Emanuela Guidoboni

Tsunami Hazard Evaluation of the Eastern Mediterranean: Historical Analysis and Selected Modeling

Seismic sea waves in the eastern Mediterranean have been reported since written history first emerged several thousand years ago. We collected and investigated these ancient and modern reports to understand and model the typical tsunamigenic sources, with the ultimate purpose of characterizing tsunami hazard along the Levant coasts. Surprisingly, only 35% of the tsunami reports could be traced back to primary sources, with the balance remaining questionable. The tsunamis varied in size, from barely noticeable to greatly damaging, and their effects ranged from local to regional. Overall, we list 21 reliably reported tsunamis that occurred since the mid second century b.c. along the Levant coast, along with 57 significant historical earthquakes that originated from the “local” continental Dead Sea Transform (dst) system. An in-depth evaluation shows that 10 tsunamis are clearly associated with on-land dst earthquakes, and therefore, as formerly suggested, they probably originated from offshore, seismogenically induced slumps. Eight tsunamis arrived from the “remote” Hellenic and Cypriot Arcs, one from Italy, and two are left with as yet unrecognized sources. A major conclusion from this work is that onshore earthquakes commonly produce tsunamis along the Levant coastline, and that analogous situations are present elsewhere in the Mediterranean, as well as along the California coast and in another regions with active faults near the coast. We modeled three typical scenarios, and in light of the Sumatra experience, we examined the more likely severe magnitudes. This of course leads us toward the upper range of expected run-ups. The models show that sooner than five minutes after a strong earthquake produces an offshore slump, which occurs after close to a third of the large dst earthquakes, a 4- to 6-m run-up may flood part of the Syrian, Lebanese, and Israeli coasts. Tsunamis from remote earthquakes, however, arrive later and produce only 1- to 3-m run-ups, but are more regional in extent. Online material: Tsunami modeling and reports.

The large earthquake of 8 August 1303 in Crete: seismic scenario and tsunami in the Mediterranean area

By conducting a historical review of this large seismic event in the Mediterranean, it has been possible to identify both the epicentral area and the area in which its effects were principally felt. Ever since the nineteenth century, the seismological tradition has offered a variety of partial interpretations of the earthquake, depending on whether the main sources used were Arabic, Greek or Latin texts. Our systematic research has involved the analysis not only of Arab, Byzantine and Italian chronicle sources, but also and in particular of a large number of never previously used official and public authority documents, preserved in Venice in the State Archive, in the Marciana National Library and in the Library of the Museo Civico Correr. As a result, it has been possible to establish not only chronological parameters for the earthquake (they were previously uncertain) but also its overall effects (epicentral area in Crete, Imax XI MCS). Sources containing information in 41 affected localities and areas were identified. The earthquake also gave rise to a large tsunami, which scholars have seen as having certain interesting elements in common with that of 21 July 365, whose epicentre was also in Crete. As regards methodology, this research made it clear that knowledge of large historical earthquakes in the Mediterranean is dependent upon developing specialised research and going beyond the territorial limits of current national catalogues.

Seismic analysis of the Asinelli Tower and earthquakes in Bologna

Abstract The existence of a valuable historical heritage of the Medieval age in Bologna has motivated a deeper study on the seismic behaviour of the Asinelli Tower, which, beyond being the town symbol, has a structural configuration prone to seismic damage. Accordingly, in the present paper, the seismicity of Bologna is reviewed and a synthesis of the damage observed in the urban area, based on an accurate historical research, is given, with the objective of evaluating the behavior of the Asinelli Tower within the framework of the effects localized in the municipality. An assessment of the towers stability with respect to compatible seismic events, at least qualitatively, with the region seismicity is then carried out by means of a non-linear dynamic analysis on a simplified model.

