Tsunami Geology

An 8th century CE earthquake severely damaged inland cities across the southern-central Levant, but reported evidence of this earthquake along the coastline is scarce. In Caesarea Maritima, archaeologists have found contemporaneous anomalous sand and shelly layers within nearshore structures and interpreted them as construction fill, aeolian accumulation, or abandonment debris. Recently, similar sand deposits were exposed in a Roman-to-Islamic harbor-side warehouse. This presented the first opportunity to directly sample and systematically analyze in situ, undisturbed deposits in order to determine their origin and taphonomic (source and transport) history. Two sediment cores from the deposit as well as comparative reference samples from defined contexts were analyzed for grain size distribution, foraminifera (abundance/taphonomy), and relative age (POSL, archaeochronology). The results support the interpretation that the deposit was formed from the transport of offshore marine sedi...

The morphology of beach ridge plains along active margins can be used to reconstruct coastal subsidence during large megathrust earthquakes. Here we use satellite imagery and automatic level surveys to reconstruct the build-up of a new beach ridge along a 10 km long stretch of the western Acehnese coast after the complete destruction of the beach during the great Sumatra -Andaman earthquake and successive tsunami in December 2004. The western Acehnese coast is characterized by ridge and swale topography reflecting the long-term progradation of the coastline. Radiocarbon dates obtained from marshy deposits in between ridges indicate an average progradation rate of 1.3e1.8 m per year over the last 1000 years. As a result of coseismic subsidence of 0.5e1 m and tsunami inundation in 2004, the most seaward beach ridge was destroyed and the coastline receded on average 110 m landward representing 65e85 years of average progradation. However, by 2006 a new 22 m wide ridge had formed. In the following years the coast prograded by an additional 30 m, but has not yet recovered to its pre-December 2004 position. In addition to the spatial data, topographic surveys conducted in 2009, 2012 and 2013 indicate that the crest of the newly formed beach ridge is 0.8e1.3 m higher than the crests of older beach ridges further inland. The source material for the new ridge is most likely sand transported seaward by the back flow of the 2004 tsunami and stored on the upper shoreface. In the months and years after the tsunami, this sediment is reworked by regular coastal processes and transported back to shore, leading to the reconstruction of a higher beach ridge in equilibrium with the vertical displacement of the coast and the resulting higher relative sea level. The preservation potential of the newly formed ridge depends on sediment availability within the coastal system to balance coastal profile adjustments due to rapid postseismic uplift. In Aceh, the preservation of seismically modified beach ridge morphology seems likely and another prominent ridge can be found in 640 m distance to the shoreline. It most likely formed in the aftermath of a previous megathrust earthquake and tsunami about 600 years ago matching sediment and coral records for this region.

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Preliminary estimate of the scale of the Mega Tsunami in Antarctica (Ed 4s 30.01. 2023)ENGl Preface Unfortunately, it turned out that the text was damaged, so I had to make a fourth revision. One of the reason for creating this edition was two photos from Antarctica. Both have valleys, one at an altitude of 1181 m and the other at an altitude of 1772 m. Young water layers are visible on both. There is only one reason in this case, the final tsunami, stray water flows (Fg.11) After some time, my colleague, my fellow blogger from Norway, but Ukrainian by origin, created a talented video on this topic, which presented the problems and their solutions much more widely. It is interesting that in the comments to it, the audience has almost no doubts about the reality of the problems shown. This prompted me to write this article. Its purpose was to focus on the considerable amount of material that corroborates the events. But at the last moment, a question arose that had not been raised at all from the beginning. According to Soviet terminology, these are Kurumas, and according to Western terminology, they are running stones, or similar terminology. Here This Video https://www.youtube.com/ watch?v=35gsIUjVJcg This article is a continuation and conclusion of the problem raised a few months ago:-How is science done! On the example of a study of the Mega Tsunami in the ice-free part of Antarctica. It considered and revealed the causes of the phenomenon, which explained the presence of seal mummies in the ice-free part of Antarctica (Fig. 1). Moreover, the mummies were at a distance of up to 60 km from the shore and altitudes up to 1800 m above sea level. The facts of finding the mummies were discovered in 1900, but the reasons have not been established.. Further in this work is the text about the tragic death of seals and examples of geological and geomorphological objects typical for different parts of the globe in Antarctica.

