Concurrent Eruptions at Etna, Stromboli, and Vulcano

4 Concurrent eruptions

(1) (2) (1) 7 Andrea Billi , Emily E. Brodsky , and Renato Funiciello 8 (1) 9 Dipartimento di Scienze Geologiche, Università “Roma Tre”, Rome, Italy (2) 10 Department of Earth Sciences, University of California, Santa Cruz, CA, USA 11 12 13 14 15 16 17 Correspondence:

18 Andrea Billi 19 20 Dipartimento di Scienze Geologiche, 21 Università “Roma Tre” 22 Largo S. L. Murialdo, 1 23 00146, Rome, Italy 24 Tel: +39 0654888016 25 Fax: +39 0654888201 26 Email: [email protected] 27 28

29 Abstract

30 Anecdotes of concurrent eruptions at the Southern Italian volcanoes have persisted for more than

31 2000 years. Here we perform a statistical analysis of the eruption catalog to find that concurrent

32 eruptions among Etna, Stromboli, and Vulcano are much more frequent than would be expected by

33 chance. Based on the frequency of eruptions at each individual volcano, we calculate the expected

34 occurrence rate of concurrent eruptions and compare it to the observed rate. We find that pairs of

35 simultaneous eruptions occur as much as about 13 times more often than expected and triple

36 eruptions occur as much as 26 times more often. All of these concurrencies are statistically

37 significant at the 99% level.

40 Keywords: Etna, Stromboli, Vulcano, eruption, and volcano

41 1. Introduction

42 Interactions between large earthquakes and volcanic systems have excited a great deal of interest

43 in recent years [1-8]. Eruptions triggering other eruptions have been speculated about since at least

44 the 1st Century BC (e.g. Diodorus Siculus in Bibliotheca Historica), but recent systematic studies

45 have been rare [9, 10].

46 Southern Italy’s abundant volcanoes (Fig. 1) and long historical records make it ideal for the

47 study of concurrent eruptions. A link between Mt Etna and the Aeolian volcanoes was suggested by

48 Diodorus Siculus (in Bibliotheca Historica, 1st Century BC) and Julius Solinus (in Collectanea

49 Rerum Memorabilium, 4th Century AD) wrote that there should have been subterranean conduits

50 that linked and fed these volcanoes. de Dolomieu [11] hypothesized direct feeding relationships

51 between Etna and the Aeolian volcanoes, whereas Mercalli [12] supposed an indirect physical (i.e.

52 dynamic) link between these volcanoes.

53 Statistical evidence for a link between Etna, Stromboli, and Vulcano (Fig. 1) is addressed in this

54 paper. Our aim is to determine whether concurrent activity at these three volcanoes occurs at

55 significantly higher frequencies than expected based on the background rate. We will approach this

56 problem in three different ways. We will first do a statistical study of the cataloged eruptions using

57 a bootstrap probability method. The statistical method has the advantage of being quantitative, but

58 the disadvantage of providing little insight into the plethora of behavior that can fall under the

59 heading of eruption. In order to provide more qualitative information, we will go on to describe in

60 detail the activity during a few anecdotal instances of simultaneous eruptions. We finally discuss a

61 negative observation that rules out the role of large earthquakes in producing the concurrency.

63 2. Volcanic setting and activity

64 Mt Etna and the Aeolian Islands (Fig. 1) are located along the active destructive plate boundary

65 between Africa and Eurasia in the central Mediterranean region. In this tectonic framework, the

66 Aeolian volcanoes form an alkaline island arc whose activity started about 1.3 Myr ago and is still

67 active on at least three of the seven major islands, namely Lipari (last eruption in 729), Vulcano

68 (last eruptions in 1888-1892), and Stromboli. Hydrothermal activity offshore Panarea has occurred

69 in historical times and in recent years [13]. Stromboli is characterized by a persistent volcanic

70 activity consisting in continuous small explosions occurring at approximately regular intervals of a

71 few minutes (i.e. strombolian activity); however, individual events, such as lava effusions and

72 paroxysmal eruptions, are recorded at Stromboli during recent and historical times [14, 15]. The

73 volcanic activity of Vulcano has been characterized by powerful and impressive explosions (i.e.

74 vulcanian eruptions) alternated with less frequent effusive events [15, 16].

75 Volcanism in the Etnean area started about 0.5 Myr ago with tholeiitic magmas. The modern

76 volcano formed by a succession of volcanic edifices consisting in alternating pyroclastic and

77 effusive rocks [17]. The volcanic activity of Etna is, in fact, mostly effusive; however, explosive

78 activity has often occurred at the summit craters [18]. Lateral effusive and mildly explosive

79 eruptions have also been frequent at Mt Etna [19]. The source of Etna magmatism is possibly

80 connected with a mantle plume that Montelli et alii [20] imaged above 1000 km using seismic

81 tomography.

83 3. Concurrent eruptions

84 In this paper, we investigate the frequency of simultaneous eruptions. As eruptions are often

85 ongoing sequences with poorly defined start dates, we do not study the start of the eruptions. The

86 problem studied here is whether or not multiple ongoing eruptions overlap more often than expected

87 by chance.

88 We can construct a null hypothesis by using the observed record to calculate the expected rate of

89 concurrent eruptions if the volcanoes do not interact. If the probability of volcano A erupting in any

90 given month pA and the probability of volcano B erupting is pB and the two volcanoes are unlinked,

91 statistically independent systems, then the probability of a concurrent eruption pAB is the product

92 pApB. In this paper, we evaluate the null hypothesis that eruptions at each of the volcanoes are

93 statistically independent by calculating pApB from time-randomized catalogs and comparing it to the

94 observed frequency of concurrent eruptions.

95 Before evaluating the probabilities, we first limit the catalogs to provide uniform completeness

96 over the study interval. The catalogs are expected to be complete for the largest, most easily

97 observable eruptions, but progressively more incomplete at the smaller sizes. Volcanic eruptions

98 generally follow a power law distribution in sizes with many more small eruptions than large ones

99 as quantified by the Volcano Explosivity Index, VEI [21]. Significant depressions at small VEI

100 relative to the trend at large VEI suggest that there are missing eruptions in the catalog. This method

101 is similar to the standard comparison with the Gutenberg-Richter distribution used to determine the

102 magnitude at which seismic catalogs are complete [22]. Fig. 2 shows that the volcanic catalog used

103 for this region [15] is only complete for VEI ≥ 2. This rule is equally valid for eruptions in the 0-

104 1993, 1300-1500, 1500-1993, 1800-1993, and 1800-1900 periods of time (Fig. 2). For this reason,

105 we only use eruptions with VEI ≥ 2 for the analysis. The same threshold has been used previously

106 for global studies of eruption triggering [9].

107 We use the resulting catalog to estimate the probability of eruption per month and per year of

108 each individual volcano (i.e. Etna, Stromboli, and Vulcano) assuming statistical independence. The

109 simplest estimate of the probability of eruption is the number of time periods with eruptions divided

110 by the total number of time periods studied. The sampling bias of the limited catalog will

111 undoubtedly lead to errors in this estimate. These errors are evaluated using the standard bootstrap

112 method [23], which resamples the data set randomly in order to empirically capture probability

113 distribution (Table 1). Reported error bars are 1 standard deviation on 5000 bootstrap trials. The

114 advantage of bootstrapping is that no probability distribution needs to be assumed. The observed

115 data set is taken as a sampling of the true distribution and, therefore, the distribution of the

116 probability of occurrence is inferred from multiple samplings of the observations [23].

117 The next step is to multiply the individual probabilities to predict the probability of a concurrent

118 eruption if the systems are independent. This null hypothesis is evaluated by comparing the

119 observed frequency of concurrent eruptions to the predicted probabilities (Table 1). In the table, the

120 expected probability is the product of the independently inferred probabilities, e.g. pApB, and the

121 observed probability is the actual fraction of time periods containing concurrent eruptions. Every

122 pair of volcanoes erupts more frequently than would be expected based on the individual rates.

123 Stromboli and Vulcano are more closely correlated to each other than either is to the more distant

124 Mt Etna (Table 1). The most convincing correlation comes from the occurrence rate of triple

125 eruptions, this rate being more than 20 times as often than expected from individual eruptions rates

126 (Table 1). We again used bootstrapping to calculate the significance of the result. We time-

127 randomized each volcano catalog separately and then used a bootstrap method to determine the

128 probability distribution of concurrent eruptions in the time-randomized catalogs. We then compared

129 the observed rate of concurrency to the derived empirical probability distribution function and

130 found that the observation would occur by chance less than 0.5% of the time in all cases. Therefore,

131 the null hypothesis can be rejected at the 99.5% confidence level.

132 We limit our analysis to time periods of a month and longer because the exact dates are often

133 poorly constrained in the historical catalog. Nonetheless, it is interesting to investigate whether the

134 eruptions often occur in a particular order. During the 1700-1993 period, for which the eruption

135 dates are more reliable than those of the previous centuries [15], the order of eruption is often

136 Vulcano, Etna, and then Stromboli (Table 2). If only two of the three erupt, the order is often

137 preserved.

138 In order to check whether the statistical analysis is sensitive to the time window used to identify

139 concurrent eruptions, we repeated the analysis for year-long windows (Table 1b). Results from both

140 windows are consistent, which suggests that the result of statistically significant concurrent

141 eruptions is independent of the time scale used. Shorter time windows are not investigated because

142 the start of an eruptive episode often lasts weeks and thus concurrency on a time scale much less

143 than a month is poorly defined.

144

145 4. Examples of concurrent eruptions

146 The statistical evidence suggests a correlation between Southern Italian volcanoes; however

147 volcano catalogs are notoriously subjective. Eruptive activity is gradational and activity during a

148 given month may mean a variety of different phenomenon. To fill out this story, we therefore

149 provide narratives of four of the most notable examples of concurrent activity. Two of these

150 episodes fall outside our statistical study period and three involve observations from other Aeolian

151 volcanoes, but we include these stories anyhow to provide examples of the type of phenomena

152 expected.

153

154 4.1. Concurrent activity during 2002-2003

155 The 2002 eruption of Etna started the night between 26 and 27 October 2002 from the summit

156 craters, concurrently with the formation of ground-surface fractures in this area. From the summit

157 craters, fractures propagated toward the south and toward the northeast. Newly generated vents and

158 cones developed along these fractures. For about two months since the onset of the eruption,

159 voluminous emissions of ash occurred. Volcanic ashes fell in the nearby regions of Sicily and

160 Calabria. After about 95 days of almost continuous eruption, on 29 January 2003, Etna ceased most

161 of its effusive and explosive activity. The 2002-2003 eruption of Etna was highly explosive,

162 possibly one of the most explosive of the last 350 years (VEI ≥ 3 [24]).

163 Early in the morning of 3 November 2002, local fishermen observed spots of anomalous

164 seawater boiling and high mortality of fishes offshore Panarea, and perceived smell of sulfurs. In

165 particular, five major sites of gas emissions were found around the islets of Lisca Bianca, Bottaro,

166 and Lisca Nera. At these sites, ascent of gas bubbles with diameter up to 1 m on the sea surface

167 signaled the presence of submarine gas-emissions. With the exception of one site close to Lisca

168 Bianca, these sites were previously unknown as gas-emitting spots. Gas emissions originated from

169 NW- and NE-striking fractures in volcanic rocks lying at depths between 8 and 30 m from the sea

170 surface [25]. Gas emissions offshore Panarea gradually ceased during the first months of 2003 [26].

171 On 28 December 2002, after 17 years of mild although continuous volcanic activity, an intense

172 eruption began at Stromboli. The eruption was preceded by seismic swarms and by an increase in

173 volcanic tremors since 3 November 2002, concurrently with the onset of gas emissions offshore

174 Panarea. Since 28 December 2002, lava flowed from the Stromboli summit crater into the sea along

175 the steep northwest flank. Renewed lava flow occurred since 30 December 2002. The eruption

176 mostly ceased by 5 April 2003, when a powerful explosion occurred at the summit crater of

177 Stromboli [27].

178

179 4.2. Concurrent activity during 1886-1890

180 From 10 January to 31 March 1886, strombolian activity occurred at Vulcano. On 22 January

181 1886, volcanic explosions occurred at Stromboli. On 18 May 1886, an eruption began at the summit

182 craters of Mt Etna [28]. This eruption was highly explosive (VEI = 3).

183 During January, March, and November 1887, volcanic explosions occurred at Stromboli. On 3

184 August 1888, an eruption began at Vulcano. The eruptive activity of Vulcano ceased in March

185 1990. The 1888-1890 eruption of Vulcano was highly explosive (VEI = 3). On 23 October 1888,

186 volcanic explosions and lava fountains occurred at Stromboli. On 29 November 1888, offshore

187 Vulcano, local fishermen observed boiling seawater and associated fish mortality, and perceived

188 smell of sulfurs [28-30].

189

190 4.3. Concurrent activity during 1865

191 On 30 January 1865, an explosive (VEI ≥ 2) eruption occurred at Etna [31, 32]. At the onset of

192 the eruption, NE-striking fractures propagated across the summit crater of Mt Etna. Several vents

193 and cones formed along these fractures. The effusive and explosive activity at Mt Etna lasted for

194 about 90 days. Voluminous emissions of ash, which fell for about two months in the nearby regions

195 of Sicily and Calabria, accompanied the eruption from the beginning. During the 1865 eruption of

196 Etna, emissions of sulfurous gases occurred offshore Panarea. From 26 January to 2 February 1865,

197 volcanic explosions occurred at Stromboli [30].

198

199 4.4. Concurrent activity during 126 BC

200 Paulus Orosius, a Latin historian lived in the 5th Century, in his Historiarum Adversus Paganos

201 wrote: “Under the consulate of M. Aemilius Laepidus and L. Orestes, Mt Etna was violently shaken

202 by a powerful tremble and poured out waves of fire globes. The day after, the Lipari Islands (i.e.

203 also known as Aeolian Islands) and nearby the sea reached such a high boiling point that rocks were

204 burnt and broken up. Ships, axes, and wax were carbonized and melted, dead fishes were burnt on

205 the sea surface, and several men, except those who were able to escape, were stifled and their inner

206 organs burnt by breathing”. Strabo, a Greek geographer, and Julius Obsequens, a Latin historian,

207 had reported the same event in documents dated back to the 1st Century BC (Geographia) and to the

208 4th Century (De Prodigiis), respectively. The events reported by the above-cited authors refer to the

209 explosive eruption of Mt Etna started in June 126 BC and to the contemporaneous emissions of gas

210 occurred in the offshore area between Vulcano and Panarea [15].

211

212 5. Large earthquakes as triggers?

213 An advantage of studying this region is that there exists an extensive pre-instrumental seismic

214 record. The historical chronicles [15, 33] report six large earthquakes (epicentral MCS intensity ≥

215 IX-X and magnitude possibly ≥ 6.5) in the eastern Sicily (Fig. 1) during historical times. (1) The 4

216 February 1169 earthquake, which hit the eastern Sicily and western Calabria. The epicentral MCS

217 intensity for this event is XI. An eruption from the southern flank of Mt Etna is doubtfully dated

218 back to February 1169. (2) The 10 December 1542 earthquake, which hit the southeastern Sicily

219 with epicentral MCS intensity of IX-X. No concurrent volcanic and seismic phenomena are

220 documented for the Etnean and Aeolian areas. (3) The 11 January 1693 earthquake, which hit the

221 southeastern Sicily with epicentral MCS intensity of XI. No concurrent volcanic and seismic

222 phenomena are reported for the Etnean and Aeolian areas except for a doubtful eruption at Mt Etna

223 dated back to 9 January 1693. (4) The 5 March 1823 earthquake, which hit the Patti Gulf along the

224 northeastern coast of Sicily. The maximum MCS intensity recorded is X. No concurrent volcanic

225 and seismic phenomena are reported for the Etnean and Aeolian areas. (5) The 28 December 1908

226 earthquake, which hit the Messina Straits and the surrounding region. The maximum MCS intensity

227 recorded is XI. No concurrent volcanic and seismic phenomena are reported for the Etnean and

228 Aeolian areas. (6) The 15 October 1911 earthquake, which hit the southeastern flank of Mt Etna.

229 The NNW-SSE-elongated epicentral area was characterized by a maximum MCS intensity of X.

230 The earthquake was preceded by an eruption occurred between 10 and 22 September 1911 from the

231 northeastern flank of Mt Etna. This eruption was contemporaneous with an intense seismic activity

232 at Stromboli.

233 Notably, there is no evidence – anecdotal or otherwise – that either local or remote large

234 earthquakes triggered eruptions in the region (see the NEIC Catalog available on-line at

235 http://neic.usgs.gov/neis/epic/ and the INGV Catalog available on-line at http://www.ingv.it/).

236

237 6. Discussion

238 Pairs of simultaneous eruptions occur between about 6 and 13 times more often than expected

239 from the separate rates of each system when analyzed per month, and between about 4 and 6 times

240 more often when analyzed per year (Table 1). Triple eruptions occur about 21 times more often than

241 expected if the systems were independent, when analyzed per month and 26 times more often when

242 analyzed per year. Although the exact value of the increased occurrence depends on the timescale,

243 in all cases the results are statistically significant at the 99.5% level, indicating that concurrency is a

244 robust observation independent of the time scale used (i.e. months and years).

245 The statistics make it clear that there is a significant correlation between volcanoes in the

246 recorded catalog. The key issue in interpreting the results is determining how accurately the catalog

247 reflects the true state of the eruptions. We have partially addressed this issue by limiting the study to

248 mid-sized explosive eruptions (VEI ≥ 2), which are unlikely to be missed in a densely populated

249 region and appear to be complete according to a test of the size distribution (Fig. 2). Another

250 important issue is the treatment of ongoing eruptions. Here we exclusively study the overlap time of

251 eruptions rather than trying to pinpoint the eruption start. We also do not attempt to distinguish

252 between eruptive styles or locations within a given volcanic system. This leaves the eruptive

253 triggers poorly constrained, but makes the statistics possible for the historical data.

254 A final, and potentially fatal, problem is reporting bias. After an eruption, observers are more

255 likely to make note of activity on other area volcanoes. This is less likely a problem late in recent

256 years and the VEI distribution suggests that at least most large eruptions (VEI ≥ 2) are recorded.

257 However, it is possible that the concurrence statistics are simply reflecting a trend in the reporting.

258 In that case, the apparent concurrency can be used as a tool to highlight catalog errors. However,

259 given the anecdotal evidence, we think that it is more likely that the signal is real. The hypothesis of

260 reporting bias is untestable in retrospect, but can be easily tested in the future as eruptions continue

261 to develop. We look forward to our predictions of a high incidence of concurrent eruptions being

262 confirmed (or refuted) with the passage of time.

263 The above-discussed statistical and anecdotal evidence indicate links in the activity of Etna,

264 Stromboli, and Vulcano, but the data do not allow an unequivocal identification of a plausible

265 triggering mechanism. Some constraints on the triggering mechanisms can, however, be derived

266 from our results. Previous studies on earthquake-eruption and eruption-eruption triggering

267 mechanisms [10] established that eruptions and volcanic unrest could be triggered by earthquakes

268 through static stresses (i.e. the fault slip induces a permanent deformation in the crust) or dynamic

269 stresses (i.e. transient stresses induced by the passage of seismic waves). The same reasoning can be

270 applied to eruption-eruption triggering [34]. Either the static stress generated by the movement of

271 magma or the shaking generated by the eruptions themselves can trigger adjacent volcanoes. The

272 lack of eruption triggering from the larger earthquakes in the region argues that the eruption-related

273 earthquakes themselves are not the main agent of coupling. More prolonged dynamic stresses

274 generated through eruptive processes would be a more viable candidate [34]. We speculate that

275 since Vulcano is often the most explosive of the volcanoes, it likely generates the strongest seismic

276 waves and hence usually begins the sequence. Of course, whether or not a given input successfully

277 triggers an eruption depends on the state of the volcano. We do not expect to observe perfect

278 correlations or a deterministic sequence of eruptions.

279 Alternatively, the concurrent eruptions may be responding to a common, external stimulus. The

280 “superswarm” of earthquakes and eruptions could be a result of either: (1) a dynamic stress from

281 strong, remote earthquakes, or (2) a tectonic stress associated with the N-S convergence between

282 Africa and Eurasia. Although the possibility of remotely triggered eruptions cannot be generally

283 ruled out, this mechanism did not probably activate the concurrent eruptions discussed in this paper

284 because no remote strong earthquakes are known to be chronologically near (i.e. within hours or

285 days) to these phenomena. Both seismological and geodetic evidences show that a N-S tectonic

286 compression is active in the northeastern Sicily [35-37]. Such stress may be periodically relieved by

287 a large earthquake on one segment of the regional fault network [38] or, more often, by

288 superswarms consisting in eruptions and low-magnitude earthquakes where the triggering threshold

289 is low (i.e. in the active volcanic districts). The model of a tectonic stress stimulating occasional

290 “superswarms” in the volcanic districts of Southern Italy revives Mercalli’s [12] original idea of

291 “dynamic relationships” between Etna and the Aeolian volcanoes, and of a “dependence of these

292 volcanoes on the same fracture system”. Mercalli, in fact, claimed that the nature of the

293 relationships between these volcanoes should not have been magmatological [11] but physical and

294 external to them.

