On the cause of the 1908 Messina tsunami, southern Italy

Andrea Billi,1 Renato Funiciello,1 Liliana Minelli,1 Claudio Faccenna,1 Giancarlo Neri,2

Barbara Orecchio,2 and Debora Presti2

Received 15 January 2008; revised 13 February 2008; accepted 18 February 2008; published 19 March 2008.

[1] A century after the catastrophic event, the sources ofthe 1908 Messina, Southern Italy, earthquake and tsunami,which caused at least 60,000 deaths, remain uncertain.Through a simple backward ray-tracing method, we convertthe tsunami travel-time data reported in a 100-years-oldpaper into distances and find that the sources of theearthquake and tsunami are different. Overturning a long-held assumption, reconsideration of the available tsunami,bathymetric, seismic, and seismological data indicates thatthe tsunami was generated by an underwater landslide.Citation: Billi, A., R. Funiciello, L. Minelli, C. Faccenna, G. Neri,

B. Orecchio, and D. Presti (2008), On the cause of the 1908

Messina tsunami, southern Italy, Geophys. Res. Lett., 35, L06301,

doi:10.1029/2008GL033251.

1. Introduction

[2] As coastal settlements expand, locating and monitor-ing areas threatened by tsunami are concerns for local andinternational authorities responsible for mitigation of thishazard. On 28 December 1908, at 5.21 a.m., local time, acatastrophic earthquake (MCS maximum intensity = XI,estimated magnitude = 7.1) struck the region of the MessinaStraits, Ionian Sea, Southern Italy. Within minutes after thepassage of the seismic waves, a tsunami with maximumobserved runup of about 10 m hit the coasts of Calabria andSicily (Figure 1) [Platania, 1909; Baratta, 1910; Boschi etal., 1989, 2000]. The earthquake and tsunami caused majordestruction and at least 60,000 deaths. One hundred yearslater, the source of the tsunami is still uncertain. Ourhypothesis is that the 1908 Messina tsunami was not causedby vertical displacement of the seafloor during coseismicrupture as previously thought (www.noaa.gov) but by anunderwater landslide. To test this hypothesis, we analyzedall available tsunami, bathymetric, seismic, and seismolog-ical data to revue previous interpretations and present ournew conclusions.

2. Brief Seismotectonic Setting

[3] Eastern Sicily and southern Calabria (Figure 1) have ahistorical record of destructive earthquakes [Boschi et al.,2000]. These regions lie along the Africa-Eurasia conver-gent plate boundary in the central Mediterranean area,where the Apenninic-Maghrebian orogenic wedge hasgrown since at least the Oligocene. Geodetic and seismo-

logical data show that both the Messina Straits and IonianSea are actively undergoing extension [Goes et al., 2004],possibly in connection with the south-eastward rollback ofthe Ionian slab that is subducting beneath Calabria andSicily. Accordingly, an earthquake has been interpreted asthe source of the 1908 Messina tsunami, with the rupturelocated along a N-to-NE-striking normal fault located in thenorthern sector of the Messina Straits [Boschi et al., 1989;Tinti and Armigliato, 2003]. A N-striking, E-dipping faulthas been recently proposed through a refined inversion ofseismological and geodetic data (Figure 1a) [Amoruso et al.,2006]. Among all the various faults proposed as the sourceof the 1908 Messina earthquake [Tinti and Armigliato,2003], the fault proposed by Amoruso et al. [2006] hasthe southernmost central portion, which is the most tsuna-migenic portion of a fault because it is where the maximumslip occurs.

3. Methods and Results

[4] Immediately after the 1908 Messina earthquake andtsunami, through surveys and numerous interviews andquestionnaires distributed among the survivors, Omori[1909] and Platania [1909] reported the tsunami runupand the delay between the earthquake and tsunami arrivalsfor several cities and villages located along the Calabrianand Sicilian coasts. Afterward, Baratta [1910] conducted anew survey and then combined and compared his data withthose from Omori [1909] and Platania [1909], thus pro-ducing a critically integrated data set of delays between theearthquake and tsunami arrivals. Here we use this data set tofind the tsunami source area. For tsunami runup only, weuse also the data from Platania [1909].[5] Assuming an approximately simultaneous (i.e. within

a few seconds) generation of the earthquake and tsunami asfor example Okal et al. [2003] did for the 1947 Aleutiantsunami, most of the reported delays between the earthquakeand tsunami arrivals correspond to tsunami travel-times. For9 out of a total of 32 sites, the reported tsunami travel-timesare not relevant either because they are not sufficientlyaccurate (i.e. reported in the form such as ‘‘a few minutes’’)or because in these locations the tsunami runup was smalland barely discernible (i.e. runup smaller than 1 m, auxiliarymaterial Table S11). The tsunami travel-times from theremaining 23 sites were processed by a backward ray-tracing method. Tsunami backward ray-tracing analysesbased on historical accounts have been previously successfulin locating the source area of several tsunamis older than theone here studied [e.g. Baptista et al., 1998]. Unlike previousstudies, we do not analyze historical accounts from untrained

1Auxiliary material data sets are available at ftp://ftp.agu.org/apend/gl/2008gl033251. Other auxiliary material files are in the HTML.

GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L06301, doi:10.1029/2008GL033251, 2008ClickHere

for

FullArticle

1Dipartimento di Scienze Geologiche, Universita Roma Tre, Rome,Italy.

2Dipartimento di Scienze della Terra, Universita di Messina, Messina,Italy.

Copyright 2008 by the American Geophysical Union.0094-8276/08/2008GL033251$05.00

L06301 1 of 5

observers; rather, we analyze data collected and processed byscientists, who considered and mitigated possible biases byselecting and properly weighting the eyewitness accounts[Omori, 1909; Platania, 1909; Baratta, 1910]. For instance,accounts by railway station masters and officers of the watch,who were working at the time of events and for whomtemporal observations were important, were consideredparticularly accurate and formed the reference framework[Baratta, 1910]. To account for uncertainty, we present theresults as contours on the density distribution of the backwardray-traced locations (auxiliary material Figure S1). If travel-times and assumptions used in the ray-tracing analysis areaccurate, we would expect a concentration of ray traces in atightly-defined source area (auxiliary material Figure S1).[6] The celerity of shallow water long waves in deep water

is c = (g d)0.5, where g is the gravity acceleration and d isthe local seafloor depth. A preliminary analysis of tsunamidata (i.e. site-by-site runup and travel-times of tsunami,auxiliary material Figure S1) allowed us to find an approx-imate location of the source area of the 1908 tsunami in theIonian Sea off Giardini on the Sicily coast, and off Lazzaroon the Calabria coast (Figure 1a and auxiliary materialTable S1). The tsunami maximum runup and shortesttravel-times were in fact recorded near these locations.The approximate source area for the 1908 Messina tsunamilies at about 2000 m below the sea level and corresponds to

the toe of steep slopes occurring along the Calabrian andSicilian continental margins (Figure 1). By using a seafloordepth of 2000 m, we calculate the tsunami velocity in thesource area to have been about 500 km/h (140.0 m/s).Assuming a decrease of the tsunami velocity with reducedseafloor depth toward the coasts, and assuming a tsunamiminimum velocity (i.e. when hitting the coasts) of about100 km/h (27.8 m/s), we estimate an average tsunamivelocity of about 300 km/h (83.3 m/s). A velocity of about100 km/h for the tsunami close to the coast is appropriatefor steep coasts such as those surrounding the Ionian Sea.By using the average velocity of 300 km/h, we convert thetsunami travel-times (auxiliary material Table S1) for our23 data points into distances from the tsunami source area.By using these distances as radii of circles centered onthe sites to which the tsunami travel-times refer, we find132 locations in the Ionian Sea marking the intersectionsbetween the 23 circles (auxiliary material Figure S1 andTable S2). The locations are concentrated in the sectorabove-defined as the approximate source area of thetsunami (i.e. off Letojanni and Lazzaro, Figure 1), thusvalidating the preliminary location of the tsunami sourceand confirming the general accuracy of the tsunamitravel-time data [Baratta, 1910] and estimated averagevelocity (300 km/h). In this general area and in theadjacent ones, the presence of large debris bodies at the

Figure 1. (a) Map of Ionian Sea and adjacent areas, Southern Italy. Red-to-pink shadings are contours on the densitydistribution of backward ray-traced locations obtained by inverting travel-times of the 1908 Messina tsunami into distances.The complete ray-tracing analysis is shown in auxiliary material Figure S1. Tsunami travel-time data are listed in auxiliarymaterial Table S1. Location coordinates are listed in auxiliary material Table S2. The region with a location density greaterthan 8.9% is here considered the probable area of origin for the tsunami and is indicated with a brown dashed line. Thehypothetical causative fault for the 1908 Messina earthquake is drawn after Amoruso et al. [2006]. (b) Bathymetric map ofthe Ionian seafloor (auxiliary material Figure S2) [Marani et al., 2004]. The probable area of origin for the 1908 Messinatsunami includes a submarine large landslide possibly slid along the Sicilian slope off Giardini, where a landslide scarp andcrown are shown.