Optical dating of liquefied sand structures formed during major earthquakes in Upper Assam, northeast of India, has been carried out to constrain the timing of prehistoric earthquakes in this seismically active region. The bleaching of source material and of the same material during the creation of a liquefaction feature was tested using quartz extracted from 21 samples associated with two different liquefaction structures in Upper Assam. Due to the poor sensitivity of quartz from this region, a sensitisation procedure was used in our SAR protocol to reduce the scatter in optical ages. Various internal consistency tests of the measurement protocol and the excellent reproducibility of the OSL ages indicate that the dose estimates from the quartz are accurate and the optical ages reliable. The preliminary OSL ages indicate that the liquefaction features were formed between 1430 AD and 1630 AD. This study demonstrates that using OSL, 'direct dating' of prehistoric earthquakes may be possible, if sand blows from liquefied dykes are preserved.

Tsu nami de pos its have not pre vi ously been re corded along the south ern coast of the Bal tic Sea. The re sults of pres ent research pro vide ev i dence of high-en ergy event lay ers that oc cur on the bot tom of two hemi spher i cal hol lows cut into glaciolimnic silt and glaciofluvial sand and gravel of Late Weichselian age. The event de pos its are rep re sented by poorly sorted ma rine sand with ad mix tures of peb bles and allochthonous biogenic de tri tus: ma rine, brack ish and oc ca sion ally fresh wa ter shells and shell de bris of bi valves and snails, plant macrofossils from the nearshore zone, shreds and lumps of peaty ma te rial, gyttja and organogenic silt, lumps of char coal, wood pieces and tree branches and trunks. All these fea tures are com monly con sid ered in dic a tive of tsu na mis. The age of the biogenic de tri tus found in the tsu nami layer ranges from 6,630 to 10,390 cal. yr BP, whereas the old est gyttja cov er ing the event lay ers is 6,600 cal. yr BP old. This means that the tsunami oc curred be tween 6,600 and 6,630 cal. yr BP. Var i ous causes of the tsu nami event are con sid ered, in clud ing the impact of me te or ites within the coastal plain and the lit to ral zone of the south ern Bal tic Sea.

The 26th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified a...

Geoslicer is a field gear for active fault geology studies invented in Japan, in 1997. It was formerly addressed to overcome some difficulties in studying active faults. Lately, it has also been applied for tsunami, geological, liquefaction geology, geo-archaeology, and Quaternary geology in common. Despite evidently effective in those studies, it still bears several disadvantages. Several modifications and developments have been implemented to eliminate these disadvantages. A new type geoslicer was invented as a result, Extendable Geoslicer. This new type geoslicer has been tested and showed good performance in relation with the disadvantages of the old type. Extendable geoslicer is evidently operated more easily, cheaper, handier, and works in all field types.

The December 2004 Sumatra-Andaman tsunami prompted an unprecedented research effort to find ancient precursors and quantify the recurrence time of such a deadly natural disaster. This effort, however, has focused primarily along the northern and eastern Indian Ocean coastlines, in proximal areas hardest hit by the tsunami. No studies have been made to quantify the recurrence of tsunamis along the coastlines of the western Indian Ocean, leading to an underestimation of the tsunami risk in East Africa. Here, we document a 1000-yr-old sand layer hosting archaeological remains of an ancient coastal Swahili settlement in Tanzania. The sedimentary facies, grain-size distribution, and faunal assemblages indicate a tsunami wave as the most likely cause for the deposition of this sand layer. The tsunami in Tanzania is coeval with analogous deposits discovered at eastern Indian Ocean coastal sites. Numerical simulations of tsunami wave propagation indicate a megathrust earthquake generated by...

The December 26, 2004 Sumatra earthquake's epicenter was 163 kms away from Great Nicobar, the southern most island from the archipelago and hence it was strongly felt in the entire Andaman & Nicobar group of islands including Car Nicobar. 3400 people have lost their lives and most of the vital infrastructure were completely destroyed. The presents study aims to understand the vulnerability of the Car Nicobar coast to tsunami hazard from varied sources by using numerical model of tsunami propagation and run-up and compare it with the field data on inundation collected immediately after the tsunami using real time kinematic GPS. A tsunami vulnerability database has been builtup by modelling the past earth quakes recorded in this region. Elevation data collected using Airborne Laser Terrain Mapper (ALTM) was used to generate the inundation scenarios. A GIS database on the tsunami vulnerability of Car Nicobar to tsunami hazard is generated which would be immense use in mitigation and planning.