295

296 7. Concluding remarks

297 The analysis of data presented in this paper demonstrates the statistical significance of temporal

298 correlations between reported volcanic phenomena at Etna, Stromboli, and Vulcano. The statistical

299 evidence here provided for coupled phenomena compels further research to better constrain the

300 temporal pattern of such phenomena and to identify their causes. The identification of volcanic

301 precursors is fundamental to mitigate the relative hazard in densely populated areas such as the

302 Aeolian Islands and Mt Etna. An integrated monitoring system, including measurements of

303 deformation, seismicity, and gas flux, may significantly help in revealing the causes for coupled

304 volcanic phenomena at Etna and Aeolian Islands in the next years.

305 The apparent causal relationships between seismic and volcanic phenomena in regions

306 characterized by low-magnitude earthquakes are still mostly unexplained. One of the models (i.e.

307 “superswarms”) proposed in this paper for explaining the concurrent phenomena at Etna, Stromboli,

308 and Vulcano may be a suitable one for other regions where volcanism and seismicity are nearly

309 concurrent but the earthquakes are low in magnitude.

310 The importance of the statistical analyses presented in this paper consists in the fact that,

311 whereas earthquakes and eruptions triggered by large earthquakes are increasingly being well

312 documented [1, 7], except a few studies [6, 9, 10], quantitative analyses of concurrent eruptions at

313 adjacent volcanoes are poorly documented. Because of the long historical records, Southern Italy is

314 the only place in the world where interactions between active volcanoes can be analyzed over about

315 the last two millennia.

316

317

318 Acknowledgments. We thank F. Barberi and D. Peacock for suggestions on an early version of

319 the manuscript, C. Cimarelli for Fig. 1, L. Da Riva for helping in Latin translations. Financial 320 support to AB comes from a GNDT project coordinated by L. Beranzoli with the help of P. Favali 321 and C. Faccenna. C. Jaupart and two anonymous reviewers are thanked for their comments.

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16 Stromboli N ds lan n Is eolia Panarea Filicudi A Salina Alicudi Lipari Vulcano Tyrrhenian Sea Patti Gulf

Sicily Calabria

Messina Straits Mt Etna Italy 42°20'N Ionian Sea 50 km

Figure 1. Hillshade of the northeastern Sicily (Southern Italy), including the Aeolian Islands and Mt Etna. = 0-1993 AD 1000 = 1300-1500 AD = 1500-1993 AD = 1800-1993 AD 100 = 1800-1900 AD

1 Number of eruptions = VEI 01234 Volcanic Explosivity Index (VEI)

Figure 2. Relationship between the number of eruptions and the "magnitude" of the eruption, which is characterized by the Volcanic Explosivity Index (VEI [21]). Data are from the Simkin and Siebert's Catalog [15]. and pertain to the three considered volcanoes, i.e. Etna, Stromboli, and Vulcano. Historical eruptions are divided into four groups corresponding to the following periods: 0-1993, 1300-1500, 1500-1993, 1800-1993 and 1800-1900 AD. Assuming that the distribution of the eruption sizes roughly follows a power-law, we infer that the catalog of eruptions is statistically complete and meaningful for eruptions with VEI >= 2.

Table 1. Observed and expected compound probabilities for the occurrence of (a) months and (b) years including eruptions at two or three volcanoes among Etna, Stromboli, and Vulcano during 0-1993 AD. The relative data are from [15] and are listed in Tables SM1 and SM2 in the Supplementary Material.

(a) volcanoes compound probability (%) observed expected Etna-Stromboli 0.19 0.027 ± 0.0027 Etna-Vulcano 0.28 0.045 ± 0.0036 Stromboli-Vulcano 0.042 0.0033 ± 0.00042 Etna-Stromboli-Vulcano 0.0042 0.00020 ± 0.000026

(b) volcanoes compound probability (%) observed expected Etna-Stromboli 1.6 0.25 ± 0.037 Etna-Vulcano 0.50 0.14 ± 0.027 Stromboli-Vulcano 0.25 0.042 ± 0.0093 Etna-Stromboli-Vulcano 0.10 0.0038 ± 0.00086

Table 2. Time order of erupting volcanoes in the occasion of duple and triple concurrent eruptions between 1700 and 1993. Data are from [15]. type of erupting no. of times in which the volcano concurrent volcanoes erupted before the others in the eruptions occasion of concurrent eruptions Etna Stromboli Vulcano duple Etna-Stromboli 23 3 / duple Etna-Vulcano 0 / 4 duple Stromboli-Vulcano / 0 2 triple Etna-Stromboli-Vulcano 0 0 1

Table SM1. Eruption (with VEI ≥ 2) occurrences by month between 0 and 1993 AD at Etna, Stromboli, and Vulcano. VEI = Volcanic Explosivity Index [21]; 0 = no occurrence; 1 = occurrence. Data are from the Simkin and Siebert’s Catalog [15].

Etna Stromboli Vulcano year month eruptions VEI eruptions VEI eruptions VEI 252 2 1 3 0 0 1329 6 1 2 0 0 1329 7 1 3 0 0 1329 8 1 3 0 0 1381 8 1 2 0 0 1408 11 1 3 0 0 1444 2 0 0 1 3 1536 3 1 3 0 0 1536 4 1 3 0 0 1537 3 1 2 0 0 1537 4 1 2 0 0 1537 5 1 2 0 0 1537 6 1 2 0 0 1537 7 1 2 0 0 1541 7 1 2 0 0 1566 11 1 2 0 0 1603 7 1 2 0 0 1603 8 1 2 0 0 1603 9 1 2 0 0 1603 10 1 2 0 0 1603 11 1 2 0 0 1603 12 1 2 0 0 1604 1 1 2 0 0 1604 2 1 2 0 0 1604 3 1 2 0 0 1604 4 1 2 0 0 1604 5 1 2 0 0 1604 6 1 2 0 0 1604 7 1 2 0 0 1604 8 1 2 0 0 1604 9 1 2 0 0 1604 10 1 2 0 0 1604 11 1 2 0 0 1604 12 1 2 0 0 1605 1 1 2 0 0 1605 2 1 2 0 0 1605 3 1 2 0 0 1605 4 1 2 0 0 1605 5 1 2 0 0 1605 6 1 2 0 0 1605 7 1 2 0 0 1605 8 1 2 0 0 1605 9 1 2 0 0 1605 10 1 2 0 0 1605 11 1 2 0 0 1605 12 1 2 0 0 1606 1 1 2 0 0 1606 2 1 2 0 0 1606 3 1 2 0 0 1606 4 1 2 0 0 1606 5 1 2 0 0 1606 6 1 2 0 0 1606 7 1 2 0 0 1606 8 1 2 0 0 1606 9 1 2 0 0 1606 10 1 2 0 0 1606 11 1 2 0 0 1606 12 1 2 0 0 1607 1 1 2 0 0 1607 2 1 2 0 0 1607 3 1 2 0 0 1607 4 1 2 0 0 1607 5 1 2 0 0 1607 6 1 2 0 0 1607 7 1 2 0 0 1607 8 1 2 0 0 1607 9 1 2 0 0

1 1607 10 1 2 0 0 1607 11 1 2 0 0 1607 12 1 2 0 0 1608 1 1 2 0 0 1608 2 1 2 0 0 1608 3 1 2 0 0 1608 4 1 2 0 0 1608 5 1 2 0 0 1608 6 1 2 0 0 1608 7 1 2 0 0 1608 8 1 2 0 0 1608 9 1 2 0 0 1608 10 1 2 0 0 1608 11 1 2 0 0 1608 12 1 2 0 0 1609 1 1 2 0 0 1609 2 1 2 0 0 1609 3 1 2 0 0 1609 4 1 2 0 0 1609 5 1 2 0 0 1609 6 1 2 0 0 1609 7 1 2 0 0 1609 8 1 2 0 0 1609 9 1 2 0 0 1609 10 1 2 0 0 1609 11 1 2 0 0 1609 12 1 2 0 0 1610 1 1 2 0 0 1610 2 1 2 0 0 1610 3 1 2 0 0 1610 4 1 2 0 0 1610 5 1 2 0 0 1610 6 1 2 0 0 1610 7 1 2 0 0 1610 8 1 2 0 0 1614 7 1 2 0 0 1614 8 1 2 0 0 1614 9 1 2 0 0 1614 10 1 2 0 0 1614 11 1 2 0 0 1614 12 1 2 0 0 1615 1 1 2 0 0 1615 2 1 2 0 0 1615 3 1 2 0 0 1615 4 1 2 0 0 1615 5 1 2 0 0 1615 6 1 2 0 0 1615 7 1 2 0 0 1615 8 1 2 0 0 1615 9 1 2 0 0 1615 10 1 2 0 0 1615 11 1 2 0 0 1615 12 1 2 0 0 1616 1 1 2 0 0 1616 2 1 2 0 0 1616 3 1 2 0 0 1616 4 1 2 0 0 1616 5 1 2 0 0 1616 6 1 2 0 0 1616 7 1 2 0 0 1616 8 1 2 0 0 1616 9 1 2 0 0 1616 10 1 2 0 0 1616 11 1 2 0 0 1616 12 1 2 0 0 1617 1 1 2 0 0 1617 2 1 2 0 0 1617 3 1 2 0 0 1617 4 1 2 0 0 1617 5 1 2 0 0 1617 6 1 2 0 0 1617 7 1 2 0 0 1617 8 1 2 0 0 1617 9 1 2 0 0 1617 10 1 2 0 0 1617 11 1 2 0 0 1617 12 1 2 0 0