L06301 BILLI ET AL.: THE 1908 MESSINA TSUNAMI L06301

2 of 5

toe of the Calabrian and Sicilian continental slopes isinferred from the seafloor bathymetry (Figure 1b). In detail,the tsunami source area we identify includes a large land-slide body with a headwall scarp lying offshore of Giardinion the Sicilian coast (Figure 1b). From the bathymetric map(Figure 1b), at least 20 km3 of displaced material isestimated for this landslide. The Ionian bathymetric mapdoes not show any other large landslide bodies withassociated large scarps and crowns in this region. To thesouth of the landslide shown in Figure 1b, in the largeseafloor re-entrant located off Riposto, we find no evidencefor a landslide and, therefore, this feature is not a collapseniche or at least not a recent one. It is possible that an olderlandslide body is masked by a cover of younger sediments.[7] The CROP-M31 seismic reflection profile across the

Ionian Sea (Figure 2) cuts through the sector consideredhere as the candidate source area for the 1908 Messinatsunami (Figure 1b). In the seismic image, the area inter-preted as the landslide scarp on the seafloor bathymetry isdisplayed as a smooth and curved incline between theSicilian coast and the Ionian bathyal plain, whereas thelandslide body at the toe of the scarp is displayed as achaotic accumulation of material with a very irregular uppersurface (i.e. the seafloor), which is not covered by youngersediments. This evidence suggests a recent age for thecollapse of this chaotic material along the Sicilian slope.A faintly layered body occurs close to the seafloor in theeast of the recently displaced material lying at the toe of theSicilian slope. The seafloor overlying this body is nearlyplanar and horizontal. We interpret this body as a debriscone [Ryan and Heezen, 1965] more compact and, there-fore, older than the adjacent one toward the west. No majorfaults are imaged in the CROP-M31 profile beneath oracross the above-depicted surficial bodies (Figure 2).[8] To determine whether the landslide is a possible cause

of the tsunami, we spatially analyze the related runupreported by Baratta [1910]. In Figures 3a and 3b, weobserve maximum heights in the area of the landslide shownin Figure 1 and a rapid drop toward both the north and thesouth. We observe very similar patterns also by using runupdata from Platania [1909] as reviewed by Tinti [2007](Figures 3c and 3d). The observed spatial pattern of runup

is typical of landslide-tsunamis rather than earthquake-tsunamis [Synolakis et al., 2002]. This is also shown bythe ratio of maximum runup to the width of its distributionalong the coast. This ratio is greater than 10�4 that ischaracteristic of landslide-tsunamis [Okal and Synolakis,2004].[9] Baratta [1910] reports also on the tsunami leading

waves along beaches [Tadepalli and Synolakis, 1994]. Asignificant leading depression was observed along all theSicilian coast, particularly at Scaletta (�150 m), Letojanni(�100 m), Giardini (�200 m), Catania (�200 m), andBrucoli (�200 m). In contrast, along all the Calabrian coast,no significant leading depression was described except atScilla (�30 m), Pellaro (�20 m), and Bova (a few meters)(see localities in Figure 1 and auxiliary material Figure S1).In synthesis, these data indicate a significant leading wavedepression in Sicily and suggest a leading wave elevation inCalabria.

Figure 2. CROP-M31 seismic reflection profile across the Ionian Sea [Scrocca et al., 2004]. Profile track is shown inFigure 1b. TWTT is two-ways-travel-time.

Figure 3. Above, tsunami runup versus distance diagramsalong the (a) Sicilian and (b) Calabrian coasts. Distancescorrespond to the A and B tracks in Figure 1a. Dashed linesare indicative of data trend. Runup data are from Baratta[1910]. (c, d) Same diagrams of Figures 3a and 3b,respectively, drawn by using runup data from Platania[1909] as reviewed by Tinti [2007].

L06301 BILLI ET AL.: THE 1908 MESSINA TSUNAMI L06301

3 of 5

[10] To determine whether the causative fault of the 1908Messina earthquake (Figure 1a) may have triggered thelandslide shown in Figure 1b, we estimate the Coulombstress change produced by the earthquake. Source parame-ters of the causative fault are from the most recentlypublished analyses [Amoruso et al., 2002, 2006]. Theregional extensional stress is modeled assuming an intensityof 40 bar [Jacques et al., 2001] and a N115�E orientation ofthe minimum compressive stress [Goes et al., 2004]. Figure 4shows that the Coulomb stress change in the area of thelandslide is positive between about 0.1 and 0.4 bar. Such astress change is compatible with an earthquake-landslidecausal relationship [e.g., Atakan and Ojeda, 2005].

