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

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.

Seismogram with two clear and obvious large events. The smaller one appears to happen after the larger one and there are a handful of event smaller events happening between the two.

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.

Topographic map showing the location of the event by labeling it with a red circle. The map shows the event occurring west of Mt.Venus.

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