2 1618 1 1 2 0 0 1618 2 1 2 0 0 1618 3 1 2 0 0 1618 4 1 2 0 0 1618 5 1 2 0 0 1618 6 1 2 0 0 1618 7 1 2 0 0 1618 8 1 2 0 0 1618 9 1 2 0 0 1618 10 1 2 0 0 1618 11 1 2 0 0 1618 12 1 2 0 0 1619 1 1 2 0 0 1619 2 1 2 0 0 1619 3 1 2 0 0 1619 4 1 2 0 0 1619 5 1 2 0 0 1619 6 1 2 0 0 1619 7 1 2 0 0 1619 8 1 2 0 0 1619 9 1 2 0 0 1619 10 1 2 0 0 1619 11 1 2 0 0 1619 12 1 2 0 0 1620 1 1 2 0 0 1620 2 1 2 0 0 1620 3 1 2 0 0 1620 4 1 2 0 0 1620 5 1 2 0 0 1620 6 1 2 0 0 1620 7 1 2 0 0 1620 8 1 2 0 0 1620 9 1 2 0 0 1620 10 1 2 0 0 1620 11 1 2 0 0 1620 12 1 2 0 0 1621 1 1 2 0 0 1621 2 1 2 0 0 1621 3 1 2 0 0 1621 4 1 2 0 0 1621 5 1 2 0 0 1621 6 1 2 0 0 1621 7 1 2 0 0 1621 8 1 2 0 0 1621 9 1 2 0 0 1621 10 1 2 0 0 1621 11 1 2 0 0 1621 12 1 2 0 0 1622 1 1 2 0 0 1622 2 1 2 0 0 1622 3 1 2 0 0 1622 4 1 2 0 0 1622 5 1 2 0 0 1622 6 1 2 0 0 1622 7 1 2 0 0 1622 8 1 2 0 0 1622 9 1 2 0 0 1622 10 1 2 0 0 1622 11 1 2 0 0 1622 12 1 2 0 0 1623 1 1 2 0 0 1623 2 1 2 0 0 1623 3 1 2 0 0 1623 4 1 2 0 0 1623 5 1 2 0 0 1623 6 1 2 0 0 1623 7 1 2 0 0 1623 8 1 2 0 0 1623 9 1 2 0 0 1623 10 1 2 0 0 1623 11 1 2 0 0 1623 12 1 2 0 0 1624 1 1 2 0 0 1626 3 0 0 1 3 1626 4 0 0 1 3 1646 11 1 2 0 0 1646 12 1 2 0 0

3 1647 1 1 2 0 0 1647 2 1 2 0 0 1647 3 1 2 0 0 1647 4 1 2 0 0 1647 5 1 2 0 0 1647 6 1 2 0 0 1647 7 1 2 0 0 1647 8 1 2 0 0 1647 9 1 2 0 0 1647 10 1 2 0 0 1647 11 1 2 0 0 1669 3 1 3 0 0 1669 4 1 3 0 0 1669 5 1 3 0 0 1669 6 1 3 0 0 1669 7 1 3 0 0 1682 9 1 2 0 0 1693 12 1 3 0 0 1694 1 1 3 0 0 1694 2 1 3 0 0 1694 3 1 3 0 0 1694 4 1 3 0 0 1694 5 1 3 0 0 1694 6 1 3 0 0 1694 7 1 3 0 0 1694 8 1 3 0 0 1694 9 1 3 0 0 1694 10 1 3 0 0 1694 11 1 3 0 0 1723 11 1 2 0 0 1723 12 1 2 0 0 1724 1 1 2 0 0 1724 2 1 2 0 0 1724 3 1 2 0 0 1724 4 1 2 0 0 1724 5 1 2 0 0 1731 12 0 0 1 3 1732 1 0 0 1 3 1732 2 0 0 1 3 1732 3 0 0 1 3 1732 4 0 0 1 3 1732 5 0 0 1 3 1732 6 0 0 1 3 1732 7 0 0 1 3 1732 8 0 0 1 3 1732 9 0 0 1 3 1732 10 0 0 1 3 1732 11 0 0 1 3 1732 12 1 2 0 1 3 1733 1 1 2 0 1 3 1733 2 0 0 1 3 1733 3 0 0 1 3 1733 4 0 0 1 3 1733 5 0 0 1 3 1733 6 0 0 1 3 1733 7 0 0 1 3 1733 8 0 0 1 3 1733 9 0 0 1 3 1733 10 0 0 1 3 1733 11 0 0 1 3 1733 12 0 0 1 3 1734 1 0 0 1 3 1734 2 0 0 1 3 1734 3 0 0 1 3 1734 4 0 0 1 3 1734 5 0 0 1 3 1734 6 0 0 1 3 1734 7 0 0 1 3 1734 8 0 0 1 3 1734 9 0 0 1 3 1734 10 0 0 1 3 1734 11 0 0 1 3 1734 12 0 0 1 3 1735 1 0 0 1 3 1735 2 0 0 1 3 1735 3 0 0 1 3 1735 4 0 0 1 3

4 1735 5 0 0 1 3 1735 6 0 0 1 3 1735 7 0 0 1 3 1735 8 0 0 1 3 1735 9 0 0 1 3 1735 10 1 2 0 1 3 1735 11 1 2 0 1 3 1735 12 1 2 0 1 3 1736 1 1 2 0 1 3 1736 2 1 2 0 1 3 1736 3 1 2 0 1 3 1736 4 1 2 0 1 3 1736 5 1 2 0 1 3 1736 6 1 2 0 1 3 1736 7 1 2 0 1 3 1736 8 1 2 0 1 3 1736 9 1 2 0 1 3 1736 10 0 0 1 3 1736 11 0 0 1 3 1736 12 0 0 1 3 1737 1 0 0 1 3 1737 2 0 0 1 3 1737 3 0 0 1 3 1737 4 0 0 1 3 1737 5 0 0 1 3 1737 6 0 0 1 3 1737 7 0 0 1 3 1737 8 0 0 1 3 1737 9 0 0 1 3 1737 10 0 0 1 3 1737 11 0 0 1 3 1737 12 0 0 1 3 1738 1 0 0 1 3 1738 2 0 0 1 3 1738 3 0 0 1 3 1738 4 0 0 1 3 1738 5 0 0 1 3 1738 6 0 0 1 3 1738 7 0 0 1 3 1738 8 0 0 1 3 1738 9 0 0 1 3 1738 10 0 0 1 3 1738 11 0 0 1 3 1738 12 0 0 1 3 1739 1 0 0 1 3 1744 7 1 2 0 0 1744 8 1 2 0 0 1744 9 1 2 0 0 1744 10 1 2 0 0 1744 11 1 2 0 0 1744 12 1 2 0 0 1745 1 1 2 0 0 1745 2 1 2 0 0 1745 3 1 2 0 0 1745 4 1 2 0 0 1745 5 1 2 0 0 1745 6 1 2 0 0 1745 7 1 2 0 0 1745 8 1 2 0 0 1745 9 1 2 0 0 1747 9 1 2 0 0 1747 10 1 2 0 0 1747 11 1 2 0 0 1747 12 1 2 0 0 1748 1 1 2 0 0 1748 2 1 2 0 0 1748 3 1 2 0 0 1748 4 1 2 0 0 1748 5 1 2 0 0 1748 6 1 2 0 0 1748 7 1 2 0 0 1748 8 1 2 0 0 1748 9 1 2 0 0 1748 10 1 2 0 0 1748 11 1 2 0 0 1748 12 1 2 0 0 1749 1 1 2 0 0

5 1749 2 1 2 0 0 1749 3 1 2 0 0 1752 12 1 2 0 0 1753 1 1 2 0 0 1753 2 1 2 0 0 1753 3 1 2 0 0 1753 4 1 2 0 0 1753 5 1 2 0 0 1753 6 1 2 0 0 1753 7 1 2 0 0 1753 8 1 2 0 0 1753 9 1 2 0 0 1753 10 1 2 0 0 1753 11 1 2 0 0 1753 12 1 2 0 0 1754 1 1 2 0 0 1754 2 1 2 0 0 1754 3 1 2 0 0 1754 4 1 2 0 0 1754 5 1 2 0 0 1754 6 1 2 0 0 1754 7 1 2 0 0 1754 8 1 2 0 0 1754 9 1 2 0 0 1754 10 1 2 0 0 1754 11 1 2 0 0 1754 12 1 2 0 0 1755 1 1 2 0 0 1755 2 1 2 0 0 1755 3 1 2 0 0 1755 4 1 2 0 0 1755 5 1 2 0 0 1755 6 1 2 0 0 1755 7 1 2 0 0 1755 8 1 2 0 0 1755 9 1 2 0 0 1755 10 1 2 0 0 1755 11 1 2 0 0 1755 12 1 2 0 0 1756 1 1 2 0 0 1756 2 1 2 0 0 1756 3 1 2 0 0 1756 4 1 2 0 0 1756 5 1 2 0 0 1756 6 1 2 0 0 1756 7 1 2 0 0 1756 8 1 2 0 0 1756 9 1 2 0 0 1756 10 1 2 0 0 1756 11 1 2 0 0 1756 12 1 2 0 0 1757 1 1 2 0 0 1757 2 1 2 0 0 1757 3 1 2 0 0 1757 4 1 2 0 0 1757 5 1 2 0 0 1757 6 1 2 0 0 1757 7 1 2 0 0 1757 8 1 2 0 0 1757 9 1 2 0 0 1757 10 1 2 0 0 1757 11 1 2 0 0 1757 12 1 2 0 0 1758 1 1 2 0 0 1758 11 1 2 0 0 1758 12 1 2 0 0 1759 1 1 2 0 0 1759 2 1 2 0 0 1763 2 1 2 0 0 1763 3 1 2 0 0 1763 6 1 3 0 0 1763 7 1 3 0 0 1763 8 1 3 0 0 1763 9 1 3 0 0 1766 4 1 2 0 0 1766 5 1 2 0 0 1766 6 1 2 0 0

6 1766 7 1 2 0 0 1766 8 1 2 0 0 1766 9 1 2 0 0 1766 10 1 2 0 0 1766 11 1 2 0 0 1771 2 0 0 1 3 1771 3 0 0 1 3 1771 4 0 0 1 3 1771 5 0 0 1 3 1778 3 0 1 2 0 1780 4 1 2 0 0 1780 5 1 2 0 0 1780 6 1 2 0 0 1781 3 1 2 0 0 1781 4 1 2 0 0 1781 5 1 2 0 0 1787 6 1 4 0 0 1787 7 1 4 0 0 1787 8 1 4 0 0 1791 2 1 2 0 0 1791 3 1 2 0 0 1791 4 1 2 0 0 1791 5 1 2 0 0 1791 6 1 2 0 0 1791 7 1 2 0 0 1791 8 1 2 0 0 1791 9 1 2 0 0 1792 3 1 2 0 0 1792 4 1 2 0 0 1792 5 1 3 0 0 1792 6 1 3 0 0 1792 7 1 3 0 0 1792 8 1 3 0 0 1792 9 1 3 0 0 1792 10 1 3 0 0 1792 11 1 3 0 0 1792 12 1 3 0 0 1793 1 1 3 0 0 1793 2 1 3 0 0 1793 3 1 3 0 0 1793 4 1 3 0 0 1793 5 1 3 0 0 1797 12 1 2 0 0 1798 1 1 2 0 0 1798 2 1 2 0 0 1798 3 1 2 0 0 1798 4 1 2 0 0 1798 5 1 2 0 0 1798 6 1 2 0 0 1798 7 1 2 0 0 1798 8 1 2 0 0 1798 9 1 2 0 0 1798 10 1 2 0 0 1798 11 1 2 0 0 1798 12 1 2 0 0 1799 1 1 2 0 0 1799 2 1 2 0 0 1799 3 1 2 0 0 1799 4 1 2 0 0 1799 5 1 2 0 0 1799 6 1 2 0 0 1799 7 1 2 0 0 1799 8 1 2 0 0 1799 9 1 2 0 0 1799 10 1 2 0 0 1799 11 1 2 0 0 1799 12 1 2 0 0 1800 1 1 2 0 0 1800 2 1 2 0 0 1800 3 1 2 0 0 1800 4 1 2 0 0 1800 5 1 2 0 0 1800 6 1 2 0 0 1800 7 1 2 0 0 1800 8 1 2 0 0 1800 9 1 2 0 0 1800 10 1 2 0 0

