Alaska’s Redoubt volcano bears watching of late, but then it’s always been one to keep an eye on, as it is the most active Holocene stratovolcano in the Cook Inlet. On AVO’s seismographs it appears as the most seismically active volcano on their web page, but then there are over 90 volcanoes in the Aleutians and only a few of them are instrumented. Nevertheless Redoubt stands out in the data available to us for obvious reasons shown below.
Here we see quite a bit of seismic activity, including many A type events and quakes on August 28th and 29th. On the 30th there appeared a B type event, also known as a long period event, or tornill0 at 2310 hours or 11:10 pm on the seismograph time scale.
This was the only one I’ve seen recently, but I’ll be watching for more of them as they are significant seismic signatures detailed in my previous entry to this blog, and they were key in predicting a past eruption of Redoubt in late December of 1989 just in time to save lives at a local oil storage terminal.
Bernard Chouet had seen the long period events begin to appear on the seismographs, slowly increasing in frequency, and then rapidly increasing until the eruption that followed.
Workers there were very reluctant to leave as the oil would freeze up in the pipelines and cost millions per day in lost revenue, but they were finally convinced to leave. It took them two hours to shut down the operation and get everyone out, and just two hours after that Redoubt blew up sending a huge lahar down the valley, burying the oil storage terminal in three feet of mud. It could have easily been a lot worse.
Redoubt erupted again in March of 2009, shown here after having been seismically tempestuous for the preceding two months, and I think we might be seeing that coming again soon, especially if we see more of the long period events showing up. Redoubt does not directly threaten civilian populations but could pose a hazard for air traffic.
Just an aside here, yesterday, (August 30) there was a 6.8 magnitude quake under the Banda Sea, which is ringed to the east by a string of volcanoes, and just southwest of the epicenter of that quake is Gunungapi Wetar, an andacitic youngster just starting out life as a volcano and poking it’s cute little cone timidly above the waves there.
I shall be very interested to see if the recent seismic activity gives rise to any volcanic activity, especially with Gunungapi Wetar, which is only 16 miles or so from the quake epicenter and immediately north of a major undersea faultline. There’s not much at all on the web about this young volcano, but I’m rooting for this little guy to show us something. It last erupted in 1699, over 300 years ago, but this latest big quake might just kick it into action.