Identification of Amplified Damage Zones in Palermo, Sicily (Italy), during the Earthquakes of the Last Three Centuries

The damage scenario for the city of Palermo has been reconstructed for the three most damaging earthquakes that have occurred since the eighteenth century (1 September 1726; 5 March 1823; 15 January 1940). Research has been carried out on the original written documents, mostly kept in the archives of administrative and clerical institutions in Sicily. The chance to collate and compare the information coming from the different coeval sources provides an assurance as to the reliability of the collected data and optimizes the information framework. All the damage episodes have been pinpointed in the ancient urban pattern of the city. The historic urban area has been divided up using a grid with square-module geometry, each grid element being 100 × 100 m in size. The resulting damage distribution shows a systematic amplification of effects in some of the grid elements. In order to formulate an interpretation of the damage anomalies in terms of near-surface geology, a geographic information system (GIS) has been used to handle a geological database of about 2000 geo-referenced soil profiles in Palermo. This approach has provided us with a quick 2D and 3D visualization of the upper-layer structure in the study area. As expected, a close correlation was found between the zones of major damage and the thickness of recent deposits characterized by weak cohesiveness and high compressibility: the damage level increases at sites where thickness exceeds a 12-m threshold. The strongest effects occur on water-saturated deposits thicker than 22 m. In terms of the macroseismic effects, a transition from the hardest (Oligo-Miocene Numidian flysch and calcarenites) to the softest ground (recent alluvial deposits and man-made fill) present in the historic center of Palermo implies a difference in Mercalli Cancani Sieberg (MCS) intensity by one to two degrees during the same earthquake. An M 5.6 earthquake occurred off the Palermo coast on 6 September 2002 subsequent to our analysis of the macroseismic data. The instrumental data from this most recent shock provide a posteriori experimental evidence of significant ground-shaking variations between the different geological formations. This validates the macroseismic results and indicates that research and applications based on crossing different datasets can be successfully performed for urban areas using GIS technology. Manuscript received 25 June 2002.

The “exceptional” earthquake of 3 January 1117 in the Verona area (northern Italy): A critical time review and detection of two lost earthquakes (lower Germany and Tuscany)

In the seismological literature the 3 January 1117 earthquake represents an interesting case study, both for the sheer size of the area in which that event is recorded by the monastic sources of the 12th century, and for the amount of damage mentioned. The 1117 event has been added to the earthquake catalogues of up to five European countries (Italy, France, Belgium, Switzerland, the Iberian peninsula), and it is the largest historical earthquake for northern Italy. We have analyzed the monastic time system in the 12th century and, by means of a comparative analysis of the sources, have correlated the two shocks mentioned (in the night and in the afternoon of 3 January) to territorial effects, seeking to make the overall picture reported for Europe more consistent. The connection between the linguistic indications and the localization of the effects has allowed us to shed light, with a reasonable degree of approximation, upon two previously little known earthquakes, probably generated by a sequence of events. A first earthquake in lower Germany (I0 (epicentral intensity) VII–VIII MCS (Mercalli, Cancani, Sieberg), M 6.4) preceded the far more violent one in northern Italy (Verona area) by about 12–13 hours. The second event is the one reported in the literature. We have put forward new parameters for this Veronese earthquake (I0 IX MCS, M 7.0). A third earthquake is independently recorded in the northwestern area of Tuscany (Imax VII-VIII MCS), but for the latter event the epicenter and magnitude cannot be evaluated.

Aims and methods in territorial archaeology: possible clues to a strong fourth-century AD earthquake in the Straits of Messina (southern Italy)

Abstract This research was stimulated by the need to extend in time the record of Italy’s largest earthquakes, which commonly have repeat times of the same order as the length of the available historical record. As a test case we used the 1908 Straits of Messina earthquake, a large event that geologists assume to recur at intervals of roughly a millennium but whose predecessors are as yet unknown. The 1908 earthquake caused enormous territorial upheaval and left signs in the settlements that are still largely recognizable today. We hypothesized that the Straits of Messina, which were densely populated even in ancient times, may similarly retain evidence of one or more much older ‘upheavals’ of the settlement network, and that this evidence may be recognized through a careful analysis of archaeological observations. We found evidence that the settled area around the Straits of Messina contracted substantially around the middle of the fourth century AD, when many sites were abandoned or relocated. This contraction can hardly be justified by the then current economic and military setting. Specific archaeological findings within the cities of Messina and Reggio Calabria also suggest a serious decline of the region during the same period. The archaeological hypothesis is in good agreement with the available historical and palaeoseismological evidence and suggests that a large earthquake, perhaps similar to the 1908 event, took place in the area surrounding the Straits of Messina around the middle of the fourth century AD.