4. Discussion and Conclusions

[11] Since the catastrophic events of December 1908,there is consensus on the hypothesis that the Messinaearthquake epicenter was located in the northern Ionianregion close to the narrowest section of the Messina Straits(i.e. close to the Messina city, Figure 1), and that thetsunami was concurrently generated by the seafloor dis-placement during coseismic rupture [Tinti and Armigliato,2003]. Macroseismic, seismological, and geodetic data

[Baratta, 1910; Boschi et al., 1989] show that the northernIonian region close to the Messina Straits is beyond doubtthe most suitable location for the causative fault of the 1908Messina earthquake (Figure 1a), but an earthquake alongthis fault does not account for the reported tsunami travel-time and runup data (Figure 3 and auxiliary materialsFigure S1). Although our tsunami ray-tracing analysis maybe constrained by our assumptions concerning the tsunamivelocity, the triangular shape of the Ionian Sea and thetsunami arrival data from the opposite coasts of the IonianSea (Figure 1 and auxiliary material Table S1) allow us tolocate unequivocally the tsunami source in the Ionian Sea offGiardini and Lazzaro (Figure 1). This location is at least40 km in the south of the region where the earthquakemaximum MCS intensity was recorded [Baratta, 1910;Boschi et al., 2000] and is clearly external to the source areaof the earthquake (Figure 1a) [Boschi et al., 1989]. Recentearthquake and tsunami modeling, based on the data collectedsoon after the events, has shown that finding a reliabletsunami source that matches both leveling data and tsunamirunup is very difficult [Tinti and Armigliato, 2003]. This isbecause runup data are much better explained by a sourcesignificantly southward of the source location that accountsfor the leveling data, which can be explained by a causativefault as drawn in Figure 1a, or even further toward the north[Boschi et al., 1989]. The modeling work by Tinti andArmigliato [2003], together with the evidence presented inthis paper indicates that the earthquake caused the surfacedepression but not necessarily the tsunami. Omori [1913]reached this same conclusion. By critically examining thehypothesis that the tsunami was generated by the seafloordisplacement during coseismic rupture, the only suitablealternative to explain the generation of the tsunami is by aunderwater landslide. Our results suggest that an importantalternative candidate for the tsunami trigger is the recentsubmarine landslide located off Giardini (Figures 1 and 2).No further recent landslides are recognized in the studiedportion of the Ionian Sea, thus the landslide off Giardini is theonly possible cause for the 1908 Messina tsunami. Thetsunami runup and leading waves as reported by Baratta[1910] are consistent with this landslide. The runup cannot beaccounted for by the most likely earthquake rupture locationin the north of the area [Tinti and Armigliato, 2003]. Even byignoring the effect of the dynamic stress (i.e. the passage ofthe seismic waves), which is usually far greater than theCoulomb stress change, this latter alone is demonstrated assufficiently effective at triggering the shown landslide(Figure 4).[12] Ryan and Heezen [1965] concluded that, in the

southeastern Ionian basin, at about 150 km from thelandslide observed in Figure 1b, the breakage of subma-rine telegraph cables immediately subsequent to the 1908Messina earthquake is directly associated with a turbiditycurrent, which originated from an underwater avalanchewithin the Messina Straits area. As supporting evidence,they found shallow turbiditic deposits in cores drilled inthe region where the telegraph cables were broken.[13] We conclude that the source for the 1908 Messina

tsunami was not the seafloor displacement during coseismicrupture, as thought previously. The source was a submarinelandslide in the Ionian Sea. This study shows the impor-tance of base research (post-tsunami field surveys in this

Figure 4. Coulomb stress changes at 1.5 km depthproduced by the 1908 Messina earthquake in presence ofa regional stress (indicated by a white arrow). The whiterectangle and line represent the surface projection of theseismogenic fault and the intersection of the fault plane withthe surface, respectively. The black dashed line indicates theprobable area of origin for the tsunami (Figure 1).

L06301 BILLI ET AL.: THE 1908 MESSINA TSUNAMI L06301

4 of 5

case [e.g., Synolakis and Kong, 2006]) consisting of accu-rate data that may result essential in the solution of complexproblems even after a century from the data collection.Also, it improves the statistics of landslide-tsunamis, whichhave often been too simplistically interpreted as sourced byearthquakes [e.g., Tappin et al., 2001].

[14] Acknowledgments. F. Pazzaglia, D. Tappin, and an anonymousreviewer provided invaluable suggestions. Conversations with O. Bellier,E. Boschi, E. Brodsky, F. Florindo, G. Fubelli, M. Parotto, F. Rossetti,and C. Synolakis sharpened our ideas. L. Serva (APAT) is thanked forcopyright permission.

ReferencesAmoruso, A., L. Crescentini, and R. Scarpa (2002), Source parameters ofthe 1908 Messina Straits, Italy, earthquake from geodetic and seismicdata, J. Geophys. Res., 107(B4), 2080, doi:10.1029/2001JB000434.

