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. -
November 5, 2012 volcano activity
Rodger is back among us for some time. Here is his today’s report :
The volcanoes along the west coast of the Americas have become relatively tranquil since I was last home. Exceptions include: Mammoth Mountain volcano, CA (where small deep low-frequency events continue at a much reduced rate from last week’s swarm), Popocatepetl volcano, Mexico (where exhalations of gas and ash now occur at an average of 3 times per hour) and Nevado Del Ruiz volcano, Colombia (where volcano-tectonic seismicity has been elevated) and, across the pond at White Island volcano, New Zealand (where strong, sustained volcanic tremor continues).Popocateptl volcano burst, Mexico
The volcano-seismicity at Mammoth Mountain closely followed the M7.7 Haida Gwaii earthquake and it is possible that the activity may have been “energized” by the large Canadian event. Also, the Mammoth Mountain deep low-frequency earthquake swarm was followed a day later by several similar events further west beneath the central Sierra Nevada at unusual depths around 40 km. This westward progression of deep low-frequency event has been observed to the north beneath the Lake Tahoe region (and northwest of Truckee) and has been linked to westward encroachment of slow-slip into the Sierra Nevada along a detachment believed to exist beneath the Basin and Range geologic province. Definitely scientifically interesting activity! Activity at Popocatepetl appears to be part of the normal ebb and flow of activity there. The seismicity at Nevado Del Ruiz is more problematic. Does it represent renewed magma injection at the volcano, or is part of the volcano’s “cooling-down period” following eruptions which occurred there through this past summer? I have included seismograms from the onset of the most recent seismic episode to illustrate the unstable behavior of this volcano. (station OLLZ) Volcanic tremor at White Island continues a slow, but noticeable increase. In-step with heating of the volcanic system there. All we can do is watch and wait to see if the volcano intends on erupting or not. Low-level volcanic tremor has appeared on seismic records at Ruapehu volcano during the last month and tiny, intermittent earthquakes still affect Tongariro volcano which awakened this past summer. Recent satellite images show an assortment of sizes of SO2 plumes issuing from Popocatepetl, Nevado Del Ruiz, Nyiragongo (DRC) and Sakurajima (Japan) volcanoes. A large SO2 anomaly over Veniaminof volcano (Alaska Peninsula) is either a result of entrainment and concentration of anthropogenic SO2 by a weather system, or an artifact of data processing.
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