“Failed” eruptions revealed by pattern classification analysis of gas emission and volcanic tremor data at Mt. Etna, Italy

by S. Falsaperla, B. Behncke, H. Langer, M. Neri, G. Salerno, S. Giammanco, E. Pecora, E. Biale

(Submitted to International Journal of Earth Sciences, August 2013)

Table 1

Chronology of episodes of seismic unrest* from 21 February to 20 April 2007 (all times are UT)

Date / Time/Surface Observations / Tremor / SOM/Fuzzy Clustering
1-2 March / 2030 (1 Mar) SOM colours green, cluster ID changes from ‘1’ to ‘2’
2325 (1 Mar) cluster ‘3’(SOM colours remain green)
0155 end of regime with cluster ‘3’(at 0200 there is cluster ‘2’ and at 0205 again cluster ‘3’)
0210 stable regime with cluster ‘2’
1640 return to cluster ‘1’
29 March** / 05:15 heat emission (satellite)
05:25 sustained lava fountaining
0615 weak ash emission continues
0645 tephra emission ceases
0700 paroxysm over / 0440 slight increase of spectral amplitudes
0525 increase of RMS amplitudes
0645 decrease of spectral and RMS amplitudes / 0430 SOM colours change, cluster ID changes from ‘1’ to ‘2’
0520 SOM colours purple – violet, cluster ‘3' ‘3’
0630 end of regime with cluster ‘3’, SOM colours green and blue
29-30 March / 2225 (29 Mar) SOM colours violet, cluster ID changes from ‘1’ to ‘2’
2315 (29 Mar) cluster ‘2’, SOM colours green changing to red-purple from 0045 on
0125 SOM colours purple and cluster ‘3’
0245 return to cluster ‘2’ and to SOM colours switching to green from 0330
0435 cluster ‘1’
30-31 March / 0545 (30 March) stable regime with cluster ‘2’and SOM colours green, gradually changing to violet from 1645
1835 (30 March) SOM colours yellow-orange and cluster ‘3’
2250 (30 March) SOM colours green, stable regime of cluster ‘2’
0120 cluster ID from ‘2’ to ‘1’, temporary mix of SOM colours blue-green followed by blue
31 March / 0705 cluster ‘2’, SOM colours prevalently violet
1040 SOM colours purple and cluster ‘3’
1120 return to SOM colours violet and to cluster ‘2’
1520 cluster ‘1’, SOM colours blue
1 April / 0655 cluster ‘2’, SOM colours change from blue-green to violet
0825 cluster ‘3’, SOM colours violet
0845 SOM colours change from violet to green, cluster ‘2’
1105 SOM colours change from green to blue, cluster ‘1’ prevailing; temporary switches to cluster ‘2’
2105 cluster ‘2’ prevailing, SOM colours green,
2200 cluster ‘3’ (one green triangle) associated with a teleseism
2205 SOM colours from green to blue-violet with temporary changes of cluster ID ‘1’ and ‘2’
2 April / 0400 cluster ‘1’, SOM colours change from blue to green
0645 SOM colours violet, cluster ‘2’
0810 SOM colours purple, cluster ‘3’ (three not adjacent triangles)
0840 cluster ‘2’, SOM colours gradually change from violet to green
1020 SOM colours switch from green to blue, cluster ID flips between ‘1’ and ‘2’, with cluster ‘1’ prevailing
4 April / 0150-0220 SOM colours green and cluster ‘2’ followed by cluster ‘1’
0245 SOM colours violet, cluster ‘2’
0255 SOM colours green, cluster ‘1’
0415 rapid development to purple SOM colours, cluster ‘2’
0525 cluster ‘3’, violet SOM colours prevailing
0705 stable regime of cluster ‘2’, SOM colours green
8 April / 0000 cluster ‘2’ starts suddenly, SOM colours change from violet to purple
0210 cluster ‘3’, SOM colours purple
0330 cluster ‘2’, gradual return to SOM colours violet
0405 cluster ‘1’, SOM colours blue
10-11 April** / 2318 (10 April) thermal anomaly (satellite)
0000-0100 activity increases, lava fountaining
0045 formation of tephra plume
0100-0200 strongest activity, fissure opens on S flank
0420 diminution of eruptive activity
0530 paroxysm over / 2330 (10 April)-0430 increase of spectral and RMS tremor amplitude
0420 general diminution of amplitudes / 2250 (10 April) SOM colours change from blue to purple – violet, and cluster ID from ‘1’ to ‘2’
0000–0420 cluster ‘3’ prevails, SOM colours purple-reddish
0500 return to SOM colours blue and to cluster ‘1’
12 April / 0735 SOM colours change from blue-green to purple, and cluster ID from ‘1’ to ‘2’
1225 cluster ‘3’ (one brown triangle)
1230 cluster ‘2’, SOM colours purple
1415 cluster ‘1’ prevailing, SOM colours change from green to blue
19 Apr / 05:20 degassing at SEC with weak thermal anomaly (videocamera) / 0340 cluster ‘2’, SOM colours violet-purple
0440 cluster ‘3’, SOM colours purple
0550 cluster ‘2’, SOM colours change from purple to green from 0710
0630 cluster ‘3’(one single purple triangle) followed by two green triangles at 1000-1005
1505 cluster ‘1’, SOM colours change from green to blue

* List of all the episodes where cluster #3 showed up in pattern classification

** Descriptions from Langer et al. (2011)

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