Lisbon Earthquake Research Articles

Sedimentary record of a tsunami during Roman times, Bay of Cadiz, Spain

AbstractHistorical data show that the Gulf of Cadiz has been exposed to destructive tsunamis during at least the past 2000 yr. The last tsunami was generated by the AD 1755 Lisbon earthquake, which affected the Atlantic coasts of Spain, Portugal and Morocco. Today, these littoral areas are intensely populated and the expected damage could be much greater. Tsunami studies are of great importance in helping to determine the recurrence interval of these events.The presence of washover fan deposits on the inland margin of the Valdelagrana Spit bar (Cadiz, Spain) indicates the occurrence of a high energy marine event ca. 2300 cal. yr BP. Historical, geomorphological, sedimentological, palaeontological and geochronological data suggest that a tsunami could have affected the area during Roman times. Copyright © 2002 John Wiley & Sons, Ltd.

The 1755 Lisbon earthquake

Affecting an area of ca. 800 000 km2 and killing up to 100 000 people, the Lisbon earthquake of 1755 is probably the greatest seismic disaster to have struck western Europe. The shock waves of the earthquake placed a temporary brake on the emerging rationalism of the European Enlightenment and attempts to explain the disaster in terms of human sinfulness coloured many contemporary accounts. Notwithstanding these difficulties, through careful archival research it has proved possible to obtain relatively value-free accounts of most aspects of the earthquake and to use these not only to model the physical characteristics of and damage caused by the earthquake, but also to consider the implications for present day hazard assessment and urban planning. This paper reviews the progress that has been made in: identifying source and faulting mechanisms; the processes involved in the generation and impact of tsunamis; damage caused to different types of building and the use being made of historical earthquakes of different sizes - of which the 1755 event is the largest - in defining future hazard scenarios for Lisbon and other areas of Iberia.

The 1755 Lisbon earthquake

The 1755 Lisbon earthquake

Source of 1755 Lisbon earthquake and tsunami investigated

On November 1, 1755, the city of Lisbon was completely devastated by the combined effect of a tremendous earthquake, tsunami waves, and fire. The 1755 Lisbon earthquake was the most destructive cataclysm recorded in western Europe since the Roman Republic, with an estimated earthquake magnitude Mw ∼8.5 [Martins and Mendes Victor, 1990] and estimated tsunami magnitude of Mt= Mw= 8.5. The earthquake was felt as far away as Great Britain and Finland. The tsunami hit many coastal cities along southwest Iberia and North Africa, causing heavy destruction in Tanger and Casablanca.

Plateau 'pop-up' in the great 1897 Assam earthquake.

The great Assam earthquake of 12 June 1897 reduced to rubble all masonry buildings within a region of northeastern India roughly the size of England, and was felt over an area exceeding that of the great 1755 Lisbon earthquake. Hitherto it was believed that rupture occurred on a north-dipping Himalayan thrust fault propagating south of Bhutan. But here we show that the northern edge of the Shillong plateau rose violently by at least 11 m during the Assam earthquake, and that this was due to the rupture of a buried reverse fault approximately 110 km in length and dipping steeply away from the Himalaya. The stress drop implied by the rupture geometry and the prodigious fault slip of 18 +/- 7 m explains epicentral accelerations observed to exceed 1g vertically and surface velocities exceeding 3 m s-1 (ref. 1). This quantitative observation of active deformation of a 'pop-up' structure confirms that faults bounding such structures can penetrate the whole crust. Plateau uplift in the past 2-5 million years has caused the Indian plate to contract locally by 4 +/- 2 mm yr-1, reducing seismic risk in Bhutan but increasing the risk in northern Bangladesh.

Scilly Isles, UK: optical dating of a possible tsunami deposit from the 1755 Lisbon earthquake

We present the results of optical dating of quartz from marine and aeolian deposits on St. Agnes Island, Scilly Isles, UK. The single-aliquot regenerative-dose protocol was used to estimate the equivalent dose in these samples. Proposed tsunami-laid deposits at Big Pool provided ages of 230±40 and 380±60 years; both are consistent with an expected age of 244 years. An OSL age of 6±3 years was obtained on a modern sub-aqueous beach deposit. These results suggest that the OSL signal in the tsunami-laid quartz was completely reset before deposition, and that these sediments can be dated accurately by optical dating techniques. Sand dunes at Bergecooth, 250 m south of Big Pool, were also dated using OSL. These ages indicate phases of aeolian activity at ∼300 a and 1000 a in the Scilly Isles.

