Simulated M8 Earthquake Rupturing in Northern California

The 2 panels show 2 snapshots in time as a simulated M8 earthquake ruptures from just offshore on the northern San Andreas fault southward toward San Francisco. Panel 1 shows the moment in time when someone in San Francisco would receive a notification if they wanted to get alerts for potential shaking of 2%g or greater. This is the threshold at which most – but not all – people would feel some shaking, and below the threshold for damage. At this alerting level, the earthquake would have already grown to a magnitude (M) level of 7, and there would be 48 seconds of warning before shaking arrived at their location. If instead they did not want to be alerted until they were sure they would experience shaking of 22%g (corresponding to very strong shaking and moderate potential for damage) they would only receive 8 seconds of warning (panel 2).