Seismologists caution that if one crucial improvement isn't made, a new earthquake early warning system might not correctly deliver alerts that shaking is approaching certain regions.

Depending on where a powerful magnitude 9 earthquake begins along the Pacific Northwest coast, seismologists at the University of Washington worry that large population areas like Seattle and Tacoma may not get timely signs that shaking is on the way.

Based on their research, Mika Thompson, a PhD student, and Renate Hartog, network manager for the Pacific Northwest Seismic Network, have new recommendations.