Between Pascal and Mallarmé: Faust's Speculative Moment

THERE IS A TRADITION of Enlightenment discourse that rejects the idea of chance as a crude superstition.' What seems contingent does so-so the argument goes-because we fail to perceive the underlying necessity that gives rise to it. Hume writes, for instance, that the vulgar call chance is nothing but a secret and conceal'd cause.2 In line with this tradition, Goethe frequently expresses distaste for what appears random, chaotic, unstructured. This distaste is evident, for example, in his response to the schrankenlose Willkilr (boundless unpredictability; WA 1.26:42') illustrated by the Lisbon earthquake of 1755a key event in the history of the Enlightenment--and in his unsettled reactions

The Dialogue between Voltaire and Rousseau on the Lisbon Earthquake: The Emergence of a Social Science View

Disasters are usually identified as having occurred at a particular time and place, but they also occur at a particular time in human history and within a specific social and cultural context. Consequently, it is appropriate to call the Lisbon earthquake the first modern disaster (Dynes, 1999). Certainly, earlier history records many instances of geophysical events and the differences among such events were typically explained by variations in their physical intensity. However, the Lisbon earthquake occurred at a time and a place which made it a part of the debate over modernity. Its location in Europe made it a topic in the intellectual debates of the times. These debates had greater impact on the changing cultural context than the physical intensity of the earthquake might imply. The earthquake occurred when there were many strains between tradition and new ideas about progress. It was a time when traditional ideas and institutions were being challenged, when nation states were being created, and when rivalries among states led to tensions and conflict. Further, it was a time when the bonds of traditional religious authority were being challenged by a growing enthusiasm for intellectual freedom and for reason. These major political and institutional shifts were reflected in the meanings that were assigned to the Lisbon earthquake.

Sedimentation and hydrodynamic processes associated with the tsunami generated by the 1755 Lisbon earthquake

An unusual sedimentary horizon, believed to have been deposited by the tsunami associated with the 1755 Lisbon earthquake, has been identified at Boca do Rio in southern Portugal. This horizon marks a distinct sedimentological and micropalaeontological break from the deposits enclosing it. The sedimentary characteristics of the horizon, which consists of several distinct sub-units, vary greatly in both vertical and horizontal section. Detailed textural analysis through vertical sections of these sub-units shows abrupt changes in particle size characteristics. The highly variable nature of the horizon appears to be due to rapid variation in the hydrodynamic characteristics of the depositional event. The lowermost section of the deposit appears to have been deposited from a highly turbulent water mass which was able to transport gravel sized clasts as well as gravel sized mud balls eroded from underlying material. The water mass rapidly lost energy, leading to the deposition of predominantly sand, silt and clay particles. Sharp breaks in textural characteristics are likely to be due to changes in current direction caused by wave reflection or swash–backwash interference. The main sources of sand sized material within the deposit are the seaward barrier (beach–foredune system). The tsunami deposit at Boca do Rio shares many of the sedimentary characteristics of tsunami deposits from other sites around the world.

The tectonic source of the 1755 Lisbon earthquake and tsunami

The SW continental margin of Iberia is affected by several tectonic structures of Cenozoic to Recent age, gen-erated by the dynamics of the Iberia-Africa plate margin. This activity is testified by diffuse seismicity along the eastern portion of the Azores-Gibraltar line. The most important active structure, detected during a reflection seismic survey in 1992, is a thrust-fault, some 50 km long and with dip-slip throw of more than 1 km, located offshore Cabo de S. Vincente. A relocation of historical earthquakes in the area shows that this structure lies very close to the epicentre of the catastrophic 1755 Lisbon earthquake and that it should be the generator of the event. This submarine structure can now be studied for modelization of tsunamis and consequent risk mitigation.

Can hydrodynamic modelling of tsunami contribute to seismic risk assessment ?