7 1800 11 1 2 0 0 1800 12 1 2 0 0 1801 1 1 2 0 0 1802 11 1 2 0 0 1803 12 1 2 0 0 1804 1 1 2 0 0 1804 2 1 2 0 0 1804 3 1 2 0 0 1804 4 1 2 0 0 1804 5 1 2 0 0 1804 6 1 2 0 0 1804 7 1 2 0 0 1804 8 1 2 0 0 1804 9 1 2 0 0 1804 10 1 2 0 0 1804 11 1 2 0 0 1804 12 1 2 0 0 1805 1 1 2 0 0 1805 2 1 2 0 0 1805 3 1 2 0 0 1805 4 1 2 0 0 1805 5 1 2 0 0 1805 6 1 2 0 0 1805 7 1 2 0 0 1805 8 1 2 0 0 1805 9 1 2 0 0 1805 10 1 2 0 0 1805 11 1 2 0 0 1805 12 1 2 0 0 1806 1 1 2 0 0 1806 2 1 2 0 0 1806 3 1 2 0 0 1806 4 1 2 0 0 1806 5 1 2 0 0 1806 6 1 2 0 0 1806 7 1 2 0 0 1806 8 1 2 0 0 1806 9 1 2 0 0 1806 10 1 2 0 0 1806 11 1 2 0 0 1806 12 1 2 0 0 1807 1 1 2 0 0 1807 2 1 2 0 0 1807 3 1 2 0 0 1807 4 1 2 0 0 1807 5 1 2 0 0 1807 6 1 2 0 0 1807 7 1 2 0 0 1807 8 1 2 0 0 1807 9 1 2 0 0 1807 10 1 2 0 0 1807 11 1 2 0 0 1807 12 1 2 0 0 1808 1 1 2 0 0 1808 2 1 2 0 0 1808 3 1 2 0 0 1808 4 1 2 0 0 1808 5 1 2 0 0 1808 6 1 2 0 0 1808 7 1 2 0 0 1808 8 1 2 0 0 1808 9 1 2 0 0 1808 10 1 2 0 0 1808 11 1 2 0 0 1808 12 1 2 0 0 1809 1 1 2 0 0 1809 2 1 2 0 0 1809 3 1 2 0 0 1809 4 1 2 0 0 1809 5 1 2 0 0 1809 6 1 2 0 0 1809 7 1 2 0 0 1809 8 1 2 0 0 1809 9 1 2 0 0 1809 10 1 2 0 0 1809 11 1 2 0 0 1811 10 1 2 0 0

8 1811 11 1 2 0 0 1811 12 1 2 0 0 1812 1 1 2 0 0 1812 2 1 2 0 0 1812 3 1 2 0 0 1812 4 1 2 0 0 1812 5 1 2 0 0 1819 5 1 3 0 0 1819 6 1 3 0 0 1819 7 1 3 0 0 1819 8 1 3 0 0 1822 10 0 1 3 0 1828 8 1 2 0 0 1828 9 1 2 0 0 1828 10 1 2 0 0 1828 11 1 2 0 0 1828 12 1 2 0 0 1829 1 1 2 0 0 1829 2 1 2 0 0 1829 3 1 2 0 0 1829 4 1 2 0 0 1829 5 1 2 0 0 1829 6 1 2 0 0 1829 7 1 2 0 0 1829 8 1 2 0 0 1829 9 1 2 0 0 1829 10 1 2 0 0 1829 11 1 2 0 0 1829 12 1 2 0 0 1830 1 1 2 0 0 1830 2 1 2 0 0 1830 3 1 2 0 0 1830 4 1 2 0 0 1830 5 1 2 0 0 1830 6 1 2 0 0 1830 7 1 2 0 0 1830 8 1 2 0 0 1830 9 1 2 0 0 1830 10 1 2 0 0 1830 11 1 2 0 0 1830 12 1 2 0 0 1831 1 1 2 0 0 1831 2 1 2 0 0 1831 3 1 2 0 0 1831 4 1 2 0 0 1831 5 1 2 0 0 1831 6 1 2 0 0 1831 7 1 2 0 0 1831 8 1 2 0 0 1831 9 1 2 0 0 1831 10 1 2 0 0 1831 11 1 2 0 0 1831 12 1 2 0 0 1832 1 1 2 0 0 1832 2 1 2 0 0 1832 3 1 2 0 0 1832 4 1 2 0 0 1832 5 1 2 0 0 1832 6 1 2 0 0 1832 7 1 2 0 0 1832 8 1 2 0 0 1832 9 1 2 0 0 1832 10 1 2 0 0 1832 11 1 2 0 0 1833 3 1 2 0 0 1838 7 1 2 0 0 1838 8 1 2 0 0 1838 9 1 2 0 0 1838 10 1 2 0 0 1838 11 1 2 0 0 1838 12 1 2 0 0 1839 1 1 2 0 0 1839 2 1 2 0 0 1842 11 1 2 0 0 1842 12 1 2 0 0 1843 11 1 2 0 0 1852 8 1 2 0 0

9 1852 9 1 2 0 0 1852 10 1 2 0 0 1852 11 1 2 0 0 1852 12 1 2 0 0 1853 1 1 2 0 0 1853 2 1 2 0 0 1853 3 1 2 0 0 1853 4 1 2 0 0 1853 5 1 2 0 0 1855 10 0 1 2 0 1856 7 0 1 2 0 1863 5 1 2 0 0 1863 6 1 2 0 0 1863 7 1 2 0 0 1864 8 1 2 0 0 1864 9 1 2 0 0 1865 1 1 2 1 2 0 1865 2 1 2 1 2 0 1865 3 1 2 0 0 1865 4 1 2 0 0 1865 5 1 2 0 0 1865 6 1 2 0 0 1868 11 1 3 0 0 1868 12 1 3 0 0 1873 9 0 0 1 3 1873 10 0 0 1 3 1873 11 0 0 1 3 1873 12 0 0 1 3 1874 1 0 0 1 3 1874 2 0 0 1 3 1874 3 0 0 1 3 1874 4 0 0 1 3 1874 5 1 2 0 1 3 1874 6 1 2 1 2 1 3 1874 7 1 2 0 1 3 1874 8 1 2 0 1 3 1874 9 0 0 1 3 1874 10 0 0 1 3 1874 11 0 0 1 3 1874 12 1 2 0 1 3 1875 1 1 2 0 1 3 1875 2 1 2 0 1 3 1875 3 1 2 0 1 3 1875 4 1 2 0 1 3 1875 5 1 2 0 1 3 1875 6 1 2 0 1 3 1875 7 1 2 0 1 3 1875 8 1 2 0 1 3 1875 9 1 2 0 1 3 1875 10 1 2 0 1 3 1875 11 1 2 0 1 3 1875 12 1 2 0 1 3 1876 1 1 2 0 1 3 1876 2 1 2 0 1 3 1876 3 1 2 0 1 3 1876 4 1 2 0 1 3 1876 5 1 2 0 1 3 1876 6 1 2 0 1 3 1876 7 1 2 0 1 3 1876 8 1 2 0 1 3 1876 9 1 2 0 1 3 1876 10 1 2 0 1 3 1876 11 1 2 0 1 3 1876 12 1 2 0 1 3 1877 1 1 2 0 1 3 1877 2 1 2 0 1 3 1877 3 1 2 0 1 3 1877 4 1 2 0 1 3 1877 5 1 2 0 1 3 1877 6 1 2 0 1 3 1877 7 1 2 0 1 3 1877 8 1 2 0 1 3 1877 9 1 2 0 1 3 1877 10 1 2 0 1 3 1877 11 1 2 0 1 3 1877 12 1 2 0 1 3 1878 1 1 2 0 1 3

10 1878 2 1 2 0 1 3 1878 3 1 2 0 1 3 1878 4 1 2 0 1 3 1878 5 1 2 0 1 3 1878 6 1 2 0 1 3 1878 7 1 2 0 1 3 1878 8 1 2 0 1 3 1878 9 1 2 0 1 3 1878 10 1 2 0 1 3 1878 11 1 2 0 1 3 1878 12 1 2 0 1 3 1879 1 1 2 0 1 3 1879 2 1 2 1 2 0 1879 3 1 2 0 0 1879 4 1 2 0 0 1879 5 1 3 0 0 1879 6 1 3 1 2 0 1879 7 1 2 0 0 1879 8 1 2 0 0 1879 9 1 2 0 0 1879 10 1 2 0 0 1879 11 1 2 0 0 1879 12 1 2 0 0 1880 1 1 2 0 0 1880 2 1 2 0 0 1880 3 1 2 0 0 1880 4 1 2 0 0 1880 5 1 2 0 0 1880 6 1 2 0 0 1880 7 1 2 0 0 1880 8 1 2 0 0 1880 9 1 2 0 0 1880 10 1 2 0 0 1880 11 1 2 0 0 1880 12 1 2 0 0 1881 1 1 2 0 0 1881 2 1 2 0 0 1881 3 1 2 0 0 1881 4 1 2 0 0 1881 5 1 2 0 0 1881 6 1 2 0 0 1881 7 1 2 0 0 1881 8 1 2 0 0 1881 9 1 2 0 0 1881 10 1 2 1 2 0 1881 11 1 2 0 0 1881 12 1 2 0 0 1882 1 1 2 0 0 1882 2 1 2 0 0 1882 3 1 2 0 0 1882 4 1 2 0 0 1882 5 1 2 0 0 1882 6 1 2 0 0 1882 7 1 2 0 0 1882 8 1 2 0 0 1882 9 1 2 0 0 1882 10 1 2 0 0 1882 11 1 2 1 3 0 1882 12 1 2 0 0 1883 1 1 2 0 0 1883 2 1 2 0 0 1883 3 1 2 0 0 1885 3 0 1 3 0 1886 1 0 0 1 3 1886 5 1 3 0 0 1886 6 1 3 0 0 1888 8 0 0 1 3 1888 9 0 0 1 3 1888 10 0 1 2 1 3 1888 11 0 1 2 1 3 1888 12 0 1 2 1 3 1889 1 0 1 2 1 3 1889 2 0 1 2 1 3 1889 3 0 1 2 1 3 1889 4 0 1 2 1 3 1889 5 0 1 2 1 3 1889 6 0 1 2 1 3

