Paleotsunami Deposits Research Articles

Tracing the sources of paleotsunamis using Bayesian frameworks

Paleotsunami deposits provide a compelling record of these events, including valuable insights into their recurrence and associated magnitudes. However, precisely determining the sources of these sedimentary evidence remains challenging due to the complex interplay between hydrodynamic and geological phenomena and the intricacy of the processes responsible for forming and preserving tsunami deposits. Here, we introduce a novel approach that employs Bayesian inference methods to divide the complex tsunami process into segments and independently handle uncertainties, thereby enabling more precise and comprehensive modelling of the sources. We provide a list of potential earthquake scenarios with different likelihoods instead of a single best fit. Based on this method, we calculated that the source of the 869 Jogan earthquake had a magnitude ranging from Moment Magnitude 8.84 to 9.1 (within one standard deviation) with different slip distributions along the Japan Trench. Our results reaffirm that the Jogan event had a similar order of magnitude to the 2011 Tohoku-oki tsunami and enhanced the applicability of paleotsunami deposits to hazard assessment.

Characterization of paleotsunami deposits along the western coast of India

Characterization of paleotsunami deposits along the western coast of India

Tsunami Modeling Study in Geological Disaster Mitigation in the Kwandang Region

The northern coast of the northern arm of Sulawesi is the meeting place of 3 plates that collided with each other during the Neogene period. This condition makes the northern part of Gorontalo, especially Kwandang sub-district, very prone to earthquakes with magnitudes above 6 on the Richter scale (SR), which is one of the triggers for tsunamis. In the period from 1990 - 2008, there were 4 major earthquakes recorded in Gorontalo, namely 1990 (7.3 SR), 1991 (7.1 SR), 1997 (7.0 SR) and 2008 (7.7 SR). Therefore, further research is needed on the return period of the earthquake and the tsunami model that occurs and the sign of tsunami occurrence in the past. This research aims to determine the return period of the earthquake that caused the tsunami and the tsunami model as well as the sedimentology analysis of paleotsunami deposits. The calculation of the earthquake return period uses the Guttenberg-Richter method. Modeling calculations were carried out using the COMCOT numerical model. This model performs calculations by solving shallow water equations in the form of both linear and non-linear equations. Paleotsunami deposits were analyzed using the sedimentology method. The results of the calculation at a magnitude of 6.0 SR show that within 100 years, the study area has a chance of a potentially destructive earthquake of 1.14024978. The results of modeling the tsunami-prone zone, obtained an area of 165.598389 ha. And obtained paleotsunami deposits containing foraminifera with a sediment thickness of 14 cm.

GRANULOMETRIC ANALYSIS OF PALEOTSUNAMI DEPOSITS CANDIDATE IN TERNATE ISLAND, NORTH MALUKU

Ternate Island is a volcanic island located in the Maluku Sea. Tsunami ever hit Ternate before 1900 or occurred before the age of the people living in this island. The paleotsunami suspect have been found in the western coast of Ternate Island. The outcrop has 50 m length and 1 m width, was discovered beneath the Gamalama eruption product which occurred in 1907. The paleotsunami candidate consists of at least five layers originating from different tsunami events. The granulometric analysis was carried out for each layer. The results obtained were that paleotsunami sediments had poorly sorted which indicated that the grain sizes were mixed, this was due to the energy of tsunami wave varied in time when transporting and depositing the sediments. Skewness varies from very fine to very coarse, indicating a change in the energy of the tsunami wave that occurs from very high when rising inland to decreasing as it returns to sea. Kurtosis varies from leptokurtic, platykurtic, and mesokurtic. Variations in mean, sorting, skewness and kurtosis values indicate a change in tsunami wave energy which causes a change in grain size. The granulometric analysis shows that the deposition of the youngest paleotsunami deposits candidate was initiated by a very strong current with the greatest energy, thus depositing very coarse sand to gravel, followed by a gradual decrease in energy and the tsunami wave process began to reverse towards the sea, then receded with the lowest energy and deposited finer grains. The sediment sources come from two different places, this shows that the sources come from the sea and the coast around the deposited paleotsunami candidates.