The Chilean tsunami of 22 May 1960 reamed out a breach and built up a fan as it flowed across a sparsely inhabited beach-ridge plain near Maullín, midway along the length of the tsunami source. Eyewitnesses to the flooding, interviewed mainly in 1988 and 1989, identified levels that the tsunami had reached on high ground, trees, and buildings. The maximum levels fell, from about 10 m to 2 m, between the mouth of the tidal Río Maullín and an inundation limit nearly 5 km inland across the plain. Along this profile at Caulle, where the maximum flow depth was a few meters deep, airphotos taken in 1961 show breaches across a road on a sandy beach ridge. Inland from one of these breaches is a fan with branched distributaries. Today its breach holds a pond that has been changing into a marsh. The 1960 fan deposits, as much as 60 cm thick, are traceable inland for 120 m from the breach. They rest on a pasture soil above two additional sand bodies, each atop its own buried soil. The earlier of the pre-1960 sand bodies probably dates to AD 1270-1400, in which case its age is not statistically different from that of a sand sheet previously dated elsewhere near Maullín. The breach likely originated then and has been freshened twice. Evidence that the breach was freshened in 1960 includes a near-basal interval of cobble-size clasts of sediment and soil, most of them probably derived from the organic fill of pre-1960 breach. The cobbly interval is overlain by sand with ripple-drift laminae that record landward flow. The fan of another breach near Maullín, at Chanhué, also provides stratigraphic evidence for recurrent tsunamis, though not necessarily for the repeated use of the breach. These findings were anticipated a half century ago by description of paired breaches and fans that the 1960 Chilean tsunami produced in Japan. Breaches and their fans may provide lasting evidence for tsunami inundation of beach-ridge plains. The breaches might be detectable by remote sensing, and the thickness of the fan deposits might help them outlast an ordinary tsunami sand sheet.

A morpho-geophysical investigation of two beaches in Thailand over the last decade shows that they have completely recovered from the 2004 Indian Ocean tsunami (IOT) without any human intervention. Although the beach systems show contrasting styles of recovery in both cases natural processes have reconstructed the beaches to comparable pre-tsunami morphologies in under a decade, demonstrating the existence of punctuated equilibrium in coastal systems and the resilience of natural systems to catastrophic events. Through a combination of remote sensing, field surveys and shallow geophysics we reconstruct the post-event recovery of beaches at Phra Thong Island, a remote, near pristine site that was severely impacted by the IOT. We identify periods of aggradation, progradation and washover sedimentation that match with local events including a storm in November 2007. The rapid recovery of these systems implies that majority of sediment scoured by the tsunami was not transported far offshore but remained in the littoral zone within reach of fair-weather waves that returned it (the sediment) to the beach naturally.

Sandy onshore deposits from tsunamis are difficult to distinguish from storm deposits, which makes it difficult to assess coastal hazards from the geological record. Here we analyse environmental DNA from microbial communities preserved in known tsunami and storm-deposited sediments and intercalating soils and non-marine sediments near Cuddalore, India, and Phra Thong Island, Thailand. Both sites were impacted by the 2004 Indian Ocean Tsunami and a subsequent storm flooding event (2011 Cyclone Thane at Cuddalore and a 2007 storm at Phra Thong Island). We show that the microbial communities in the overwash deposits are significantly different from soil and sediments that are not derived by overwash processes at both locations. Our method also successfully discriminates between modern tsunami deposits and storm deposits. We suggest molecular techniques have the potential to accurately discriminate overwash deposits from catastrophic natural events.

Identification of extreme events in the sedimentary record relies on the correct characterisation of the deposit by means of multiple parameters and different diagnostic criteria. Multiple proxies based on well-tested geological, biological, and chemical analyses have been used to distinguish tsunami layers from other marine extreme events. However, few proxies distinguish or compare the "degree of sedimentary chaos" of an event relative to background sediments and between other extreme events. In this pilot study, the potential of Optically Stimulated Luminescence (OSL), normally used as a dating method, is demonstrated and a new potential sedimentological proxy is proposed when analysing in depth the OSL signal from single grain measurements to distinguish between underwater deposits derived from marine extreme events embedded in the texturally and compositionally homogeneous shallow shelf archive of the eastern Mediterranean. Newly and previously collected sediment samples from underwater excavations and a sediment core offshore Caesarea Maritima (Israel) were used in this experiment. Each sample was associated with either tsunami, storm, or fair weather (normal) marine conditions based on multiple proxies. In this study, single grain over-dispersion (SG-OD) values and ranges are used as a potentially novel way to quantify the degree of sedimentary chaos, thus the degree of scatter of the dose distribution as a function of the efficiency of exposure to sunlight (zeroing) of the quartz grains entrained during transport and deposition. Given that turbidity of a fluid should be associated with lower light penetration, and higher energy flow with greater sediment density (as can occur in tsunamis relative to storms), these conditions should be reflected in variations in single grain over-dispersion values, hence identifying luminescence distribution patterns related to known depositional conditions. This quantification is coupled with detailed statistical analysis of the resulting single grain equivalent dose distributions, minimally used in OSL-dating. Three types of underwater deposits were categorised based on three distribution typologies, to which, preliminary, conservative single grain over-dispersion ranges were assigned: b25% for Gaussian-like sands deposited under normal marine conditions; 25-60% for storm-laid sediments depicting bimodal distributions; and N60% for tsunami-related deposits showing asymmetric distributions with strong positive skewness. This new tool provides a means to study offshore extreme marine events, without potential dismissal of other identification criteria and proxies. Based on these results, single grain over-dispersion OSL could be considered as a potential new sedimentological proxy for identification, comparison and characterisation of marine-derived extreme events in the shallow shelf (such as tsunami deposits), as it is intrinsic to the sediment grain, and the degree of sedimentary chaos of the event itself.