11 1889 7 0 0 1 3 1889 8 0 0 1 3 1889 9 0 0 1 3 1889 10 0 0 1 3 1889 11 0 0 1 3 1889 12 0 0 1 3 1890 1 0 0 1 3 1890 2 0 0 1 3 1890 3 0 0 1 3 1891 6 0 1 3 0 1891 7 0 1 3 0 1891 8 0 1 3 0 1892 7 1 2 0 0 1892 8 1 2 0 0 1892 9 1 2 0 0 1892 10 1 2 0 0 1892 11 1 2 1 2 0 1892 12 1 2 0 0 1893 1 0 1 2 0 1893 4 1 2 0 0 1893 5 1 2 0 0 1893 6 1 2 0 0 1893 7 1 2 0 0 1893 8 1 2 0 0 1893 9 1 2 0 0 1893 10 1 2 0 0 1893 11 1 2 1 2 0 1893 12 1 2 0 0 1894 1 1 2 0 0 1894 2 1 2 0 0 1894 3 1 2 0 0 1894 4 1 2 0 0 1894 5 1 2 0 0 1894 6 1 2 0 0 1894 7 1 2 0 0 1894 8 1 2 0 0 1894 9 1 2 0 0 1894 10 1 2 0 0 1894 11 1 2 0 0 1894 12 1 2 0 0 1895 1 1 2 0 0 1895 2 1 2 0 0 1895 3 1 2 1 2 0 1895 4 1 2 0 0 1895 5 1 2 0 0 1895 6 1 2 0 0 1895 7 1 2 0 0 1895 8 1 2 0 0 1895 9 1 2 0 0 1895 10 1 2 0 0 1895 11 1 2 0 0 1895 12 1 2 0 0 1896 1 1 2 0 0 1896 2 1 2 0 0 1896 3 1 2 0 0 1896 4 1 2 0 0 1896 5 1 2 0 0 1896 6 1 2 0 0 1896 7 1 2 1 2 0 1896 8 1 2 0 0 1896 9 1 2 0 0 1896 10 1 2 0 0 1896 11 1 2 0 0 1896 12 1 2 0 0 1897 1 1 2 0 0 1897 2 1 2 0 0 1897 3 1 2 0 0 1897 4 1 2 0 0 1897 5 1 2 0 0 1897 6 1 2 0 0 1897 7 1 2 1 2 0 1897 8 1 2 0 0 1897 9 1 2 0 0 1897 10 1 2 0 0 1897 11 1 2 0 0 1897 12 1 2 0 0 1898 1 1 2 0 0

12 1898 2 1 2 0 0 1898 3 1 2 0 0 1898 4 1 2 0 0 1898 5 1 2 0 0 1898 6 1 2 0 0 1898 8 0 1 2 0 1899 7 1 3 0 0 1899 8 1 3 0 0 1900 8 0 1 2 0 1900 10 0 1 2 0 1903 1 0 1 2 0 1903 2 0 1 2 0 1903 3 0 1 2 0 1903 4 0 1 2 0 1903 5 0 1 2 0 1903 6 0 1 2 0 1903 11 0 1 2 0 1905 4 0 1 2 0 1906 4 0 1 2 0 1906 7 0 1 2 0 1907 1 0 1 3 0 1907 2 0 1 3 0 1907 3 0 1 3 0 1907 4 0 1 3 0 1907 5 0 1 3 0 1908 4 1 2 0 0 1910 3 1 2 0 0 1910 4 1 2 0 0 1910 12 1 2 0 0 1911 1 1 2 0 0 1911 2 1 2 0 0 1912 7 0 1 2 0 1912 8 1 3 1 2 0 1913 11 1 2 0 0 1913 12 1 2 0 0 1914 1 1 2 0 0 1914 2 1 2 0 0 1914 3 1 2 0 0 1914 4 1 2 0 0 1914 5 1 2 0 0 1914 6 1 2 0 0 1914 7 1 2 0 0 1914 8 1 2 0 0 1914 9 1 2 0 0 1914 10 1 2 0 0 1914 11 1 2 0 0 1914 12 1 2 0 0 1915 1 1 2 0 0 1915 2 1 2 0 0 1915 3 1 2 0 0 1915 4 1 2 0 0 1915 5 1 2 0 0 1915 6 1 2 1 2 0 1915 7 1 2 1 2 0 1915 8 1 2 1 2 0 1915 9 1 2 1 2 0 1915 10 1 2 1 2 0 1915 11 1 2 1 2 0 1915 12 1 2 0 0 1916 1 1 2 0 0 1916 2 1 2 0 0 1916 3 1 2 0 0 1916 4 1 2 0 0 1916 5 1 2 0 0 1916 6 1 2 1 2 0 1916 7 1 2 1 2 0 1916 8 1 2 0 0 1916 9 1 2 0 0 1916 10 1 2 0 0 1916 11 1 2 0 0 1916 12 1 2 0 0 1917 1 1 2 0 0 1917 2 1 2 0 0 1917 3 1 2 0 0 1917 6 1 2 0 0 1917 7 1 2 0 0 1919 3 1 2 0 0

13 1919 4 1 2 0 0 1919 5 1 2 1 3 0 1919 6 1 2 0 0 1919 7 1 2 0 0 1919 8 1 2 0 0 1919 9 1 2 0 0 1919 10 1 2 0 0 1919 11 1 2 0 0 1919 12 1 2 0 0 1920 1 1 2 0 0 1920 2 1 2 0 0 1920 3 1 2 0 0 1920 4 1 2 0 0 1920 5 1 2 0 0 1920 6 1 2 0 0 1920 7 1 2 0 0 1920 8 1 2 0 0 1920 9 1 2 0 0 1920 10 1 2 0 0 1920 11 1 2 0 0 1920 12 1 2 0 0 1921 1 1 2 0 0 1921 2 1 2 0 0 1921 3 1 2 0 0 1921 4 1 2 0 0 1921 5 1 2 0 0 1921 6 1 2 1 2 0 1921 7 1 2 0 0 1921 8 1 2 0 0 1921 9 1 2 0 0 1921 10 1 2 0 0 1921 11 1 2 0 0 1921 12 1 2 0 0 1922 1 1 2 0 0 1922 2 1 2 0 0 1922 3 1 2 0 0 1922 4 1 2 0 0 1922 5 1 2 0 0 1922 6 1 2 0 0 1922 7 1 2 0 0 1922 8 1 2 0 0 1922 9 1 2 0 0 1922 10 1 2 0 0 1922 11 1 2 0 0 1922 12 1 2 0 0 1923 1 1 2 0 0 1923 2 1 2 0 0 1923 3 1 2 0 0 1923 4 1 2 0 0 1923 5 1 2 0 0 1923 6 1 2 0 0 1923 7 1 2 0 0 1930 2 0 1 2 0 1930 9 0 1 3 0 1930 10 0 1 3 0 1930 11 0 1 3 0 1930 12 0 1 3 0 1931 7 1 2 0 0 1931 8 1 2 0 0 1931 9 1 2 0 0 1931 10 1 2 0 0 1931 11 1 2 0 0 1931 12 1 2 0 0 1932 1 1 2 0 0 1932 2 1 2 0 0 1932 3 1 2 0 0 1932 4 1 2 0 0 1932 5 1 2 0 0 1932 6 1 2 0 0 1932 7 1 2 0 0 1932 8 1 2 0 0 1932 9 1 2 0 0 1932 10 1 2 0 0 1932 11 1 2 0 0 1932 12 1 2 0 0 1933 1 1 2 0 0 1933 2 1 2 0 0

14 1933 3 1 2 0 0 1933 4 1 2 0 0 1933 5 1 2 0 0 1933 6 1 2 0 0 1933 7 1 2 0 0 1933 8 1 2 0 0 1933 9 1 2 0 0 1934 2 0 1 2 0 1934 8 0 1 2 0 1935 7 1 2 0 0 1935 8 1 2 0 0 1935 9 1 2 0 0 1935 10 1 2 0 0 1935 11 1 2 0 0 1935 12 1 2 0 0 1936 1 1 2 1 2 0 1936 2 1 2 0 0 1936 3 1 2 0 0 1936 4 1 2 0 0 1936 5 1 2 0 0 1936 6 1 2 0 0 1936 7 1 2 0 0 1936 8 1 2 0 0 1936 9 1 2 0 0 1936 10 1 2 0 0 1936 11 1 2 0 0 1936 12 1 2 0 0 1937 1 1 2 1 2 0 1937 2 1 2 0 0 1937 3 1 2 0 0 1937 4 1 2 0 0 1937 5 1 2 0 0 1937 6 1 2 0 0 1937 7 1 2 0 0 1937 8 1 2 0 0 1937 9 1 2 0 0 1937 10 1 2 0 0 1937 11 1 2 1 2 0 1937 12 1 2 0 0 1938 1 1 2 0 0 1938 2 1 2 0 0 1938 3 1 2 0 0 1938 4 1 2 0 0 1938 5 1 2 0 0 1938 6 1 2 0 0 1938 7 1 2 0 0 1938 8 1 2 0 0 1938 9 1 2 0 0 1938 10 1 2 0 0 1938 11 1 2 1 2 0 1938 12 1 2 1 2 0 1939 1 1 2 1 2 0 1939 2 1 2 1 2 0 1939 3 1 2 1 2 0 1939 4 1 2 1 2 0 1939 5 1 2 1 2 0 1939 6 1 2 1 2 0 1939 7 1 2 0 0 1939 8 1 2 0 0 1939 9 1 2 0 0 1939 10 1 2 0 0 1939 11 1 2 0 0 1939 12 1 2 0 0 1940 3 1 3 0 0 1940 4 1 3 0 0 1940 5 1 3 0 0 1940 6 1 3 0 0 1940 7 1 3 0 0 1940 8 1 3 0 0 1940 9 1 3 0 0 1940 10 1 3 0 0 1940 11 1 3 0 0 1940 12 1 3 0 0 1941 1 1 3 0 0 1941 2 1 3 0 0 1941 3 1 3 0 0 1941 4 1 3 0 0