Amoruso, A., L. Crescentini, G. Neri, B. Orecchio, and R. Scarpa (2006),Spatial relation between the 1908 Messina Straits earthquake slip andrecent earthquake distribution, Geophys. Res. Lett., 33, L17309,doi:10.1029/2006GL027227.

Atakan, K., and A. Ojeda (2005), Stress transfer in the Storegga area, off-shore mid-Norway, Mar. Petrol. Geol., 22, 161–170.

Baptista, M. A., et al. (1998), Constraints on the source of the 1755 Lisbontsunami inferred from numerical modelling of historical data, J. Geodyn.,25, 159–174.

Baratta, M. (1910), La Catastrofe Sismica Calabro-Messinese (28 Dicembre1908), 496 pp., Soc. Geogr. Ital., Rome.

Boschi, E., et al. (1989), Modello di sorgente per il terremoto di Messina del1908 ed evoluzione recente dell’area dello Stretto, in Atti del ConvegnoGNGTS, pp. 245–258, Cons. Naz. Ric., Rome.

Boschi, E., et al. (2000), Catalogue of strong Italian earthquakes from461 B. C. to 1997, Ann. Geofis., 43, 609–868.

Goes, S., et al. (2004), A recent tectonic reorganization in the south-centralMediterranean, Earth Planet. Sci. Lett., 226, 335–345.

Jacques, E., et al. (2001), Faulting and earthquake triggering during the1783 Calabria seismic sequence, Geophys. J. Int., 147, 499–516.

Marani, M. P., et al. (Eds.) (2004), Seafloor bathymetry of the Ionian Sea, inFrom Seafloor to Deep Mantle: Architecture of the Tyrrhenian BackarcBasin, Mem. Descr. Carta Geol. It., vol. XLIV, 216 pp., APAT, Rome.

Okal, E. A., and C. E. Synolakis (2004), Source discriminants for near-fieldtsunamis, Geophys. J. Int., 158, 899–912.

Okal, E. A., et al. (2003), Near-field survey of the 1946 Aleutian tsunamion Unimak and Sanak islands, Bull. Seismol. Soc. Am., 93, 1226–1234.

Omori, F., et al. (1909), Preliminary report on the Messina-Reggio earth-quake of December 28, 1908, Bull. Imp. Earthquake Invest. Comm., 3,37–46.

Omori, F. (1913), Note on the recent sea-level variation at the Italian andAustrian mareograph stations and on the cause of the Messina-Reggioearthquake, Tokyo, Imp. Earthquake Invest. Comm. Bull., 5, 87–100.

Platania, G. (1909), Il maremoto dello Stretto di Messina del 28 Dicembre1908, Boll. Soc. Sismol. It., 13, 369–458.

Ryan, W. B. F., and B. C. Heezen (1965), Ionian Sea submarine canyonsand the 1908 Messina turbidity current, Geol. Soc. Am. Bull., 76, 915–932.

Scrocca, D., et al. (Eds.) (2004), CROP Atlas, 197 pp., APAT, Rome.Synolakis, C. E., and L. Kong (2006), Runupmeasurements of the December2004 Indian Ocean tsunami, Earthquake Spectra, 22, S67–S91.

Synolakis, C. E., et al. (2002), The slump origin of the 1998 Papua NewGuinea tsunami, Proc. R. Soc. London, Ser. A, 458, 763–789.

Tadepalli, S., and C. E. Synolakis (1994), The run-up of N-waves on slopingbeaches, Proc. R. Soc. London, Ser. A, 445, 99–112.

Tappin, D. R., et al. (2001), The Sissano, Papua New Guinea tsunami ofJuly 1998: Offshore evidence on the source mechanism, Mar. Geol., 175,1–23.

Tinti, S. (2007), I maremoti delle coste italiane, Geoitalia, 19, 4–10.Tinti, S., and A. Armigliato (2003), The use of scenarios to evaluate thetsunami impact in southern Italy, Mar. Geol., 199, 221–243.

�����������������������A. Billi, C. Faccenna, R. Funiciello, and L. Minelli, Dipartimento di

Scienze Geologiche, Universita Roma Tre, Largo S. L. Murialdo, 1, Rome,I-00146 Italy. (billi@uniroma3.it)G. Neri, B. Orecchio, and D. Presti, Dipartimento di Scienze della Terra,

Universita di Messina, Pugliatti Piazza, Messina, I-98122 Italy.

