3am M3.4 earthquake in St. Helens Seismic Zone

January 25, 2012

by John Vidale

 Here's a seismogram from nearby borehole station B201, click to expand.  Visible are the mainshock and 6 or 7 aftershocks in the following hour.  The latest and largest aftershock is M1.4 (probably there will be more small events, but I'm going back to sleep now - you can check here).  UTC is 8 hours ahead of Pacific Standard Time. So the mainshock is at 2:51am PST and the aftershock is at 3:22am.

The events locate on the St. Helens seismic zone, a location of persistent seismicity.  We're pleased to see that the software we started using just two months ago is mostly working.  For more of the details, our event page is here.

 So far, 14 people reported feeling this earthquake.  Actually, 9, because 5 reported feeling intensity I, which is no shaking.  No harm no foul.