, which refers to
the area near the epicenter where there is insufficient time to issue a warning
before the arrival of strong S- and surface waves. This study uses a
theoretical network-based method together with Monte Carlo simulation to obtain
the spatial distribution of the blind zone radii and their associated
uncertainties for the new seismic network based on its configuration. We find
that the densified new seismic network is expected to have excellent EEW
performance as the area covered by small blind zones with radius less than 30
km increases dramatically from approximately 2% to 22%, that is by 2.4 million
km2 inside Chinese mainland. We also find that every 1,000,000 RMB (about
146,000 USD) invested to densify the planned network will lead to an areal
increase of 3,000 km2 of small blind zones. Continuing to increase the density
of stations in some key regions with blind zone radii ranging from 15 to 40 km
is still necessary to control the unexpected expansion of blind zones due to
possible (and common) stations failure. Our work provides insights into the
expected performance of the upcoming EEW network in Chinese mainland, and our
proposed evaluation approach is broadly applicable for predicting the
performance of EEW systems during their planning, design, and implementation
stages.