L06301 BILLI ET AL.: THE 1908 MESSINA TSUNAMI L06301

5 of 5

Table S1. Coastal localities of eastern Sicily and southern Calabria, Southern Italy, struck by the 1908 Messina tsunami. Tsunami reported travel-time and runup height data are from Baratta [1910]. Used travel-times (underlined localities) are the data used for the tsunami backward ray-tracing shown in Figure S1. Localities are listed by region (Messina to Pozzallo are in Sicily, whereas Reggio Calabria to Gioiosa are in Calabria) and from north to south.

Coastal localities

latitude N longitude E reported travel- time (minutes)

used travel- time (minutes)

reported runup height (m)

reason for data exclusion

Messina 38°11'30'' 15°33'55'' 8.50-10 9.25 2.1-2.7 Paradiso 38°13'36'' 15°34'06'' non-reported non-used 2.4-3.7 unknow time Pace 38°14'08'' 15°34'22'' non-reported non-used 4.7 unknow time Fortino 38°15'55'' 15°39'01'' non-reported non-used 2.8 unknow time Torre Faro 38°15'57'' 15°38'23'' 5-20 non-used 0.7 indefinite time Milazzo 38°13'00" 15°14'57" non-reported non-used 0.7 unknow time Galati 38°06'00'' 15°30'18'' 5-7 6 8 Briga 38°04'37'' 15°29'35'' non-reported non-used 6.3-8.5 unknow time Giampileri 38°03'39'' 15°28'31'' non-reported non-used 7.2 unknow time Scaletta 38°02'23'' 15°27'09'' non-reported non-used 8 unknow time Guidomandri 38°02'56'' 15°28'08'' non-reported non-used 6.4 unknow time Itala 38°02'05'' 15°27'04'' non-reported non-used 7.9 unknow time Alì 38°01'07'' 15°26'26'' non-reported non-used 6.8-8.4 unknow time Nizza 37°59'34'' 15°24'42'' 15 15 9.2 Roccalumera 37°58'26'' 15°23'17'' 6 6 7-8 Furci 37°58'06'' 15°23'03'' 10 10 8 Bucalo 37°57'18'' 15°22'38'' 6 6 6.1 Porto Salvo 37°55'46'' 15°21'16'' non-reported non-used 6 unknow time Letojanni 37°52'55'' 15°18'09'' 4 4 5 Isolabella 37°51'08" 15°17'59" non-reported non-used 4 unknow time Giardini 37°49'43" 15°16'04" immediately non-used 5-8.4 indefinite time Gurna 37°47'05'' 15°14'02'' non-reported non-used 5.6 unknow time Riposto 37°43'54" 15°12'16" 10 10 6 Archirafi 37°42'32'' 15°13'05'' non-reported non-used 5.7 unknow time Pozzillo 37°39'39'' 15°11'46'' non-reported non-used 4.8 unknow time Stazzo 37°38'53'' 15°11'27'' non-reported non-used 4.4 unknow time S. Tecla 37°38'01'' 15°10'31'' non-reported non-used 5.7 unknow time Acireale 37°37'02'' 15°10'10'' 8 8 3.7 Capo Mulini 37°34'36'' 15°10'39'' 5-6 5.5 3.6-4.9 Aci Trezza 37°33'47'' 15°09'45'' 8-10 9 4.6-5.9 Aci Castello 37°33'00'' 15°08'59'' 5 5 3.5 Ognina 37°31'54'' 15°06'55'' 10 10 5 Catania 37°29'58" 15°05'33" 20 20 1.7-2.7 Brucoli 37°17'10'' 15°11'10'' 5 5 1.7 Augusta 37°14'20'' 15°13'14'' 20 20 1.7-2 Siracusa 37°03'53" 15°17'22" 10 10 1.2-1.6 Avola 36°54'50'' 15°09'06'' a few seconds non-used 1.3 indefinite time Calabernardo 36°52'22'' 15°08'04'' 30 non-used 10? uncertain runup Marzamemi 36°44'27'' 15°06'44'' a few minutes non-used 1 indefinite time Cozzo Spadaro 36°41'12'' 15°08'14'' non-reported non-used 1.5 unknown time Pozzallo 36°43'29'' 14°50'32'' non-reported non-used 1.6 unknown time Reggio Calabria 38°06'45'' 15°39'03'' 10 10 6-7 Gallico 38°09'51'' 15°38'49'' non-reported non-used 5.4 unknow time Catona 38°11'01'' 15°38'19'' non-reported non-used 4 unknow time Villa S. Giovanni 38°13'00" 15°38'00" 10-12 11 2.5-3.8 Cannitello 38°13'53'' 15°38'43'' 10 10 1 Scilla 38°15'18'' 15°42'52'' 5-6 5.5 1 Nicotera 38°32'50'' 15°56'02'' 25 non-used non-reported unknown runup Tropea 38°40'53" 15°54'08" non-reported non-used 2.5 unknow time Porto S. Venere 38°42'54'' 16°07'31'' non-reported non-used 1.5 unknow time Pellaro 38°01'19'' 15°38'50'' a few minutes non-used 6-7 indefinite time Lazzaro 37°57'40'' 15°40'22'' non-reported non-used 10 unknow time Capo dell’Armi 37°57'15'' 15°40'44'' non-reported non-used 4 unknow time Melito 37°55'27'' 15°47'09'' a few minutes non-used 3 indefinite time Bova 37°55'50'' 15°55'30'' 10-15 12.5 few metres unknown runup Palizzi 37°55'12'' 15°59'33'' 20 20 3 Gioiosa 38°17'39'' 16°19'31'' a few seconds non-used non-reported indefinite time