Identification of candidate paleotsunami deposit from sediment layers drilled in Seubadeh located in South Aceh of Indonesia

This study is conducted to identify prehistoric tsunami deposit (paleotsunami) in Seubadeh village, located in South Aceh Regency, Aceh province, Indonesia. Regional morphologic and seismic characteristics suggest that Seubadeh village is an area that stores tsunami deposits, both new tsunami deposits and prehistoric tsunami deposits. Therefore, in this study, the search for paleotsunami deposits was carried out in Seubadeh village. The tsunami deposit samples were taken at several points in Seubadeh village using a hand drill with a depth of more than 2 m. Sediment classification of the collected samples using Troels-Smith method shows a candidate layer of paleotsunami tsunami deposit was found between two clay deposits. The layer is dominated by plant roots and shell material. In addition, the sediment samples were sieved using a mesh to evaluate the grain size distribution of clay, silt and sand. The results of the grain size distribution and color evaluation of the respective layer are presented. The results of the analysis of the particle size distribution in the sample and the color of the sample indicate that there are 2 layers that show characteristics as a paleotsunami deposit, namely at a depth of about 170-200 cm and 280-292 cm. The paleotsunami deposit found will be further characterized by an emission spectroscopic technique.

Determination of Paleotsunami Inundation Zone Using Finite Difference Method in Southern Coastal Lebak, Banten

Paleotsunami deposits have been found in Indonesia, including in Pacitan, Kulon Progo, Cilacap, Pangandaran, and Sukabumi. This research aims to obtain an ideal model for determining the paleotsunami inundation zone along the southern coastal Lebak, Banten using finite difference numerical modeling through the MOST (Method of Splitting Tsunamis)-based ComMIT software. Field observations were made to identify the presence of paleotsunami deposits in the swale area on the southern coastal Lebak, Banten. Several tsunami scenarios such as Pangandaran in 2006, Indian Ocean Tsunami (IOT) in 2004, Tohoku in 2011, Sunda Strait megathrust segment, and megathrust along the south of Java were used in the modeling process to identify the characteristics of paleotsunami that were produced the tsunami deposits in the study area. Modeling is carried out using two schemes, such as using the ComMIT database unit source (subduction zone segments) and using the earthquake source parameters that are entered manually. The results show the best tsunami scenario that may have ever occurred in research area is the tsunami event with magnitude of 9.1 Mw, with maximum inundation range of 5.2 km, and run-off of up to 32 m, which is estimated as a tsunami event that precipates paleotsunami deposits in study area.

Impact of tourism gentrification on Megathrust Disaster Risk in Pacitan Regency

Pacitan Regency is one of the areas that has become the centre for the development of beach tourism in the southern region of Java Island. However, Pacitan is also a disaster-prone area, especially for earthquakes and tsunamis. The Pacitan area, in terms of geological conditions, is an area that has the potential to be affected by the threat of earthquakes, both centred at sea (subduction zones) and on land in the form of active faults. Pacitan Regency has the potential for a megathrust earthquake of 8.8, which can trigger a tsunami as high as 20 meters on land. The cycle of significant earthquakes and tsunamis originating from the subduction zone in southern Java occurs over a long time, where earthquakes are a repeating cycle that has the potential to happen in the future. Evidence related to past geological disasters from the south of Java is paleotsunami deposits in several places on the south coast of Java. Remains of tsunami deposits were found in Lebak (Banten), Pangandaran (West Java), Cilacap (Central Java) and Yogyakarta, to Pacitan (East Java). This study aims to (1) determine the level of vulnerability of the coastal tourism area of Pacitan Regency, (2) determine the level of social, cultural and economic capabilities of coastal communities and the government of Pacitan Regency, (3) develop the resilience of coastal communities and tourism communities to tsunamis and earthquakes. Megathrust in Pacitan Regency. Data collection was carried out by (1) field observations and measurements, (2) in-depth interviews with the community (3) secondary data collection. Data analysis used is spatial approach analysis, Geographic Information System (GIS) analysis, and hierarchy analysis. The study results show that Pacitan Regency is one of the fastest-growing districts. Tourism gentrification is one of the triggers for the increase in the gentrification process, which harms the megathrust disaster risk in Pacitan Regency.