In recent years a great effort has been made to quantitatively model major historical events in Europe, searching for models that are compatible with both seismic, hydrodynamic and sedimentological evidences. The possibility to do so, with the available modelling techniques, has been checked against instrumental tsunami and seismological data. Most of this effort has been made within the projects GITEC and GITEC TWO.The quantitavive data that can be gathered from historical sources are: extension of the source area, wave heights, first wave polarity and, only rarely, travel times and time intervals between main waves. With this data the accuracy of source studies is a function of both the model uncertainty (can tsunami waves be accurately modelled ? are seismic parameters compatible with tsunami source parameters ?) and the observation errors. These are large when we deal with historical documents hundreds of years old.Here we present the conclusions obtained from the study on the 1755 Lisbon earthquake and tsunami. The available historical data are reliable enough to allow a good source determination and, surprisingly, the results obtained differ from those obtained from previous macroseismic studies.The analysis of the results obtained in the tsunami modelling, checked against the macroseismic data, allow the identification of an important seismo and tsunamigenic area, close to the SW Portuguese coast, that must also be taken into consideration for the evaluation of seismic hazard.

The 1531 Lisbon earthquake

Abstract In January 1531, the Tagus River Estuary was hit by a strong earthquake, the intensity of which in Lisbon was, according to relevant authors, greater than that of the 1755 earthquake. It was cited by most of the European annalists of the time and was responsible for the destruction of structures, the loss of lives, and enormous panic, thus making it one of the most disastrous earthquakes in the history of Portugal. If we give credit to the detailed descriptions, the maximum intensity was probably X MSK. According to our study, the seismic event was probably caused by the Lower Tagus fault zone (LTFZ). A critical review of reports from the time has allowed us to discredit the claims of the earthquake's effects quite far away from the epicenter. Thanks to this the magnitude remains within moderate limits. On the other hand, the study of the earthquake's effects outside Portugal and the consideration of geological factors have allowed us to produce a reliable isoseismal map. Study of this historical earthquake may greatly influence the design of structures in the rapidly developing area of the Tagus estuary.

A microfaunal and sedimentary record of environmental change within the late Holocene sediments of Boca do Rio (Algarve, Portugal)

The foraminifera and ostracods observed in a late Holocene sedimentary sequence within a fluvial valley at Boca do Rio in the coastal zone of the western Algarve, Portugal, reveal a general, though not smooth transition from marine to fluvial conditions. The relative influence of these two environments appears to depend on the degree of permeability of the barrier system at the coast. Optically stimulated luminescence dates and palaeoecological information obtained from the sequence suggest that barrier formation may be related to changes in climate and/or patterns of ocean current circulation. An unusual deposit rich in sand and gravel found within the otherwise mud-dominated sequence has been dated at AD 1801 ± 76 years. This deposit contains foraminifera and ostracods which indicate marine conditions, and which contrast markedly with the brackish-water, estuarine assemblages found in the mud deposits. The rapid transition in the foraminifera and ostracod assemblages indicates a short-lived coastal flooding, which may represent the tsunami associated with the Lisbon earthquake of AD 1755. The variations in the foraminifera and ostracod assemblages also suggest subsidence during the earthquake, with uplift having occurred in the period since then.

Earthquake Loss Estimation for Europe's Historic Town Centres

To support decision-making on upgrading strategies of historic city centres, loss estimation techniques are needed, suitable for application to masonry buildings. This paper describes the development and application of such techniques to a case study in the Alfama District of Lisbon. The project involved a survey of 200 buildings to investigate structural features and condition, mapped using a GIS system, followed by analysis of key collapse mechanisms to define static collapse loads under horizontal forces for each building. The results, obtained in terms of earthquake ground motions likely to produce equivalent damage, led to the development of vulnerability functions for the case study, verified by comparison with functions derived from statistical analysis of world-wide damage reports and with damage reports of the 1755 Lisbon earthquake. The method is used to predict the reduction in losses achieved by the introduction of low-cost unobtrusive strengthening techniques, such as tie-rods connecting facade walls to floors and cross-walls. Cost benefit analysis, considering only structural costs, indicates that the return on the investment would be considerable.