Table S2. Coordinates of locations (i.e. circle intersections) shown in Figure S1 and obtained by the tsunami backward ray-tracing.

ID Longitude N (°) Latitude E (°) ID Longitude N (°) Latitude E (°) ID Longitude N (°) Latitude E (°) 1 15.43792278640 37.92336431670 46 15.36044210430 37.69455417740 91 16.12435320420 37.87614952610 2 15.31080604230 37.82772409980 47 15.36891655390 37.69939672010 92 16.16430418090 37.95241957250 3 15.33865066250 37.81561774320 48 15.37375909650 37.69092227050 93 16.19578070800 38.09043203740 4 15.28901460050 37.74903278200 49 15.43186960810 37.55654171250 94 16.19093816540 37.71997752620 5 15.29869968580 37.72845197580 50 15.37981227480 37.49116738700 95 16.18488498710 37.70908180530 6 15.45729295690 37.80714329360 51 15.39433990270 37.43668878240 96 16.19941261500 37.68850099910 7 15.49240139100 37.77566676650 52 15.43186960810 37.39431653440 97 16.30958045980 37.48027166610 8 15.50571838320 37.79503693700 53 15.48755884830 37.46937594510 98 16.22241469250 37.43789941800 9 15.51177156150 37.80472202230 54 15.42218452280 37.48511420870 99 15.56821158980 37.80984257470 10 15.55656508080 37.82772409980 55 15.42460579420 37.49237802260 100 15.57223626640 37.81265984830 11 15.52872046070 37.84951554160 56 15.50087584060 37.50206310790 101 15.58431029630 37.81306231600 12 15.52872046070 37.85556871990 57 15.50087584060 37.50690565050 102 15.58833497290 37.78046243540 13 15.52872046070 37.86525380510 58 15.51056092580 37.50327374350 103 15.59960406740 37.78086490300 14 15.43913342200 37.73571578980 59 15.59530542190 37.45726958860 104 15.59356705250 37.77160814680 15 15.44639723600 37.73813706110 60 15.57835652270 37.43184623980 105 15.60564108240 37.77201061450 16 15.45123977860 37.73208388280 61 15.61830749940 37.41126543360 106 15.61328796790 37.77925503240 17 15.47545249180 37.70181799140 62 15.63646703420 37.40158034830 107 15.61811757990 37.77281554980 18 15.48392694140 37.68365845650 63 15.64130957690 37.43668878240 108 15.62455706250 37.76516866420 19 15.49845456930 37.65339256510 64 15.65099466210 37.42942496840 109 15.62978914210 37.75752177870 20 15.53114173200 37.71876689060 65 15.65583720470 37.44395259630 110 15.61328796790 37.76033905230 21 15.56261825910 37.71392434800 66 15.68368182490 37.42216115450 111 15.62053238590 37.74866749010 22 15.62193940630 37.71150307660 67 15.66673292570 37.37978890650 112 15.60966575900 37.74102060450 23 15.64009894120 37.71150307660 68 15.70305199540 37.35073365070 113 15.60322627640 37.75349710200 24 15.65583720470 37.71150307660 69 15.64373084820 37.33620602280 114 15.63260641570 37.77482788810 25 15.63646703420 37.64249684420 70 15.58198842960 37.32288903060 115 15.63944836600 37.77925503240 26 15.66794356130 37.64370747980 71 15.81321984020 37.39068462740 116 15.64749771920 37.77523035580 27 15.68368182490 37.64370747980 72 15.20427010450 37.51416946450 117 15.65031499280 37.78046243540 28 15.77205822790 37.65702447210 73 15.22000836800 37.33015284450 118 15.66077915200 37.77724269410 29 15.77811140620 37.72482006890 74 15.29991032140 37.31683585230 119 16.24435761370 38.11668788240 30 15.77447949920 37.78777312310 75 15.45366104990 37.22240627100 120 15.11807857560 37.47295403380 31 15.77205822790 37.80593265790 76 15.43550151510 37.31199330970 121 15.28440741630 37.49746338940 32 15.84469636730 37.67518400690 77 15.44276532900 37.30836140270 122 15.28812902590 37.49697370390 33 15.75389869300 37.60012459610 78 15.45123977860 37.31683585230 123 15.29302588080 37.49667989270 34 15.69820945280 37.56622679770 79 15.46092486390 37.32531030190 124 15.29704130170 37.49677782980 35 15.67399673960 37.55533107680 80 15.46455677090 37.31683585230 125 15.31699120730 37.16867292060 36 15.62557131330 37.53475027060 81 15.74542424340 37.89309842530 126 15.36166568010 37.11040186920 37 15.69820945280 37.49600992960 82 15.69942008840 37.85677935550 127 15.38788765320 37.13176792140 38 15.42218452280 37.67397337130 83 15.70184135970 37.86162189820 128 15.39954186350 37.12594081620 39 15.39070799570 37.67034146430 84 15.70789453800 37.86888571210 129 16.04532116880 37.00947422960 40 15.33138684850 37.67397337130 85 15.90764942150 37.76356040990 130 15.83985976870 37.01170750570 41 15.31080604230 37.70302862700 86 15.94275785560 37.84104109200 131 15.48700214670 36.64545022720 42 15.31685922060 37.69697544880 87 16.01418535940 37.88099206870 132 16.33542456850 37.05838297590 43 15.33017621290 37.69818608440 88 16.05655760740 37.84467299900 44 15.35075701900 37.70181799140 89 16.08198095620 37.82288155710 45 15.36044210430 37.70666053400 90 16.11345748330 37.89309842530