To evaluate the potential of optical dating (OSL) in establishing a proper tsunami chronology for Phra Thong Island (SW Thailand), the method was applied to a suite of tsunamigenic and littoral sandy deposits, for which independent age control was available. Small aliquots of coarse grained quartz were used for measurements, and processed statistically by means of appropriate age models. Based on the equivalent dose distributions, the well bleached littoral deposits were analysed with the central age model (CAM); the tsunamigenic samples revealed poor bleaching, thus, the minimum age model (MAM) was applied. The cross-check with independent age data showed good agreement between luminescence ages and the existing radiocarbon chronology for the littoral deposits. The poorly bleached deposits of the 2004 Indian Ocean tsunami revealed residuals of less than 40 years, which are insignificant for older deposits and demonstrate the general suitability of the dating technique for tsunamites on Phra Thong. Afterwards, the approach was extended to tsunamigenic and littoral sediments of unknown age. Since those revealed properties similar to their reference deposits, the procedures of statistical D e determination were adopted. The resulting ages were in agreement with the stratigraphical position and (largely) with the wider chronological context.

The Holocene beach-ridge plain of Phra Thong Island (Ko Phra Thong, SW Thailand) provides sedimentary evidence of several palaeotsunamis, in addition to the deposit of the 2004 Indian Ocean tsunami. Due to poor preservation conditions, these palaeoevent layers are restricted to swales. Correlation across beach ridges, which is important e.g. to reconstruct inundation distances, remains a major challenge. A primary tool for establishing a precisely confined correlation of the sand sheets is the use of chronological data. Since the application of radiocarbon dating is limited by the scarcity of appropriate material, this study utilised optically stimulated luminescence (OSL) dating of tsunamigenic quartz grains. Generally, the sediments showed favourable luminescence properties regarding signal intensity, dose recovery and thermal stability. Disturbances of the OSL signal due to partial bleaching were corrected using the minimum age model. At least three palaeoevents-being 490-550, 925-1035 and 1740-2000 yr old-were distinguished by dating the discontinuous sand sheets at four different sites. Besides this chronological framework, the OSL data provide the opportunity to correlate the discontinuous sand sheets between spatially separated sites within the same swale as well as across ridges. This allows for first estimates of inundation distances for the palaeotsunamis documented on Phra Thong Island. Furthermore, the two younger events overlap in age with contemporaneous tsunami and earthquake evidence from other coasts bordering the Indian Ocean.

We model postseismic changes to the shoreline of West Aceh, Indonesia, a region largely affected by the December 2004 Sumatra-Andaman earthquake and ensuing Indian Ocean tsunami, using a crossshore morphodynamic model. Subsidence of 0.5-1.0 m and tsunami scouring during the 2004 event caused the complete destruction of the beach and the landward displacement of the western coast of Aceh by an average of 110 m. Comparing a series of satellite images and topographic surveys, we reconstruct the build-up of a new beach ridge along a 6 km long stretch of coastline in the years following the event. We then use the cross-shore model UNIBEST-TC developed for a wave-dominated sandy shoreline to determine the controlling factors of shoreline recovery. Input parameters include bathymetric data measured in 2015, grain size characteristics of offshore sediment samples, modeled wave data, tidal elevations from a nearby tide-gauge station as well as measured and modeled postseismic uplift data. After establishing a cross-shore profile in equilibrium with the prevailing hydrodynamic conditions, we

The 26 th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past.

The 26 th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified ...

