That 4.0 magnitude earthquake rattled us out of bed at 6:49 this morning might have been the biggest bang of the day (we hope!), but that doesn't mean the Hayward Fault stayed quiet after that. In fact, things kept on shaking until about 8:30, just at a much lower level.
According to the US Geological Survey, the same spot near Piedmont that shook this morning has experienced seven additional aftershocks of note, from a 1.6 at 6:52 to the last, a 1.2 at 8:28. The strongest appeared to be a 2.4 at 7:40, which was apparently felt by around 81 people.
The M4.0 this AM released 1/30,000 the energy of the 1989 M6.9.— Dr. Lucy Jones (@DrLucyJones) August 17, 2015
Of course, what everyone wants to know is if this morning's quake is a sign that something bigger is on the way. The answer? Probably not, but who the hell knows?
“At the moment," USGS geologist David Schwartz tells KQED, "it’s hard to say that this had any greater meaning than we’ve had earthquakes in this general area before.”
Keith Knudsen, Deputy Director of the USGS’s Earthquake Science Center in Menlo Park is a little more comforting. He tells the Chron that “There is a low likelihood that this could be a foreshock. There is a 5-to-10 percent chance that we could have a bigger earthquake in the coming weeks.”
The 6:49 a.m. quake didn't cause any major damage — some folks said things fell off shelves, and the Chron reports that "At least one traffic light at Geary and 20th streets in the Richmond District toppled over" (but maybe that was just pee) — but it felt strong to many. That's because, Knudsen says, “It was relatively shallow and intense for a magnitude 4...People near the epicenter felt more intense than they would if it was deeper.”
All in all, the USGS estimates, about 40,000 people felt a strong jolt and 510,000 felt a moderate rattle in this morning's largest quake. 4.5 million people probably felt weak or light shaking.
And it wasn't just people: though my animals didn't notice a damn thing (they never do!), at least two Bay Area dogs did. Check it out: