Thread by @SeismoSue

Did you know that the USGS now issues operational aftershock forecasts for significant events? Start with the event page, e.g., URL below, and scroll down to the aftershock forecast link. These forecasts are based on well-established aftershock stats 1/
earthquake.usgs.gov/earthquakes/ev…

although, like snowflakes, no two aftershock sequences are entirely alike, so forecasts can only give statistical likelihood. Initial forecasts use average parameters for a region, but are updated over time based on how productive a given sequence is 2/

12 or so hours after yesterday's M6 Antelope Valley #earthquake, the sequence is on the energetic side, which bumps up chances of more large events: estimated 6% chance of M>6 in the next month, 9% chance of M>6 in the next year 3/

This means that, of past sequences that were like this one statistically, 1 out of 11 of them produced another M6+ quake in the following year. Not expected, but also not that unlikely. The odds of M7+ are much lower, <1% over the next year 4/

Antelope Valley is relatively sparsely populated, but, at a minimum, folks in the immediate area should expect to keep feeling 3s and 4s for a while, and could be hit with something bigger 5/5