Court Commissions from the Valadier Workshop

T recent detailed study of a large group of drawings from the workshop directed by the Valadier family of goldsmiths and founderers in eighteenth century Rome has increased· awareness of the diversity of commissions they received from European dynasties and the Papal court. Two exhibi~onsheld in 1991, one in London 1 and the other in Florence2, centred on an album of presentation designs that included works relating to the famous Borghese table service. In 1994 an exhibition at the Musee du Louvre of Valadier works from the museum's own collection3 was mainly a display of mounted hardstones, cameos and gems, both antique and modem,· confiscated by the French forces from occupied Ro.me in 1798, and never returned. Many of the pieces came from the collection of Pope Pius VI (1775-99), one of the most important patrons of the workshop. The recent exhibition in Rome4 included some additional discoveries. The majority of the drawings date from the eighteenth century. A small group is associated with the founder Andrea Valadier, who was born in Aramon in 1694 in Languedoc, settled in Rome after an apprenticeship to a goldsmith in Avignon, and died there in 1759. He left his house and workshop in piazza San Luigi dei Francesi to his two sons Luigi (1726-85) and Giovanni (1732-1805), but the brothers separated in 1762 and the following year Luigi signed a rent agreement for No. 89 via del Babuino. More numerous are the ·drawings identified with Luigi Valadier and his son Giuseppe (1762-1839), who directed the workshop after his father drowned in the Tiber, until he sold it to another family of goldsmiths, headed by Giuseppe Spagna in 1827. An early collaboration between Andrea Valadier and his son Luigi was a commission from King Joao V of Portugal (1689-1750) for gates for the Baptistry of the Patriarchal Church in Lisbon, to enclose a font designed by Luigi Vanvitelli. The gates, exhibited in Rome in 1747 before being sent to Portugal, were destroyed in the earthquake in Lisbon in 1755, with much of the city. The commission has been the subject of many articles in recent years and is likely to be further explored since the discovery of the Weale album, which includes drawings of the gates and other ecclesiastical works ordered by the Portugese king from Rome. 5

Sedimentary processes associated with the tsunami generated by the 1755 Lisbon earthquake on the Algarve coast, Portugal

A distinctive marine deposit at Boca do Rio on the Algarve coast of Portugal occurs up to 1km inland, and exhibits sedimentological and palaeontological characteristics which suggest deposition under high energy conditions. The inland extent of the deposit precludes deposition by even the most extreme storms. The characteristics of the boulders and cobbles in the deposit suggest transport onshore from the zone of wave shoaling into an estuarine environment by long period waves. It is proposed here that the sediment accumulation was deposited by the tsunami generated by the Lisbon earthquake of November 1st, 1755AD.

Rupture extent of the 1755 Lisbon earthquake inferred from numerical modeling of tsunami data

The occurrence of tsunamis, affecting the Portuguese coasts, has been reported since the year 60 BC and the Gorringe bank region has been assumed as the most prone area for tsunami generation in the southwestern Iberian area. The tsunami generated by the 1755.11.01 earthquake is the largest one known in this area, having deeply affected the coasts of Iberia and Morocco. The earthquake, itself, was felt all over Europe, its estimated magnitude being 8.3/4 and its MSK intensity at the epicenter I 0=XI-XII. The great similarity between the isoseismal maps of this event and those of the recent 1969.02.28 earthquake lead several authors to locate the epicenter of the 1755 tsunami close to the Gorringe Bank (cf. Fig 1) and to infer the same type of focal mechanism (e.g. Machado, 1966, Martinez Solares et al., 1979, Levret, 1991) as the one deduced for the 1969 event (Fukao, 1973). The correct identification of the tsunamigenic sources is the essential task for the determination of tsunami risk at the Iberian area. The question we try to answer in the present study is whether or not there is only one major tsunami generating area in the western Iberia as it has been assumed until now. The results obtained here suggest that the 1755 tsunami was probably originated on the continental Iberian shelf, implying an epicentre area located between the Gorringe Bank and the Iberian coasts (cf. Fig. 1), closer to the coast. A complex source is proposed in order to justify tsunami observations in Morocco and seismic intensity values along the lberian and north Morocco coasts

