  The MyShake project aims to build a global smartphone seismic network to
facilitate large-scale earthquake early warning and other applications by
leveraging the power of crowdsourcing. The MyShake mobile application first
detects earthquake shaking on a single phone. The earthquake is then confirmed
on the MyShake servers using a "network detection" algorithm that is activated
by multiple single-phone detections. In part two of this two paper series, we
report the first order performance of MyShake's Earthquake Early Warning (EEW)
capability in various selected locations around the world. Due to the present
sparseness of the MyShake network in most parts of the world, we use our
simulation platform to understand and evaluate the system's performance in
various tectonic settings. We assume that 0.1% of the population has the
MyShake mobile application installed on their smartphone, and use historical
earthquakes from the last 20 years to simulate triggering scenarios with
different network configurations in various regions. Then, we run the detection
algorithm with these simulated triggers to understand the performance of the
system. The system performs best in regions featuring high population densities
and onshore, upper crustal earthquakes M<7.0. In these cases, alerts can be
generated ~4-6 sec after the origin time, magnitude errors are within ~0.5
magnitude units, and epicenters are typically within 10 km of true locations.
When the events are offshore or in sparsely populated regions, the alerts are
slower and the uncertainties in magnitude and location increase. Furthermore,
even with 0.01% of the population as the MyShake users, in regions of high
population density, the system still performs well for earthquakes larger than
M5.5. For details of the simulation platform and the network detection
algorithm, please see part one of this two paper series.