The Chilean tsunami of 22 May 1960 reamed out a breach and built up a fan as it flowed across a sparsely inhabited beach-ridge plain near Maullín, midway along the length of the tsunami source. Eyewitnesses to the flooding, interviewed mainly in 1988 and 1989, identified levels that the tsunami had reached on high ground, trees, and buildings. The maximum levels fell, from about 10 m to 2 m, between the mouth of the tidal Río Maullín and an inundation limit nearly 5 km inland across the plain. Along this profile at Caulle, where the maximum flow depth was a few meters deep, airphotos taken in 1961 show breaches across a road on a sandy beach ridge. Inland from one of these breaches is a fan with branched distributaries. Today its breach holds a pond that has been changing into a marsh. The 1960 fan deposits, as much as 60 cm thick, are traceable inland for 120 m from the breach. They rest on a pasture soil above two additional sand bodies, each atop its own buried soil. The earlier of the pre-1960 sand bodies probably dates to AD 1270-1400, in which case its age is not statistically different from that of a sand sheet previously dated elsewhere near Maullín. The breach likely originated then and has been freshened twice. Evidence that the breach was freshened in 1960 includes a near-basal interval of cobble-size clasts of sediment and soil, most of them probably derived from the organic fill of pre-1960 breach. The cobbly interval is overlain by sand with ripple-drift laminae that record landward flow. The fan of another breach near Maullín, at Chanhué, also provides stratigraphic evidence for recurrent tsunamis, though not necessarily for the repeated use of the breach. These findings were anticipated a half century ago by description of paired breaches and fans that the 1960 Chilean tsunami produced in Japan. Breaches and their fans may provide lasting evidence for tsunami inundation of beach-ridge plains. The breaches might be detectable by remote sensing, and the thickness of the fan deposits might help them outlast an ordinary tsunami sand sheet.

When dealing with fine-grained, organic-rich, colour-monotone, underwater marine sediment cores retrieved from the continental shelf or slope, the initial visual impression, upon split-opening the vessels, is often of a "disappointing" homogeneous, monotonous, continuous archive. Only after thorough, microto macro-scale, multi-parameter investigations the sediment reveals its treasures, initially by performing some measurements on the intact core itself, hence depicting for the first time its contents, and subsequently by carrying out the destructive, multi-proxy sample-based analyses.

Nagapattinam, in the east coast of India, was severely affected during the deadliest Indian Ocean tsunami of December 26, 2004. The tsunami caused heavy damage to life and property, and the death toll was about 3,378 in Nagapattinam taluk. Certain villages along the coast witnessed large inundation while adjacent villages were protected from the fury of the tsunami waves. This study was carried out to examine the underlying causes for the vulnerability along Nagapattinam coast with the help of field observations, remote sensing, and geographical information system as tools. Coastal areas with high sand dunes have been protected from tsunami, and areas adjacent to backwaters were inundated. Realtime Kinematic Global Positioning System and high-resolution satellite data were used to map the topographic information and maximum extent of inundation. Thematic maps on land use, land cover, and coastal geomorphology were generated using remote sensing and field data. Using field data as the primary source of information, tsunami hazard maps have been generated for Nagapattinam. Keywords East coast of India Á Nagapattinam Á Tsunami Á Inundation Á Run-up Á Geomorphology Á Hazard Map 1 Introduction Nagapattinam district (Fig. 1) in India's eastern coast was one of the worst affected regions in mainland India due to the tsunami that hit the Indian coast with a magnitude of 9.3 M w on December 26, 2004. The Nagapattinam district has five taluks (subdivisions of a district) and supports a population of about 1,48,70,55. All the five coastal taluks of Nagapattinam district namely Nagapattinam, Keelvelur, Vedaranyam, Tarangambadi, and Sirkali were severely affected by the tsunami. The district has a large coastline of 140 km, and inland gradients indicate that most of the coastal areas have low coastal slope

The tsunami generated by the offshore Samos Island earthquake (Mw = 7.0, 30 October 2020) is the largest in the Aegean Sea since 1956 CE. Our study was based on field surveys, video records, eyewitness accounts and far-field mareograms. Sea recession was the leading motion in most sites implying wave generation from seismic dislocation. At an epicentral distance of ~12 km (site K4, north Samos), sea recession, followed by extreme wave height (h~3.35 m), occurred 2′ and 4′ after the earthquake, respectively. In K4, the main wave moved obliquely to the coast. These features may reflect coupling of the broadside tsunami with landslide generated tsunami at offshore K4. The generation of an on-shelf edge-wave might be an alternative. A few kilometers from K4, a wave height of ~1 m was measured in several sites, except Vathy bay (east, h = 2 m) and Karlovasi port (west, h = 1.80 m) where the wave amplified. In Vathy bay, two inundations arrived with a time difference of ~19′, the second b...