The 1138–1139 and 1156–1159 destructive seismic crises in Syria, south-eastern Turkey and northern Lebanon

The aim of this study is to shed light ontwo important destructive seismicsequences, about 20 years apart (1138–1139and 1156–1159), which hit the northernsector of the Dead Sea transform faultsystem (DSTFS), in the easternMediterranean region. Although some ofthese earthquakes were already known to thescholarly tradition, the interpretationsprovided until today have largely beenpartial and characterised by uncertaintiesand discrepancies among the variousauthors. Our study has developed throughresearch into the original Arabic, Syriac,Armenian and Latin texts and a criticalanalysis relating to a territory fragmentedby the presence of the Christian-Latinstates. This analysis has allowed us toshed light on the already existing, albeitoften uncertain, information and to add newelements of these two important series ofearthquake shocks to our knowledge base.As regards the first seismic sequence(October 1138–June 1139), apart from havingdefined the date with greater accuracy,eight new locations affected have beenidentified, unknown to previous studies.The shocks jolted a vast area withdestructive effects, including theterritory of Aleppo (modern Halab, Syria)and the western part of the region ofEdessa (modern Urfa, Turkey).The second seismic sequence (September1156–May 1159) was much longer anddevastating, and hit a huge area, includedbetween the present-day territories ofnorth-western Syria, northern Lebanon andthe region of Antioch (modern Antakya, insouthern Turkey). A detailed analysis ofthe primary sources has allowed toreconstruct the series of shocks withchronological detail of the effects,improving our previous knowledge. Lastly,the authors formulate an hypothesis as tothe possible seismogenic zones affected.

Vesuvius before the 1631 eruption

of which a printed transcription will shortly be published [Guidoboni, 2006], provided new data concerning the activity of Vesuvius 60 years prior to its last great eruption, on 16 December 1631. This activity, which had until now been unknown to modern science, calls for a re-evaluation of the current conditions of the volcano and of possible precursors to the next major eruption. Vesuvius is one of the most dangerous volcanoes in the world: Its activity can affect an area comprising 18 municipalities that are inhabited by more than 700,000 people in an area less than eight kilometers away from the volcano vent. The volcano has been dormant since 1944, but the history of Vesuvius has been punctuated by violent and destructive, albeit infrequent, Plinian-type explosive eruptions, during which material is continuously ejected at a high velocity and at a great height (up to a few tens of kilometers) from the vent, forming a typical eruptive column with an umbrella cloud. In the past 3500 years, in between one Plinian eruption and the following one, several minor eruptive events have taken place, ranging from subplinian eruptions to more or less violent Strombolian activity and lava flow emissions.

Encoding and computer analysis of macroseismic effects

Abstract We propose a method for the encoding and the computer analysis of the macroseismic effects deduced from historical sources allowing the complete formalization of the process of seismic intensity assessment. In the framework of historical sismology we make use of a multi-criteria decisions-support algorithm, based on the theory of the Fuzzy Sets. By analyzing the texts of the available sources for the 1919 Mugello and 1920 Garfagnana earthquakes, we followed a classification criterion which is independent of any macroseismic scale: we “disarrange” each sentence reported on the sources into 5 syntactic elementary components and represent it by a set of alphanumeric codes. This allows us to retain the maximum adherence to the original sources and to avoid forced interpretations and losses of information due to the need of fitting a given description to each observed effect. Moreover this scheme also allows to gather equivalent effects by reassigning them the same code, and to use this new classification in further processing. This procedure could even be seen as an attempt to define a new macroseismic scale on the basis of a statistical counting of different effects occurrences.

The Most Ancient Maps of Erupting Mount Etna

Mount Etna, in eastern Sicily, Italy, is an active volcano on whose slopes are the city of Catania and several towns. The volcano, whose eruptions are noted in written sources dating back to the thirteenth century B.C., continues to hold surprises for researchers who examine its eruptive history. During extensive historical research for a new catalog of Etnas eruptions (E. Guidoboni and E. Boschi, manuscript in preparation, 2008), two maps have been found that previously were unknown in the literature. These maps, which are the most ancient ones that represent Mount Etna erupting, provide new elements to evaluate the eruption that started on 19 December 1634 and continued until June 1636.