Sedimentary diversity of the 2011 Tohoku-oki tsunami deposits on the Sendai coastal plain and the northern coast of Fukushima Prefecture, Japan

This paper documents the sedimentary characteristics of the widespread deposits associated with the 2011 Tohoku-oki tsunami on the lowlands along the Pacific coast of the Sendai and Fukushima regions, northern Japan, and observed tsunami inundation depths. In eight areas of the region, field observation was carried out at a total of 123 locations and sampling at a total of 49 locations. Grain-size analysis and soft X-ray imaging reveal that the tsunami deposits are usually composed of sheetlike sandy beds and generally show landward-thinning and landward-fining trends and a landward increase in mud content, although site-specific distributional patterns are apparent along each transect. These thickness and grain-size patterns indicate a landward decrease in flow capacity. This information on the sedimentology of tsunami deposits and observed inundation depths will assist with the identification of paleo-tsunami deposits in the geological record and provide valuable constraints for mathematical analyses of tsunami hydraulic conditions related to sedimentary characteristics.

Application of mineralogy and geochemistry to identify the landward extent of paleo-tsunami deposits not visible to the naked eye in the coastal wetland of Erimo, Hokkaido, Japan

Application of mineralogy and geochemistry to identify the landward extent of paleo-tsunami deposits not visible to the naked eye in the coastal wetland of Erimo, Hokkaido, Japan

Sedimentological observations and geochemical characteristics of paleo-tsunami deposits along the east coast of Sri Lanka in the Indian Ocean

The 2004 Indian Ocean tsunami caused 230,000 fatalities and massive physical damage along the shorelines of the Indian Ocean. Holocene sedimentary archives along the coastline of Sri Lanka can provide evidence for similar past events. The objective of our current study is to investigate the sedimentological and geochemical characteristics of Sri Lankan paleo-tsunami deposits, and their chronology. Sediment samples were collected down to 10 m depth using core drilling at a sheltered site (low-lying swale depression) in Koddiyar Bay (Trincomalee) on the east coast of Sri Lanka. Visual stratigraphic observations and grain size analyses were carried out to identify lithological changes. Bulk sediments, shells, and wood fragments were used for 14C age dating. Seven sand layers were identified throughout the core in this marshy wetland. Sedimentological observations and geomorphological features show that sheltered/protected swales of the inner bay have a high potential for preservation of paleo-tsunami sediments. Three possible paleo-tsunami deposits were identified earlier than 700 years, ca. 2000 years, and ca. 2700 years. These paleo-tsunami sand layers exhibited relatively high total organic carbon (TOC) contents due to admixture of continental shelf and lagoon sediments. Analysis of paleo-tsunami records suggests that the Andaman Sea is vulnerable to both ‘low-risk and high-frequency’ and ‘high-risk and low-frequency’ type tsunamis, whereas other areas in the Indian Ocean are more prone to destructive and low-frequency type tsunamis. This study contributes to improving tsunami risk assessment and mitigation strategies along the east coast of Sri Lanka.

Numerical estimation of a tsunami source at the flexural area of Kuril and Japan Trenches in the fifteenth to seventeenth century based on paleotsunami deposit distributions in northern Japan