Optical dating of liquefied sand structures formed during major earthquakes in Upper Assam, northeast of India, has been carried out to constrain the timing of prehistoric earthquakes in this seismically active region. The bleaching of source material and of the same material during the creation of a liquefaction feature was tested using quartz extracted from 21 samples associated with two different liquefaction structures in Upper Assam. Due to the poor sensitivity of quartz from this region, a sensitisation procedure was used in our SAR protocol to reduce the scatter in optical ages. Various internal consistency tests of the measurement protocol and the excellent reproducibility of the OSL ages indicate that the dose estimates from the quartz are accurate and the optical ages reliable. The preliminary OSL ages indicate that the liquefaction features were formed between 1430 AD and 1630 AD. This study demonstrates that using OSL, 'direct dating' of prehistoric earthquakes may be possible, if sand blows from liquefied dykes are preserved.

In August 2005, a team surveyed the effects of the December 2004 Indian Ocean tsunami on the southern coast of Oman. Runup and inundation were obtained at 41 sites, extending over a total of 750 km of shoreline. Measured runup ranged from 3.25 m in the vicinity of Salalah to a negligible value at one location on Masirah Island. In general, the largest values were found in the western part of the surveyed area. Significant incidents were documented in the port of Salalah, where a 285-m-long vessel broke its moorings and drifted inside and outside the port, and another ship struck the breakwater while attempting to enter the harbor. The general hazard to Oman from tsunamis may be greatest from the neighboring Makran subduction zone in western Pakistan.

The tsunami generated by the offshore Samos Island earthquake (Mw = 7.0, 30 October 2020) is the largest in the Aegean Sea since 1956 CE. Our study was based on field surveys, video records, eyewitness accounts and far-field mareograms. Sea recession was the leading motion in most sites implying wave generation from seismic dislocation. At an epicentral distance of ~12 km (site K4, north Samos), sea recession, followed by extreme wave height (h~3.35 m), occurred 2′ and 4′ after the earthquake, respectively. In K4, the main wave moved obliquely to the coast. These features may reflect coupling of the broadside tsunami with landslide generated tsunami at offshore K4. The generation of an on-shelf edge-wave might be an alternative. A few kilometers from K4, a wave height of ~1 m was measured in several sites, except Vathy bay (east, h = 2 m) and Karlovasi port (west, h = 1.80 m) where the wave amplified. In Vathy bay, two inundations arrived with a time difference of ~19′, the second b...

As many as seven tsunamis from the past 8000 years are evidenced by sand sheets that rest on buried wetland soils at Badabalu, southern Andaman Island, along northern part of the fault rupture of the giant 2004 Aceh-Andaman earthquake. The uppermost of these deposits represents the 2004 tsunami. Underlying deposits likely correspond to historical tsunamis of 1881, 1762, and 1679 CE, and provide evidence for prehistoric tsunamis in 1300–1400 CE, in 2000–3000 and 3020–1780 BCE, and before 5600–5300 BCE. The sequence includes an unexplained hiatus of two or three millennia ending around 1400 CE, which could be attributed to accelerated erosion due to Relative Sea-Level (RSL) fall at ~3500 BP. A tsunami in 1300–1400, comparable to the one in 2004, was previously identified geologically on other Indian Ocean shores. The tsunamis assigned to 1679, 1762, and 1881, by contrast, were more nearly confined to the northeast Indian Ocean. Sources have not been determined for the three earliest o...

The 17 July 2006 magnitude Mw 7.8 earthquake off the south coast of western Java, Indonesia, generated a tsunami that effected over 300 km of coastline and killed more than 600 people, with locally focused runup heights exceeding 20 m. This slow earthquake was hardly felt on Java, and wind waves breaking masked any preceding withdrawal of the water from the shoreline, making this tsunami difficult to detect before impact. An International Tsunami Survey Team was deployed within one week and the investigation covered more than 600 km of coastline. Measured tsunami heights and run-up distributions were uniform at 5 to 7 m along 200 km of coast; however there was a pronounced peak on the south coast of Nusa Kambangan, where the tsunami impact carved a sharp trimline in a forest at elevations up to 21 m and 1 km inland. Local flow depth exceeded 8 m along the elevated coastal plain between the beach and the hill slope. We infer that the focused tsunami and runup heights on the island su...

