The Oldest Report of a 1537 Mexico Tsunami Based on Japanese Literature Is Erroneous

According to the Global Historical Database by the National Centers for Environmental Information, the oldest historical tsunami record in Central America is the earthquake tsunami that occurred in Mexico in 1537; however, this record is doubtful because this tsunami is reported by no authority outside Japan. Here, I examined earthquake and tsunami catalogs and found the source of this suspicious data. Imamura (1925) compiled the first part of the chronological table of major earthquakes in the world from the earthquake catalog of the world by Milne (1912). During this compilation, information on the tsunami caused by the 1531 Spain–Portugal earthquake was not copied. The chronological table was published almost annually until 1962; during this time the table was revised in 1958 by Kawasumi, who was the author in charge at the time. The remarks for the 1531 Spain–Portugal earthquake tsunami should have been added during the revision, but the text “tsunami existence” was erroneously added to the next entry for the 1537 Mexico earthquake. The source of the 1537 tsunami report was this miscopy.

Investigating the sedimentary DNA of palaeotsunami deposits in Thailand.

<p>Investigating palaeotsunami deposits is a primary way to extend the tsunami database beyond relatively short instrumental and historical records. Such information is essential to reconstruct the frequency and magnitude of past coastal flooding events, which are a key to assess the impact and risk of tsunami to the coastal community. However, palaeotsunami studies are limited as most of the proxies, such as microfossil and geochemical signals, can be modified or degraded with time. Here, we present the application of DNA analysis to investigate a series of palaeotsunami deposits up to ~2800-years-old from a coastal beach ridge sequence on Phra Thong Island (Thailand). Our result shows that it is possible to accurately discriminate palaeotsunami deposits from intercalating organic mud layers using the microbial communities recovered from DNA preserved in the sediment of the geological record. Our work demonstrates that environmental DNA represents a new and promising tool for investigating historical and pre-historical tsunami records.</p>

Oral legend and geological evidence for a 16th century giant tsunami in Kiribati, central Pacific

<p>Within Oceania, the vast Central and Western Pacific (CEWEP) is an intriguing anomaly because of the scarcity of historical tsunami observations and the complete absence of dated palaeotsunami events.  This study establishes the first dated high-magnitude palaeotsunami event within the CEWEP region.  Both geological data and oral legend are presented for a palaeotsunami that struck remote Makin atoll in northernmost Kiribati towards the end of the 16<sup>th</sup> century.  Narration of the euhemeristic myth by the <em>Wiin te Maneaba</em>, traditional storyteller on Makin, offered important details supporting a tsunami hypothesis.  The legend preserves credible information surrounding the giant-wave origin of <em>Rebua </em>and <em>Tokia</em>, two prominent named subaerial reefblocks of megaclast size that were produced and transported shorewards away from the reef edge by the event.  The youngest U-Th age-dates for fossil coral samples in the reefblocks give a maximum age for the palaeotsunami of <em>circa </em>AD 1576.  Several far-field Pacific Rim and regional possibilities exist for tsunamigenesis.  These include subduction-zone seismicity and catastrophic volcanic eruption, both of which have been linked to late 15<sup>th</sup> century palaeotsunamis recorded elsewhere in the Pacific Islands.  Available evidence, however, suggests that the ~AD 1576 Makin event was more likely locally generated by tsunamigenic submarine slope failure associated with the giant arcuate bight structure that characterises the northern atoll rim.</p>

The Perils of Freshwater Tsunamis

Most people think that tsunamis happen in the sea, but huge events generated by landslides into lakes, rivers, and dams indicate otherwise. For example, during the 563 event in Lake Geneva, a massive fort and numerous towns and villages along its shores were destroyed. There were earlier tsunamis and there will doubtless be more in the future. Indeed, man-made lakes—reservoirs—also represent spectacular dam-building failures. The Vajont Dam in Italy is a story of human folly, a disregard for Nature’s warnings that led to the death of thousands of people downstream. Landslides fall into rivers and can also produce massive waves. New Zealand’s largest historical tsunami was caused by just such a scenario, and although no people died, it offers an ominous sign of what can happen around any water body, fresh or otherwise, in the world.