Paleotsunami deposit investigations and numerical tsunami computations have been performed to elucidate the source and size of large tsunamis along the Kuril to Japan Trenches, particularly for unusual tsunamis that occurred in the seventeenth century, the 1611 CE Keicho tsunami (M 8.1) along the Japan Trench and seventeenth-century tsunami (> Mw 8.8) along the Kuril Trench, which caused serious damages on the coastal residents and environments. Moreover, several paleotsunami deposits dating from the thirteenth to eighteenth centuries have been reported along the area between the Kuril and Japan subduction zones, but their sources have not been clarified. In this study, we estimated the tsunami sources from numerical simulations using the distribution of fifteenth- to seventeenth-century tsunami deposits at Sekinehama along the coast of the Shimokita Peninsula. Based on numerical simulations with previously proposed fault models, the tsunami deposits showing similar ages at Sekinehama and another site on the coast of Shimokita Peninsula, which are within 50 km apart, could not be explained except with the huge earthquake models (> Mw 9.1), whose rupture zones extend to not only the Kuril or Japan Trenches but also their flexural area. Thus, we modified or newly proposed twelve fault models located in the flexural area between the two trenches to explain tsunami deposits possibly around the seventeenth century at the above-mentioned two sites on the coast of Shimokita Peninsula. Simulations using these models elucidated that the rupture in the shallow or deep plate boundaries with > 14–32 m slip (> Mw 8.55–8.76) is necessary. If the tsunami deposits around the seventeenth century along the Iburi–Hidaka coast in Hokkaido and those at the two sites mentioned above might be left by an identical event, an interplate earthquake with > 18–40 m slip (> Mw 8.62–9.2) in the flexural area is needed. Moreover, this interplate earthquake might have occurred in the deep plate boundary than in the shallower plate boundary based on slip deficit and slow earthquake distribution data. Our results offer significant insights into a large earthquake (> M 8) along the Kuril and Japan Trenches in the fifteenth to seventeenth century.

Assessing the validity of proposed paleo-tsunami deposits in Sweden

Until recently, the offshore effects of modern tsunamis were unknown. It is only within the past fifteen years that studies have started to examine the sedimentologic and stratigraphic signatures of modern tsunamis in the marine environment. Claims of paleo-tsunami deposits in Sweden, however, predate any knowledge of the offshore effects of tsunamis by more than ten years. These claims are based on lacustrine sediment sequences that would have been at outer shelf water depths during the proposed tsunamis. While numerous claims of paleo-tsunami deposits exist in Sweden, relatively few of these claims are reported in the peer-reviewed literature.The current study re-examines proposed paleo-tsunamis from Stockholm, Iggesund, and northern Uppland and points out a lack of critical geographical, stratigraphical, and chronological data. Additionally, consideration of the Holocene stratigraphy of these locations in the context of what is now known about the effects of tsunamis in the offshore environment indicates that there is currently no credible evidence of paleo-tsunamis in Sweden.

Paleotsunami history of Hachinohe, northern Japan: a multiproxy analysis and numerical modeling approach

Paleotsunami studies along the Pacific coast of Tohoku, northern Japan, have been considerably developed recently, particularly after the massive impact of the 2011 Tohoku-oki tsunami. Nevertheless, in the southernmost Shimokita Peninsula, studies pertaining to paleotsunami are underdeveloped, leading to a vague understanding of the tsunamigenic sources northward of the Tohoku region, along with incomplete hazard evaluation. Paleotsunami deposits in Shimokita can be related not only to the Japan Trench along the Sanriku coast but also to the Kuril trench along the Pacific coast of Hokkaido. In this study, we unveiled the paleotsunami history of Hachinohe in northern Tohoku. Using a combination of sedimentological, geochemical, paleontological, and mineralogical proxies, we characterized seven sand layers that dated from ca. 2700 to ca. 5500 yr BP based on radiocarbon (14C) ages as event deposits of marine origin. Sedimentological and paleontological evidence coupled with ground-penetrating radar imagery revealed a marsh environment comprising successive extinct ponds, controlling the depositional environment. Numerical modeling ruled out the possibility of storms as genetic sources, leading to the conclusion that the presence of event deposits with marine sediments in the study area would be associated with tsunami inundation episodes. Based on 14C dating, the mean frequency of recurrence of tsunamis is estimated as 384 years (320–450 yr, 95% confidence interval) and a coefficient of variation of 0.78 (0.68–0.99, 95% confidence interval). The previously recorded limited paleotsunami evidence and absence of an estimated recurrence interval in the Shimokita Peninsula reaffirm the importance of Hachinohe as a tsunami record site for the activity of both trenches.