15 1941 5 1 3 0 0 1941 6 1 3 0 0 1941 7 1 3 0 0 1941 8 1 3 1 2 0 1941 9 1 3 0 0 1941 10 1 3 0 0 1941 11 1 3 0 0 1941 12 1 3 0 0 1942 1 1 3 0 0 1942 2 1 3 0 0 1942 3 1 3 0 0 1942 4 1 3 0 0 1942 5 1 3 0 0 1942 6 1 3 0 0 1942 7 1 2 0 0 1943 12 0 1 2 0 1944 1 0 1 2 0 1944 2 0 1 2 0 1944 8 0 1 2 0 1944 9 0 1 2 0 1944 10 0 1 2 0 1947 1 1 2 0 0 1947 2 1 2 0 0 1949 6 0 1 2 0 1949 12 1 2 0 0 1950 1 1 2 0 0 1950 10 0 1 2 0 1950 11 1 2 0 0 1950 12 1 2 0 0 1951 1 1 2 0 0 1951 2 1 2 0 0 1951 3 1 2 0 0 1951 4 1 2 1 2 0 1951 5 1 2 0 0 1951 6 1 2 0 0 1951 7 1 2 0 0 1951 8 1 2 0 0 1951 9 1 2 0 0 1951 10 1 2 0 0 1951 11 1 2 0 0 1951 12 1 2 0 0 1952 6 0 1 2 0 1953 7 1 2 0 0 1954 2 0 1 2 0 1954 3 0 1 2 0 1954 12 0 1 2 0 1955 1 0 1 2 0 1955 2 0 1 2 0 1955 3 0 1 2 0 1955 4 1 2 1 2 0 1955 5 1 2 1 2 0 1955 6 1 2 0 0 1955 7 1 2 0 0 1955 8 1 2 0 0 1955 9 1 2 0 0 1955 10 1 2 0 0 1955 11 1 2 0 0 1955 12 1 2 0 0 1956 1 1 2 0 0 1956 2 1 2 0 0 1956 3 1 2 0 0 1956 4 1 2 0 0 1957 2 1 2 0 0 1957 3 1 2 0 0 1957 4 1 2 0 0 1957 5 1 2 0 0 1957 8 1 2 0 0 1957 9 1 2 0 0 1957 10 1 2 0 0 1957 11 1 2 0 0 1957 12 1 2 0 0 1958 1 1 2 0 0 1958 2 1 2 0 0 1958 3 1 2 0 0 1958 4 1 2 0 0 1958 5 1 2 0 0 1959 5 0 1 2 0

16 1959 10 1 3 0 0 1959 11 1 3 0 0 1959 12 1 3 0 0 1960 1 1 3 0 0 1960 2 1 3 0 0 1960 3 1 3 0 0 1960 4 1 3 0 0 1960 5 1 3 0 0 1960 6 1 3 0 0 1960 7 1 3 0 0 1960 8 1 3 0 0 1960 9 1 3 0 0 1960 10 1 3 0 0 1960 11 1 3 0 0 1960 12 1 3 0 0 1961 1 1 3 0 0 1961 2 1 3 0 0 1961 3 1 3 0 0 1961 4 1 3 0 0 1961 5 1 3 0 0 1961 6 1 3 0 0 1961 7 1 3 0 0 1961 8 1 3 0 0 1961 9 1 3 0 0 1961 10 1 3 0 0 1961 11 1 3 0 0 1961 12 1 3 0 0 1962 1 1 3 0 0 1962 2 1 3 0 0 1962 3 1 3 0 0 1962 4 1 3 0 0 1962 5 1 3 0 0 1962 6 1 3 0 0 1962 7 1 3 0 0 1962 8 1 3 0 0 1962 9 1 3 0 0 1962 10 1 3 0 0 1962 11 1 3 0 0 1962 12 1 3 0 0 1963 1 1 3 0 0 1963 2 1 3 0 0 1963 3 1 3 0 0 1963 4 1 3 0 0 1963 5 1 3 0 0 1963 6 1 3 0 0 1963 7 1 3 0 0 1963 8 1 3 0 0 1963 9 1 3 0 0 1963 10 1 3 0 0 1963 11 1 3 0 0 1963 12 1 3 0 0 1964 1 1 3 0 0 1964 2 1 3 0 0 1964 3 1 3 0 0 1964 4 1 3 0 0 1964 5 1 3 0 0 1964 6 1 3 0 0 1964 7 1 3 0 0 1964 8 1 3 0 0 1964 9 1 3 0 0 1964 10 1 3 0 0 1964 11 1 3 0 0 1964 12 1 3 0 0 1966 1 1 2 0 0 1966 2 1 2 0 0 1966 3 1 2 0 0 1966 4 1 2 1 2 0 1966 5 1 2 0 0 1966 6 1 2 0 0 1966 7 1 2 0 0 1966 8 1 2 0 0 1966 9 1 2 0 0 1966 10 1 2 0 0 1966 11 1 2 0 0 1966 12 1 2 0 0 1967 1 1 2 0 0 1967 2 1 2 0 0

17 1967 3 1 2 0 0 1967 4 1 2 0 0 1967 5 1 2 0 0 1967 6 1 2 0 0 1967 7 1 2 0 0 1967 8 1 2 0 0 1967 9 1 2 0 0 1967 10 1 2 0 0 1967 11 1 2 0 0 1967 12 1 2 0 0 1968 1 1 2 0 0 1968 2 1 2 0 0 1968 3 1 2 0 0 1968 4 1 2 0 0 1968 5 1 2 0 0 1968 6 1 2 0 0 1968 7 1 2 0 0 1968 8 1 2 0 0 1968 9 1 2 0 0 1968 10 1 2 0 0 1968 11 1 2 0 0 1968 12 1 2 0 0 1969 1 1 2 0 0 1969 2 1 2 0 0 1969 3 1 2 0 0 1969 4 1 2 0 0 1969 5 1 2 0 0 1969 6 1 2 0 0 1969 7 1 2 0 0 1969 8 1 2 0 0 1969 9 1 2 0 0 1969 10 1 2 0 0 1969 11 1 2 0 0 1969 12 1 2 0 0 1970 1 1 2 0 0 1970 2 1 2 0 0 1970 3 1 2 0 0 1970 4 1 2 0 0 1970 5 1 2 0 0 1970 6 1 2 0 0 1970 7 1 2 0 0 1970 8 1 2 0 0 1970 9 1 2 0 0 1970 10 1 2 0 0 1970 11 1 2 0 0 1970 12 1 2 0 0 1971 1 1 2 0 0 1971 3 0 1 2 0 1971 4 1 2 1 2 0 1971 5 1 2 1 2 0 1971 6 1 2 0 0 1971 9 1 2 0 0 1971 10 1 2 0 0 1971 11 1 2 0 0 1971 12 1 2 0 0 1972 1 1 2 0 0 1972 2 1 2 0 0 1972 3 1 2 0 0 1972 4 1 2 0 0 1972 5 1 2 0 0 1972 6 1 2 0 0 1972 7 1 2 0 0 1972 8 1 2 0 0 1972 9 1 2 0 0 1972 10 1 2 0 0 1972 11 1 2 0 0 1972 12 1 2 0 0 1973 1 1 2 0 0 1973 2 1 2 0 0 1973 3 1 2 0 0 1973 4 1 2 0 0 1973 5 1 2 0 0 1973 6 1 2 0 0 1973 7 1 2 0 0 1973 8 1 2 0 0 1973 9 1 2 0 0 1973 10 1 2 0 0

18 1973 11 1 2 0 0 1973 12 1 2 0 0 1974 1 1 2 0 0 1974 2 1 2 0 0 1974 3 1 2 0 0 1974 4 1 2 0 0 1974 5 1 2 0 0 1974 6 1 2 0 0 1974 7 1 2 0 0 1974 8 1 2 0 0 1974 9 1 2 0 0 1974 10 1 2 0 0 1974 11 1 2 0 0 1974 12 1 2 0 0 1975 1 1 2 0 0 1975 2 1 2 0 0 1975 3 1 2 0 0 1975 4 1 2 0 0 1975 5 1 2 0 0 1975 6 1 2 0 0 1975 7 1 2 0 0 1975 8 1 2 0 0 1975 9 1 2 0 0 1975 10 1 2 0 0 1975 11 1 2 0 0 1975 12 1 2 0 0 1976 1 1 2 0 0 1976 2 1 2 0 0 1976 3 1 2 0 0 1976 4 1 2 0 0 1976 5 1 2 0 0 1976 6 1 2 0 0 1976 7 1 2 0 0 1976 8 1 2 0 0 1976 9 1 2 0 0 1976 10 1 2 0 0 1976 11 1 2 0 0 1976 12 1 2 0 0 1977 1 1 2 0 0 1977 2 1 2 0 0 1977 3 1 2 0 0 1977 4 1 2 0 0 1977 5 1 2 0 0 1977 6 1 2 0 0 1977 7 1 2 0 0 1977 8 1 2 0 0 1977 9 1 2 0 0 1977 10 1 2 0 0 1977 11 1 2 0 0 1977 12 1 2 0 0 1978 1 1 2 0 0 1978 2 1 2 0 0 1978 3 1 2 0 0 1978 4 1 2 0 0 1978 5 1 2 0 0 1978 6 1 2 0 0 1978 7 1 2 0 0 1978 8 1 2 0 0 1978 9 1 2 0 0 1978 10 1 2 0 0 1978 11 1 2 0 0 1978 12 1 2 0 0 1979 1 1 2 0 0 1979 2 1 2 0 0 1979 3 1 2 0 0 1979 7 1 2 0 0 1979 8 1 2 0 0 1979 9 1 2 0 0 1979 10 1 2 0 0 1979 11 1 2 0 0 1979 12 1 2 0 0 1980 1 1 2 0 0 1980 2 1 2 0 0 1980 3 1 2 0 0 1980 4 1 2 0 0 1980 5 1 2 0 0 1980 6 1 2 0 0

