  The Earthquake Network research project implements a crowdsourced earthquake
early warning system based on smartphones. Smartphones, which are made
available by the global population, exploit the Internet connection to report a
signal to a central server every time a vibration is detected by the on-board
accelerometer sensor. This paper introduces a statistical approach for the
detection of earthquakes from the data coming from the network of smartphones.
The approach allows to handle a dynamic network in which the number of active
nodes constantly changes and where nodes are heterogeneous in terms of sensor
sensibility and transmission delay. Additionally, the approach allows to keep
the probability of false alarm under control. The statistical approach is
applied to the data collected by three subnetworks related to the cities of
Santiago de Chile, Iquique (Chile) and Kathmandu (Nepal). The detection
capabilities of the approach are discussed in terms of earthquake magnitude and
detection delay. A simulation study is carried out in order to link the
probability of detection and the detection delay to the behaviour of the
network under an earthquake event.