SIMULATIVE ANALYSIS OF THE PROPAGATION OF A FAR-SOURCE HISTORICAL TSUNAMI ONTO PHILIPPINE COASTS

A simulative analysis methodology is presented and discussed to hindcast the propagation and shallow water transformation of a historical tsunami wave. The initial pulse of water surface induced is numerically modelled based on known geophysical data of earthquake magnitude and seismically induced seabed displacements. The propagation model accounts for the trans-sea movement, long wave propagation and damping, and shallow water transformations but excluding wave runup on the foreshore. The methodology is applied to the Philippine Trench 2012 tsunamigenic event using secondary data from regional geophysical databases and yielded good agreement with observed tsunami heights and arrival times recorded for local and regional locations, particularly at deeper and farther locations from the source.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/SU7IKLh2NDM

A Possible Tsunami Deposit Associated to the CE 1755 Lisbon Earthquake on the Western Coast of Portugal

The CE 1755 Lisbon tsunami was the largest historical tsunami to affect the Atlantic coasts of Europe and North Africa. This study presents the results obtained from the application of different sedimentological techniques (e.g., grain size, morphoscopy, microtextural analysis, geochemistry, radiocarbon dating) on sediments retrieved from the Alcabrichel River alluvial plain (of about 500 m far away from its mouth and approximatively 50 km northwest of Lisbon, Portugal). The results allowed the identification of a sandy layer that was associated with the CE 1755 tsunami. Furthermore, a new microtextural semi-quantitative classification was applied to enhance the identification of extreme marine inundation deposits. Based on sedimentological data, three different tsunami inundation phases were identified, including two inundations and a likely backwash. This innovative work offers physical evidence of the spatial presence of the CE 1755 tsunami event on the western coast of Europe. It also enables a reconstruction of tsunami inundation dynamics, with two flooding waves and an interspersed backwash.

Was Alexandria (Egypt) Destroyed in A.D. 365? A Famous Historical Tsunami Revisited

Ammianus Marcellinus, a fourth-century writer, reported that after an earthquake, on 21 July 365, the sea retreated and then flooded numerous coasts, among them Alexandria (Egypt) and Methoni (southwest Greece). Several other ancient authors seem to mention this event as a “universal earthquake.” The inferred tsunami is usually assigned to reactivation of a fault in the Hellenic (Aegean) Arc, derived from an up to 9 m seismic uplift of Crete. Modeling of this uplift revealed an 8.5+ magnitude earthquake and a tsunami that affected most of the Eastern Mediterranean. For Alexandria, a flooding wave arrival is predicted, and marginal impacts are not excluded because of the topography of the ancient town. On the other hand, ancient sources lead to contradictory results, from no damage to devastation, but new historical evidence indicates that many of the historical reports of the critical period are biased by religious and political ideas, and the Ammianus description was questioned. Hence, for Alexandria there exist three scenarios: major destruction, marginal damage, and no damage by the 365 tsunami. To shed light to this debate (1) ancient sources were analyzed in view of new evidence for their significance, (2) possible impacts of a tsunami in the town’s infrastructure were discussed, and (3) possible impacts of a major destruction were investigated in the framework of the well-known ecclesiastical and civil history of Alexandria. The main conclusions of this study are that (1) no significant tsunami destruction is likely for Alexandria, in agreement with sedimentary evidence, and no major tsunami runup for Methoni; (2) a major earthquake in 365 is likely offshore Crete; and (3) it is inferred that Ammianus brings together two tsunamis, a local slump offshore that produced water retreat and then flooding and local denudation in the eastern Nile Delta, and a second tsunami generated by a fault offshore Crete or in the Ionian and the Adriatic Sea.

Justification of Possible Casualty-Reduction Countermeasures Based on Global Tsunami Hazard Assessment for Tsunami-Prone Regions over the Past 400 Years

Tsunami hazards can be considered as multiregional in their impacts, as transoceanic waves can propagate beyond local areas, as evidenced in recent tsunami events, e.g., the 2004 Indian Ocean and 2011 Great East Japan tsunamis. However, in a single event, the characteristics of a tsunami (wave amplitude and arrival time) can differ from location to location, due to a myriad of reasons including distance from the source, bathymetry of the seafloor, and local effects. Tsunami countermeasures cannot be similarly applied globally. It is prudent to investigate tsunami hazard characteristics at a regional scale in order to evaluate suitable tsunami countermeasures. On this basis, approximately 300 major historical tsunamis have been reproduced in this study based on seismic records over the last 400 years. In this study, numerical analysis was performed to reproduce tsunami waveforms at each global tidal station, and numerical results were verified by comparing them with the 2011 Great East Japan tsunami record data. Non-structural tsunami countermeasures were proposed and selected for each region based on two main criteria – wave amplitudes and arrival times. Evaluation of selected countermeasures indicate that planning for evacuation processes (such as evacuation route mapping, signage and evacuation drills) are important in all situations. For local large tsunamis, evacuation drills are essential to ensure a community is well prepared for self-evacuation due to the short amount of time available for evacuation. Early warning systems were most effective where tsunamis are of large and distant origins. On the other hand, it would be more appropriate to invest in public alert systems for tsunamis of smaller magnitudes. Using these selection criteria, combinations of countermeasures were proposed for each region to focus their attention on, based on the simulated results of the historical tsunami events. The end-goal of this study is to inform decision-making processes and regional planning of tsunami disaster management.