19 1980 7 1 3 0 0 1980 8 1 3 0 0 1980 9 1 3 0 0 1980 10 1 2 0 0 1980 11 1 2 0 0 1980 12 1 2 0 0 1981 1 1 2 0 0 1981 2 1 2 0 0 1981 3 1 2 0 0 1981 4 1 2 0 0 1981 5 1 2 0 0 1981 6 1 2 0 0 1981 7 1 2 0 0 1981 8 1 2 0 0 1981 9 1 2 0 0 1981 10 1 2 0 0 1981 11 1 2 0 0 1981 12 1 2 0 0 1982 1 1 2 0 0 1982 2 1 2 0 0 1982 3 1 2 0 0 1982 4 1 2 0 0 1982 5 1 2 0 0 1982 6 1 2 0 0 1982 7 1 2 0 0 1982 8 1 2 0 0 1982 9 1 2 0 0 1982 10 1 2 0 0 1982 11 1 2 0 0 1982 12 1 2 0 0 1983 1 1 2 0 0 1983 2 1 2 0 0 1983 3 1 2 0 0 1983 4 1 2 0 0 1983 5 1 2 0 0 1983 6 1 2 0 0 1983 7 1 2 0 0 1983 8 1 2 0 0 1983 9 1 2 0 0 1983 10 1 2 0 0 1983 11 1 2 0 0 1983 12 1 2 0 0 1984 1 1 2 0 0 1984 2 1 2 0 0 1984 3 1 2 0 0 1984 4 1 2 0 0 1984 5 1 2 0 0 1984 6 1 2 0 0 1984 7 1 2 0 0 1984 8 1 2 0 0 1984 9 1 2 0 0 1984 10 1 2 0 0 1984 11 1 2 0 0 1984 12 1 2 0 0 1985 1 1 2 0 0 1985 2 1 2 0 0 1985 3 1 2 0 0 1985 4 1 2 0 0 1985 5 1 2 0 0 1985 6 1 2 0 0 1985 7 1 2 0 0 1985 8 1 2 0 0 1985 9 1 2 0 0 1985 10 1 2 0 0 1985 11 1 2 0 0 1985 12 1 2 1 2 0 1986 1 1 2 1 2 0 1986 2 1 2 1 2 0 1986 3 1 2 1 2 0 1986 4 1 2 1 2 0 1986 5 1 2 0 0 1986 6 1 2 0 0 1986 7 1 2 0 0 1986 8 1 2 0 0 1986 9 1 2 0 0 1986 10 1 2 0 0 1986 11 1 2 0 0

20 1986 12 1 2 0 0 1987 1 1 2 0 0 1987 2 1 2 0 0 1987 3 1 2 0 0 1987 4 1 2 0 0 1987 5 1 2 0 0 1987 6 1 2 0 0 1987 7 1 2 0 0 1987 8 1 2 0 0 1987 9 1 2 0 0 1987 10 1 2 0 0 1987 11 1 2 0 0 1987 12 1 2 0 0 1988 1 1 2 0 0 1988 2 1 2 0 0 1988 3 1 2 0 0 1988 4 1 2 0 0 1988 5 1 2 0 0 1988 6 1 2 0 0 1988 7 1 2 0 0 1988 8 1 2 0 0 1988 9 1 2 0 0 1988 10 1 2 0 0 1988 11 1 2 0 0 1988 12 1 2 0 0 1989 1 1 2 0 0 1989 2 1 2 0 0 1989 3 1 2 0 0 1989 4 1 2 0 0 1989 5 1 2 0 0 1989 6 1 2 0 0 1989 7 1 2 0 0 1989 8 1 2 0 0 1989 9 1 2 0 0 1989 10 1 2 0 0 1989 11 1 2 0 0 1989 12 1 2 0 0 1990 1 1 2 0 0 1990 2 1 2 0 0 1990 3 1 2 0 0 1990 4 1 2 0 0 1990 5 1 2 0 0 1990 6 1 2 0 0 1990 7 1 2 0 0 1990 8 1 2 0 0 1990 9 1 2 0 0 1990 10 1 2 0 0 1990 11 1 2 0 0 1990 12 1 2 0 0 1991 1 1 2 0 0 1991 2 1 2 0 0 1991 3 1 2 0 0 1991 4 1 2 0 0 1991 5 1 2 0 0 1991 6 1 2 0 0 1991 7 1 2 0 0 1991 8 1 2 0 0 1991 9 1 2 0 0 1991 10 1 2 0 0 1991 11 1 2 0 0 1991 12 1 2 0 0 1992 1 1 2 0 0 1992 2 1 2 0 0 1992 3 1 2 0 0 1992 4 1 2 0 0 1992 5 1 2 0 0 1992 6 1 2 0 0 1992 7 1 2 0 0 1992 8 1 2 0 0 1992 9 1 2 0 0 1992 10 1 2 0 0 1992 11 1 2 0 0 1992 12 1 2 0 0 1993 1 1 2 0 0 1993 2 1 2 0 0 1993 3 1 2 0 0

21 Table SM2. Eruption (with VEI ≥ 2) occurrences by year between 0 and 1993 AD at Etna, Stromboli, and Vulcano. VEI = Volcanic Explosivity Index [21]; 0 = no occurrence; 1 = occurrence. Data are from the Simkin and Siebert’s Catalog [15].

Etna Stromboli Vulcano year eruptions VEI eruptions VEI eruptions VEI 252 1 3 0 0 526 0 0 1 3 925 0 0 1 3 1157 1 2 0 0 1160 1 2 0 0 1164 1 2 0 0 1194 1 2 0 0 1222 1 2 0 0 1250 1 2 0 0 1329 1 3 0 0 1333 1 2 0 0 1350 1 2 0 0 1381 1 2 0 0 1408 1 3 0 0 1444 1 2 0 1 3 1536 1 3 0 0 1537 1 2 0 0 1541 1 2 0 0 1550 0 0 1 3 1554 1 2 0 0 1558 0 1 2 0 1566 1 2 0 0 1595 1 3 0 0 1603 1 2 0 0 1607 1 2 0 0 1610 1 2 0 0 1614 1 2 0 0 1615 1 2 0 0 1616 1 2 0 0 1617 1 2 0 0 1618 1 2 0 0 1619 1 2 0 0 1620 1 2 0 0 1621 1 2 0 0 1622 1 2 0 0 1623 1 2 0 0 1624 1 2 0 0 1626 0 0 1 3 1646 1 2 0 0 1647 1 2 0 0 1669 1 3 0 0 1682 1 2 0 0 1693 1 3 0 0 1694 1 3 0 0 1723 1 2 0 0 1724 1 2 0 0 1727 0 0 1 3 1731 0 0 1 3 1732 1 2 0 1 3 1733 1 2 0 1 3 1734 0 0 1 3 1735 1 2 0 1 3 1736 1 2 0 1 3 1737 0 0 1 3 1738 0 0 1 3 1739 0 0 1 3 1744 1 2 0 0 1745 1 2 0 0 1747 1 2 0 0 1748 1 2 0 0 1749 1 2 0 0 1752 1 2 0 0 1753 1 2 0 0 1754 1 2 0 0 1755 1 2 0 0 1756 1 2 0 0 1757 1 2 0 0

1 1758 1 2 0 0 1759 1 2 0 0 1763 1 3 0 0 1766 1 2 0 0 1768 0 1 2 0 1770 0 1 2 0 1771 0 0 1 3 1778 0 1 2 0 1780 1 2 0 1 2 1781 1 2 0 0 1786 0 0 1 3 1787 1 4 0 0 1791 1 2 0 0 1792 1 3 0 0 1793 1 3 0 0 1797 1 2 0 0 1798 1 2 0 0 1799 1 2 0 0 1800 1 2 0 0 1801 1 2 0 0 1802 1 2 0 0 1803 1 2 0 0 1804 1 2 0 0 1805 1 2 0 0 1806 1 2 0 0 1807 1 2 0 0 1808 1 2 0 0 1809 1 2 0 0 1811 1 2 0 0 1812 1 2 0 0 1819 1 3 0 0 1822 0 1 3 1 2 1823 0 0 1 2 1828 1 2 0 0 1829 1 2 0 0 1830 1 2 0 0 1831 1 2 0 0 1832 1 2 0 0 1833 1 2 1 2 0 1838 1 2 0 0 1839 1 2 0 0 1842 1 2 0 0 1843 1 2 0 0 1850 0 1 2 0 1852 1 2 0 0 1853 1 2 0 0 1855 0 1 2 0 1856 0 1 2 0 1863 1 2 0 0 1864 1 2 0 0 1865 1 2 1 2 0 1868 1 3 0 0 1873 0 0 1 3 1874 1 2 1 2 1 3 1875 0 0 1 3 1876 0 0 1 3 1877 0 0 1 3 1878 1 2 0 1 3 1879 1 3 1 2 1 3 1880 1 2 0 0 1881 1 2 1 2 0 1882 1 2 1 3 0 1883 1 2 0 0 1885 0 1 2 0 1886 1 3 0 1 3 1888 0 1 2 1 3 1889 0 1 2 1 3 1890 0 0 1 3 1891 0 1 3 0 1892 1 2 1 2 0 1893 1 2 1 2 0 1894 1 2 0 0 1895 1 2 1 2 0 1896 1 2 1 2 0 1897 1 2 1 2 0 1898 1 2 1 2 0 1899 1 3 0 0

2 1900 0 1 2 0 1903 0 1 2 0 1905 0 1 2 0 1906 0 1 2 0 1907 0 1 3 0 1908 1 2 0 0 1910 1 2 0 0 1911 1 2 0 0 1912 1 3 1 2 0 1913 1 2 0 0 1914 1 2 0 0 1915 1 2 1 2 0 1916 1 2 1 2 0 1917 1 2 0 0 1919 1 2 1 3 0 1920 1 2 0 0 1921 1 2 1 2 0 1922 1 2 0 0 1923 1 2 0 0 1930 0 1 3 0 1931 1 2 0 0 1932 1 2 0 0 1933 1 2 0 0 1934 0 1 2 0 1935 1 2 0 0 1936 1 2 1 2 0 1937 1 2 1 2 0 1938 1 2 1 2 0 1939 1 2 1 2 0 1940 1 3 0 0 1941 1 3 1 2 0 1942 1 3 0 0 1943 0 1 2 0 1944 0 1 2 0 1947 1 2 0 0 1949 1 2 1 2 0 1950 1 2 1 2 0 1951 1 2 1 2 0 1952 0 1 2 0 1953 1 2 0 0 1954 0 1 2 0 1955 1 2 1 2 0 1956 1 2 0 0 1957 1 2 0 0 1958 1 2 0 0 1959 1 3 1 2 0 1960 1 3 0 0 1961 1 3 0 0 1962 1 3 0 0 1963 1 3 0 0 1964 1 3 0 0 1966 1 2 1 2 0 1967 1 2 0 0 1968 1 2 0 0 1969 1 2 0 0 1970 1 2 0 0 1971 1 2 1 2 0 1972 1 2 0 0 1973 1 2 0 0 1974 1 2 0 0 1975 1 2 0 0 1976 1 2 0 0 1977 1 2 0 0 1978 1 2 0 0 1979 1 2 0 0 1980 1 3 0 0 1981 1 2 0 0 1982 1 2 0 0 1983 1 2 0 0 1984 1 2 0 0 1985 1 2 1 2 0 1986 1 2 1 2 0 1987 1 2 0 0 1988 1 2 0 0 1989 1 2 0 0 1990 1 2 0 0 1991 1 2 0 0

3 1992 1 2 0 0 1993 1 2 0 0