The Chilean tsunami of 22 May 1960 reamed out a breach and built up a fan as it flowed across a sparsely inhabited beach-ridge plain near Maullín, midway along the length of the tsunami source. Eyewitnesses to the flooding, interviewed mainly in 1988 and 1989, identified levels that the tsunami had reached on high ground, trees, and buildings. The maximum levels fell, from about 10 m to 2 m, between the mouth of the tidal Río Maullín and an inundation limit nearly 5 km inland across the plain. Along this profile at Caulle, where the maximum flow depth was a few meters deep, airphotos taken in 1961 show breaches across a road on a sandy beach ridge. Inland from one of these breaches is a fan with branched distributaries. Today its breach holds a pond that has been changing into a marsh. The 1960 fan deposits, as much as 60 cm thick, are traceable inland for 120 m from the breach. They rest on a pasture soil above two additional sand bodies, each atop its own buried soil. The earlier of the pre-1960 sand bodies probably dates to AD 1270-1400, in which case its age is not statistically different from that of a sand sheet previously dated elsewhere near Maullín. The breach likely originated then and has been freshened twice. Evidence that the breach was freshened in 1960 includes a near-basal interval of cobble-size clasts of sediment and soil, most of them probably derived from the organic fill of pre-1960 breach. The cobbly interval is overlain by sand with ripple-drift laminae that record landward flow. The fan of another breach near Maullín, at Chanhué, also provides stratigraphic evidence for recurrent tsunamis, though not necessarily for the repeated use of the breach. These findings were anticipated a half century ago by description of paired breaches and fans that the 1960 Chilean tsunami produced in Japan. Breaches and their fans may provide lasting evidence for tsunami inundation of beach-ridge plains. The breaches might be detectable by remote sensing, and the thickness of the fan deposits might help them outlast an ordinary tsunami sand sheet.

As many as seven tsunamis from the past 8000 years are evidenced by sand sheets that rest on buried wetland soils at Badabalu, southern Andaman Island, along northern part of the fault rupture of the giant 2004 Aceh-Andaman earthquake. The uppermost of these deposits represents the 2004 tsunami. Underlying deposits likely correspond to historical tsunamis of 1881, 1762, and 1679 CE, and provide evidence for prehistoric tsunamis in 1300–1400 CE, in 2000–3000 and 3020–1780 BCE, and before 5600–5300 BCE. The sequence includes an unexplained hiatus of two or three millennia ending around 1400 CE, which could be attributed to accelerated erosion due to Relative Sea-Level (RSL) fall at ~3500 BP. A tsunami in 1300–1400, comparable to the one in 2004, was previously identified geologically on other Indian Ocean shores. The tsunamis assigned to 1679, 1762, and 1881, by contrast, were more nearly confined to the northeast Indian Ocean. Sources have not been determined for the three earliest o...

The 26 th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified ...

The December 2004 Sumatra-Andaman tsunami prompted an unprecedented research effort to find ancient precursors and quantify the recurrence time of such a deadly natural disaster. This effort, however, has focused primarily along the northern and eastern Indian Ocean coastlines, in proximal areas hardest hit by the tsunami. No studies have been made to quantify the recurrence of tsunamis along the coastlines of the western Indian Ocean, leading to an underestimation of the tsunami risk in East Africa. Here, we document a 1000-yr-old sand layer hosting archaeological remains of an ancient coastal Swahili settlement in Tanzania. The sedimentary facies, grain-size distribution, and faunal assemblages indicate a tsunami wave as the most likely cause for the deposition of this sand layer. The tsunami in Tanzania is coeval with analogous deposits discovered at eastern Indian Ocean coastal sites. Numerical simulations of tsunami wave propagation indicate a megathrust earthquake generated by...

In August 2005, a team surveyed the effects of the December 2004 Indian Ocean tsunami on the southern coast of Oman. Runup and inundation were obtained at 41 sites, extending over a total of 750 km of shoreline. Measured runup ranged from 3.25 m in the vicinity of Salalah to a negligible value at one location on Masirah Island. In general, the largest values were found in the western part of the surveyed area. Significant incidents were documented in the port of Salalah, where a 285-m-long vessel broke its moorings and drifted inside and outside the port, and another ship struck the breakwater while attempting to enter the harbor. The general hazard to Oman from tsunamis may be greatest from the neighboring Makran subduction zone in western Pakistan.

for facilities and encouragement. Faculty and staff members of IHBT herbarium are thanked for guidance and fruitful discussions. The State Forest Department, Himachal Pradesh is acknowledged for help and support. Department of Biotechnology, New Delhi is thanked for financial support. We acknowledge the constructive comments by two anonymous reviewers which helped in improving the manuscript. This is IHBT communication number 540.