�������������������������� ������������ ������������ �������

������������������������

���� ���� ����

������������������������������������������������������������

���������������

���������������������������

���������������������

���������������������

���������������������������� ����� ����� ����

���!��������!��������!��������������������������������

�� �����"����� �����"����� �����"���

#����#����#����

���������������

�����"�������"�������"��

#������#������#������

������������������

���������������

������������������

����$�����$�����$������$������$������$�

#���$���#���$���#���$���#���#���#���

!��������!��������!��������

������������������

��� ���� ���� � �������� �������� �����������������������������

��$����$�� ��$����$�� ��$����$��%���%���%��� �&�&�&

%���"��%���"��%���"�� ���$��� ���$��� ���$���

���'���(����'���(����'���(�

#�����#�����#�����������������������

��!�����!�����!���

���������������������

������������������

�� ������ ������ ����

������������������������

������������

���"�����$����"�����$����"�����$�

���������������������������#�����#�����#�����

���� ���� ����������������������

������������

������������������������

!�����!�����!�����

�������������������������$�)��������$�)��������$�)����

������������#�����#�����#�����

������ ������ ������

�����*��������*��������*���

���������������������

#��������#��������#��������

���� ���� ����

��������$�����������$�����������$���

#������������#������������#������������

!+��'��������������%���$�

%��������

����+

���"���

��������������

����,-.���� �/0.*

����,-.���� �/1.*

����,2.���� �/0.*

����,2.���� �/1.*

/34�

5�+65�+65�+6���������� ������������������������������ �������������������������

��������������������������� ������������ ����������������

����/����/����/

����7����7����7

����/����/����/

����7����7����7

�������������� ��

�

8�7097�/:7�2

19-

/098;7192:-

/39-

191�/

<90

/391

-9,�20�09,�1:<�8

89<�1:0�8

/39009,�0

739/�2:7�2

09/�2

739/�2:7

/39/�7:/�1

/391:2

//97�0:,�-

/39/

0�09/

739,

�����������������������

/39/�7:/�1 ����������������������������������!�����"!��������

,

<

7�0

/�0

1:2

<

0�<

/

/�0

/�1

/3=>?

/�,

<�<0�2

0�2<�-

1

<����$����+90:-�<

0�1

-1�<

2�81�-:-�<

3�2

3�2

1�,:-�0

2�7

7�<:<�2 <�2

7�-

/7�09(�@������

(�@�������9/3

#�������������������������

3:7�7A

7�7:<�<

<�<:1�2

1�2:-�8

-�8://�/

//�/:/,�,

/,�,:/0�0

/0�0:/2�-

/2�-:73

�������$�����+

����������������������

������

������������������

� � ��� � ��� � ��

������ ������� ������� �

��� ��������� ��������� ������

���� ������ ������ ������ ������ ������ ��

���������������������

����� ����� �����

����� ������ ������ �

! "����! "����! "����

# ��$ � # ��$ � # ��$ �

%���&��� %���&��� %���&���

''� ''� ''�

��� ����� ����� ��

���()���()���()

�������������������������

$�"�*$�"�*$�"�*