Sarah E. Minson California Institute of Technology Benjamin A. Brooks, Jessica R. Murray U.S. Geological Survey Susan E. Owen Jet Propulsion Laboratory Robert A. Iannucci Carnegie Mellon University – Silicon Valley

EEW and real-time GPS are expanding globally Most high-risk areas still not covered RT GPS EEWEEW

Requires dense networks of scientific instruments Expensive to build and maintain Scientific GPS: $1,000-$7,500 per year, per station Many high-risk areas cannot afford this investment RT GPS EEWEEW

Consumer electronics contain geophysical sensors Smartphones, laptops, tablets, cars What if we could monitor earthquakes with just consumer-quality sensors? RT GPS EEWEEW

This is not what you get from scientific instruments Pseudorange only (no phase information) Single frequency (coarse acquisition) vs. dual frequency Broadcast orbits

Post-processed scientific GPS PseudorangePseudorange

NorthNorthUpUpEastEast StaticStatic PseudorangePseudorange

Count number of stations for which they and their 4 closest neighbors have offsets greater than threshold

5  excursion from background

Displacement amplitude decays with distance Power law fit to observed offsets

S-wave reaches population center 5  exceeded

EEWEEW True Mw NEIC/PTWCNEIC/PTWC PseudorangePseudorange

If we wanted to replace GPS network with iPads: 500 $100 = $50,000 About the cost of installing 1-2 permanent GPS stations To replace GPS network with equal noise: 2,000 $100 = $200,000

We could build a workable early warning network for orders of magnitude less cost… …But really we don’t want to be responsible for the network

We should be using the GPS receivers people already own and maintain Significantly noisier (bad sky view, noisy environment) Potentially orders of magnitude more sensors Marginal cost to build and maintain Built-in way to track location and customize warnings Citizen science

Scientific GPS: Mw 8.9 Best Slip Model: Mw 9.1 Pseudorange: Mw 8.9

Seismic EEW Scientific GPS NEIC/PTWCNEIC/PTWC PseudorangePseudorange True Mw What we are doing What we could do in western U.S. A way forward everywhere else