An extended, 2.4-ka long record of western Pacific tsunamis and pumice rafts in northern Taiwan: Tsunami recurrence, pumice sources, and drifting routes

Encircled by arcs and trenches, the western Pacific region of the Philippine Sea is exposed to trans-oceanic tsunamis and pumice rafts. However, shortage of extended archive has limited our knowledge of tsunami recurrence, pumice sources, and drifting routes. This study identifies a backshore colluvium with three new pumice gravel layers in northern Taiwan, stratigraphically below four previously reported pumice-bearing paleotsunami deposits from the last millennium. The new layers are attributed to tsunamis, based on foreshore-derived sediments, facies characteristics reflecting suspension-rich turbulent flow process, supratidal locations exceeding typhoon surge heights, and mismatched super typhoon occurrences. The tsunami record therefore extends in duration from 1.0 to 2.4 ka with an increase in event number from four to seven, which unfolds new time intervals, stretches the recurrence from 100–400 to 100–800 years, and indicates complicated tsunami occurrences and sources in this region. Simultaneously, a stranded pumice archive is established by six of the seven paleotsunami deposits with abundant pumices rounded by grain-to-grain abrasion during drifting. The pumices consist of black, shoshonitic trachyte–trachyandesite grains and white, low-K dacite–rhyolite grains, indicating diverse sources and drifting routes. The unique alkali and adjoining subalkaline volcano provinces of the Izu-Bonin-Mariana Arc might have successively generated pumice rafts since 2.4 ka that embarked the Kuroshio counter and branch currents for northern Taiwan in a ∼2000-km-long course across the Philippine Sea. White rhyolite pumice domination is also present and comparable in composition to the southern Ryukyu pumice, indicating a ∼200 km-long northwest-bound route.

Mineralogy, geochemistry, and genesis of glauconite mineral from paleotsunami deposit in Lebak, Banten, Indonesia

Bagedur coast in Lebak regency, Banten province, Indonesia is part of lowland-swampy swale area that consist of various sediment deposit. Based on its sediment characteristics and geomorphology profile, Bagedur coast is assumed as depositional environment of paleotsunami deposit. Hand Auger drilling method is used to collecting loose sediment sample from eight observation stations. The depth of hand drilling in BG 01 station to BG 08 station is consecutively as follows: 115 cm, 100 cm, 80 cm, 700 cm, 400 cm, 450 cm, 160 cm, and 143 cm. This research is carried out to understand the diagenetic process of glauconite mineral in presumption paleotsunami deposit. The diagenetic process of glauconite mineral is identified based on its mineralogical and geochemical characteristics by petrography and X-Ray Fluorescence (XRF) methods. Observation samples is taken from green sand sediment bed in hand drilling core. Petrographic analysis under polarized microscope shows various glauconite mineral which recognized as matrix, oval pellets, replacement of precursor mineral, and bioclastic shell infillings. XRF analysis result show that glauconite in observation site are classified as glauconitic-illite type. The diagenetic stage is interpreted as early stage of diagenetic (nascent) which characterized by low Fe2O3 and K2O content relative to Al2O3 content.

Geochemical and heavy mineral signatures of marine incursions by a paleotsunami on the Miyazaki plain along the Nankai–Suruga trough, the Pacific coast of southwest Japan