An examination of the coastal geomorphology of bays along the Otago coastline, SE New Zealand, has identified a geomorphology consistent with tsunami inundation. A tsunami geomorphology consisting of a number of elements including dune pedestals, hummocky topography, parabolic dune systems, and post-tsunami features resulting from changes to the nearshore sediment budget is discussed. The most prominent features at Blueskin Bay are eroded pedestals although it is speculated that hummocky topography may be present in the bay. Tsunami geomorphology at Long Beach is more comprehensive with a marked association between pedestals and a hummocky topography. A full suite of potential geomorphological features however, is not present at either site. The type of features formed by a tsunami, and the ability to detect and interpret a tsunami geomorphology, hinges on the interaction between five key variables; sand availability, embayment type, nature of the coast, accumulation space, and landward environmental conditions. An appreciation of the geomorphic setting and history of a coast is therefore of fundamental importance when identifying what to look for and where to look for tsunami evidence. It is also important to realise that these features can also be formed by other processes.

for facilities and encouragement. Faculty and staff members of IHBT herbarium are thanked for guidance and fruitful discussions. The State Forest Department, Himachal Pradesh is acknowledged for help and support. Department of Biotechnology, New Delhi is thanked for financial support. We acknowledge the constructive comments by two anonymous reviewers which helped in improving the manuscript. This is IHBT communication number 540.

Stratigraphic records from west coast of South Andaman Island revealed evidence of three historical earthquakes and associated transoceanic tsunamis during past 1000 yrs, in addition to the Mw 9.3 tsunamigenic earthquake of 26 December, 2004. Our finding suggests that along with Sumatran arc segment the Andaman-Arakan segment is also capable of generating mega-subduction zone earthquakes and transoceanic tsunamis. To study the near sub-surface stratigraphic succession we excavated shallow trenches and obtained geoslices from two sites around Collinpur (sites 1 and 2). The exposed succession comprised 11 lithounits (Unit a -youngest and k -oldest) of alternating sequence of coarser units overlain by peaty soils and some of these are indicative of deposition during paleo-tsunami events. Event I that predated AD 800, and is marked by a 35-40 cm thick deposit of fine gravel to coarse sands along with broken shell fragments (Unit k). Event II dated around AD 660-800, is represented by 20-25 cm thick coarse sand and broken shell fragments (Unit i). Based on stratigraphic evidences of land-level changes, this event is attributed to a near source rupture along Andaman-Arakan segment, accompanied by a transoceanic tsunami. Event III, occurred around AD 1120-1300, is marked by a 50 cm thick sand deposit (Unit g). The 2004 tsunami resulted in deposition of 15 cm thick medium to coarse sand at the same location. We infer that the 2004 tsunami and Event III resulted in different styles of sedimentation at the same site. Four events at Collinpur along with the record of a subsidence event of AD 1679 from the east coast of Andaman, close-to, Port Blair (Malik et al., 2011), suggest that mega-subduction zone earthquakes and associated tsunamis recur at an interval of 300-500 years at variable locations along the Sumatra-Andaman subduction zone.

Literature of the ancient Chola Dynasty (A.D. 9th-11th centuries) of South India and recent archaeological excavations allude to a sea flood that crippled the ancient port at Kaveripattinam, a trading hub for Southeast Asia, and probably affected the entire South Indian coast, analogous to the 2004 Indian Ocean tsunami impact. We present sedimentary evidence from an archaeological site to validate the textual references to this early medieval event. A sandy layer showing bed forms representing high-energy conditions, possibly generated by a seaborne wave, was identified at the Kaveripattinam coast of Tamil Nadu, South India. Its sedimentary characteristics include hummocky cross-stratification, convolute lamination with heavy minerals, rip-up clasts, an erosional contact with the underlying mud bed, and a landward thinning geometry. Admixed with 1000-year-old Chola period artifacts, it provided an optically stimulated luminescence age of 1091 Ϯ 66 yr and a thermoluminescence age of 993 Ϯ 73 yr for the embedded pottery sherds. The dates of these proxies converge around 1000 yr B.P., correlative of an ancient tsunami reported from elsewhere along the Indian Ocean coasts. * Thermoluminescence (TL) procedures used in the analyses are after Aitken (1985). TL and optically stimulated luminescence (OSL) were measured with RisoTL/OSL (model TL DA-15) reader. The dose rate was determined on the basis of assaying Th, U, and K by XRF analyses of the bulk samples. Standard laboratory procedures were followed to extract quartz from the 90-125-mm size fraction. The extracted quartz grains were etched for 80 minutes in hydrofluoric acid (40%) to remove the 10-mm layer (the HF treatment also removes any feldspar contamination). The water content was determined for all the samples by heating at 100°C. TL/OSL ages back calculated from A.D. 2006. The single aliquot regeneration protocol was used for equivalent dose (ED) determination .