Volcano activity of September 11, 2012 - Strong seismicity at Little Sitkin (Alaska) + activity other volcanoes worldwide

This (almost) daily post intends to follow up the activity changes of volcanoes all over the world.
This post is written by geologist Richard Wilson who specializes in Volcano seismicity and Armand Vervaeck. Please feel free to tell us about new or changed activity if we haven't written about it. -

September 11, 2012 volcano activity

A little more volcanic activity (mostly internal) to report today.

In Alaska, Little Sitkin volcano continues to rumble with earthquakes (mostly hidden in the noise caused by passage of an Aleutian low pressure system). (station LSSA)

Update : A significant burst of seismicity has just begun at Little Sitkin volcano.  I have a strong feeling that this volcano intends to erupt!

Image courtesy Alaska Volcano Observatory


Seismogram just before writing the update

A seismic station located near Mount Martin also shows increased seismicity in the Katmai volcanoes over the past day (not pictured).

A swarm of volcano-tectonic earthquakes appears underway at Popocatepetl volcano (Mexico). The local earthquake there yesterday (at very top of record) was a magnitude M1.3, not as I poorly guessed, an M3.0. The repeating signatures after 2230 UTC are due to technical issues, not on-going seismicity.

Another outburst is visible on seismograms at Fuego volcano (Guatemala) (station FG3) this morning, while seismograms recorded at nearby Santa Maria show continuous, strong degassing tremor and occasional explosions (station STG6).

In El Salvador, San Miguel volcano seems to be building to another seismic crescendo (station VSM). This somewhat "normal" behaviour for the volcano usually takes place over a period of several weeks to months time. Seismicity builds from low levels to nearly continuous strong tremor, often interspersed with felt events near its culmination. Little surface activity occurs in conjunction with each crisis, other than small, intra-crater rockfalls and increased outgassing. The volcano then slowly (again, weeks to months) returns to its relatively docile state.

Nicaraguan volcanoes, Telica (station TELN), San Cristobal (station CRIN) and Apoyeque (station APYN) all show little change in behavior from the past few days with volcanic earthquakes and tremor at the former two vents and apparent tiny, repeating earthquakes at Apoyeque. Note the apparent increase in low-level tremor at San Cristobal following a regional earthquake, suggestive of continued internal instability at the volcano.

Things appear to be quieting at our two Colombian "regular performer" volcanoes, Nevado Del Ruiz (station OLLZ) and Galeras, while Machin volcano (station CIMA) seems to be picking up the slack with a second burst of earthquakes in as many days. And just as things appeared to be calming down at Sotara (station SOSO) volcano, it has rejuvenated with another earthquake swarm overnight. Neither of the latter volcanoes has experienced historical activity.

Volcanic earthquakes and low-level tremor are visible on seismograms at Tungurahua volcano (Ecuador (station RETU) today, despite technical difficulties with webicorders there.

Continuous volcanic tremor plagues White Island (New Zealand) again today and small local earthquakes and perhaps low level tremor (or wind?) are visible on seismograms at Ruapehu (station fwvz).

Seismicity at El Hierro is increasing strongly today and is up and down the last couple of weeks.

Lava flows did arrive in the proximity of a few villages on the slopes of Karangetang volcano, Indonesia. All inhabitants have been evacuated to safer locations.

Activity observed by satellites
Recent satellite imagery show SO2 plume activity remains strong at Nevado Del Ruiz, Kilauea (HI) and Sakurajima (Japan) volcanoes over the past few days.