A concise history of mainstream seismology: Origins, legacy, and perspectives

The history of seismology has been traced since man first reacted literarily to the phenomena of earthquakes and volcanoes, some 4000 yr ago. Twenty-six centuries ago man began the quest for natural causes of earthquakes. The dawn of modern seismology broke immediately after the Lisbon earthquake of 1755 with the pioneering studies of John Bevis (1757) and John Michell (1761). It reached its pinnacle with the sobering discourses of Robert Mallet (1862). The science of seismology was born about 100 yr ago (1889) when the first teleseismic record was identified by Ernst von Rebeur-Paschwitz at Potsdam, and the prototype of the modern seismograph was developed by John Milne and his associates in Japan. Rapid progress was achieved during the following years by the early pioneers: Lamb, Love, Oldham, Wiechert, Omori, Golitzin, Volterra, Mohorovicic, Reid, Zoppritz, Hergoltz , and Shida . A further leap forward was gained by the next generation of seismologists, both experimentalists and theoreticians: Gutenberg, Richter, Jeffreys, Bullen, Lehmann, Nakano, Wadati, Sezawa, Stoneley, Pekeris , and Benioff . The advent of long-period seismographs and computers (1934 to 1962) finally put seismology in a position where it could exploit the rich information inheren in seismic signals, on both global and local scales. Indeed, during the last 30 yr, our knowledge of the infrastructure of the Earth's interior and the nature of seismic sources has significantly grown. Yet, an ultimate goal of seismology, namely, the prediction of earthquakes, is not forthcoming. In spite of vast deployment of instruments and manpower, especially in the United States and Japan, no substantial progress has been made in this direction. The nonlinear dynamic processes at the sources of earthquakes are not yet understood, and with the lack of proper mathematical tools and physical theory, breakthrough is not apt to come through computers and seismographs. The conclusion of the present historical study can be succinctly phrased as follows: seismology has reached a stage where its lofty goals cannot be pursued by seismologists alone. Unless we launch a concentrated interdisciplinary research effort, we shall always be surprised by the next major earthquake.

Tsunami sedimentation associated with the Lisbon earthquake of 1 November AD 1755: Boca do Rio, Algarve, Portugal

A description is given of a distinctive marine deposit at Boca do Rio on the Algarve coast of Portugal. It is proposed here that the sediment accumulation was deposited by the tsunami generated by the Lisbon earthquake of 1 November, AD 1755. The deposit exhibits sedimentary characteristics quite unlike other coastal sediment accumulations that are deposited by more moderate wave régimes. These include laterally continuous sand layers, chaotic pebble horizons, large amounts of gravel-sized shell debris and distinctive assemblages of marine microfossils. A preliminary attempt is made here to use the empirical field and laboratory data to define more clearly the processes of coastal sedimentation that characterize tsunami runup. The use of tsunami sediments as time synchronous marker horizons is also discussed.

Walter Benjamin for Children: An Essay on His Radio Years

In light of the legendary difficulty of Benjamin's works, it is a strange and intriguing fact that from 1929 to 1933 the great critic and cultural theorist wrote--and broadcast--numerous scripts, on the order of fireside chats, for children. Invited to speak on whatever subject he considered appropriate, Benjamin talked to the children of Frankfurt and Berlin about the destruction of Pompeii, an earthquake in Lisbon, and a railroad disaster at the Firth of Tay. He spoke about bootlegging and swindling, cataclysm and suicide, Faust and Cagliostro. In this first sustained analysis of the thirty surviving scripts, Jeffrey Mehlman demonstrates how Benjamin used the unlikely forum of children's radio to pursue some of his central philosophical and theological concerns. In Walter Benjamin for Children, readers will encounter a host of intertextual surprises: an evocation of the flooding of the Mississippi informed by the argument of Task of the Translator; a discussion of scams in stamp-collecting that turns into Work of Art in the Age of Mechanical Reproduction; a tale of bootlegging in the American South that converges with the best of Benjamin's essays on fiction. Mehlman superimposes a dual series of texts dealing with catastrophe, on the one hand, and fraud, on the other, that resonate with the false- messianic theology of Sabbatianism as it came to focus the attention and enthusiasm of Benjamin's friend Gershom Scholem during the same years. The radio scripts for children, that is, offer an unexpected byway, on the eve of the apocalypse, into Benjamin's messianic preoccupations. A child's garden of deconstruction, these twenty-minute talks--from theperspective of childhood, before an invisible audience, on whatever happened to cross the critic's mind--are also by their very nature the closest we may ever come to a transcript of a psychoanalysis of Benjamin. Particularly alive to that circumstance, Mehlman explores the themes of the radio broadcasts and brilliantly illuminates their hidden connections to Benjamin's life and work. This lucid analysis brings to light some of the least researched and understood aspects of Benjamin's thought. It will interest and provoke literary theorists and philosophers of culture, as well as anyone who hopes to understand one of this century's most suggestive and perplexing critics.