Earthquakes and tsunami repeatedly occur in the coastal areas of the Japanese islands, which are located on the margin of continental plates. Paleotsunami deposits in these areas provide important clues regarding the reconstruction of past marine incursions by earthquakes and tsunami. The Miyazaki plain on the Pacific coast of southwest Japan along the Nankai–Suruga trough has been also affected by marine incursions by previous interplate earthquakes and tsunami. Tsunami deposits are usually identified by their geological, sedimentological, and geochemical characteristics. In the present work, portable energy dispersive X-ray fluorescence spectrometry (portable XRF), X-ray analytical microscopy (XGT), statistical analyses, and heavy mineral analyses were performed to characterize the paleotsunami deposits of the Kanbun Hyuganada earthquake (age, 1662 common era) in the SY03 core from the south Miyazaki plain. Our new findings can be summarized as follows: (1) Increases in the Ti-normalized values of S, Ca, Fe, and Sr, and depletions of K were observed in the deposits; (2) Accumulation of Zr and heavy minerals such as zircon, likely related with the high-energy tsunami, were found in the deposits; (3) Cluster analyses of the geochemical data acquired from the SY03 core by the portable XRF distinguished the paleotsunami deposits on the south Miyazaki plain. Furthermore, we also compiled the geochemical data of samples from the Shizuoka (central Japan), Sendai (Pacific coast of northeast Japan), and Miyazaki plains. Increases in Ti-normalized values (e.g., Sr/Ti) were found in these paleotsunami deposits. Our studies indicate that geochemical approaches are suitable for the characterization and exploration of paleotsunami deposits on the several coastal areas of Japan.

Identification of suspected paleotsunami deposits study from Karapyak Beach, Pangandaran area, West Jawa, Indonesia

Identifying and constraining palaeotsunami deposits can be a vital tool for establishing the periodicity of earthquakes and their associated tsunami events beyond the historical records. However, the deposits can be difficult to establish and date. In this study we used the characteristics of the 2006 Pangandaran tsunami deposit as a reference for identification of paleotsunami deposits in Karapyak Beach, Pangandaran area, West Java, Indonesia. Similar to the 2006 Pangandaran tsunami deposit, the Karapyak Beach paleotsunami deposit is characterized by light brown loose sand materials overlying a dark brown paleosoil layer with erosional contact. A thin layer that varies in thickness is locally found right above the erosional contact, with non-laminated coarser grain in the lower part that gradually change into medium to fine sand-sized in upper part. The base of the lower part is rich with broken mollusc shells and corals, and the mid-top of the lower part may contain several intact molusc shells and corals, rock fragments and anthropogenic products (rooftile). Those types of fragments are absent in the upper part of the thin layer. Grain size analysis shows a mixture of fine and coarse grains in the lower part of 2006 tsunami deposits as well as in the suspected paleotsunami deposits, suggesting uprush high energy flow during sedimentation. Fining upward sequence above mixed grain layers reflects waning flow or pre-backwash deposition. Foraminifera analysis also shows a mixture of shallow and deep marine foraminifera in the two deposits. Based on the characteristics of the 2006 tsunami deposits, there are at least four identified paleotsunami deposits at Karapyak Beach, Pangandaran area.

Using the paleotsunami data for the tsunami hazard assessment

The article is focused on the development of statistical methods of the tsunami recurrence evaluation using paleotsunami data. The new key moment is the creation of a model to quantify the preservation potential of paleotsunami deposits. The article includes a brief overview of the results of studies of the variability and preservation of tsunami deposits. The model was tested on materials about paleotsunami on the coast in the Khalaktyrka area (a village within the city of Petropavlovsk-Kamchatsky), obtained earlier, for four time intervals set by the key-marker volcanic tephra layers in Kamchatka (Ksudach in 1907, Avachinsky in 1855 and 1779, Opala in 606). The maximum likelihood estimates of the number of tsunamigenic horizons for the indicated time intervals are given. The restrictions of the considered model are analyzed.

Identification of Paleotsunami Deposits Using XRF and Artificial Intelligence Methods on the Southern Coast of Lebak, Banten

The southern coastal area of Lebak, Banten is the southern region of Java which is prone to tsunami disasters. There is evidence of past tsunami events in the southern region of Java. However, not all tsunami deposits have identifiable sedimentological and micropaleontological traces. Geochemical proxies and artificial intelligence with machine learning methods can be used to identify paleotsunami deposits. Machine learning methods that can be used to cluster paleotsunami deposits are Agglomerative Hierarchical Clustering (AHC) and Support Vector Machine (SVM) with validation of model accuracy using the Receiver Operating Characteristic (ROC) and Area Under Curve (AUC) methods. Input data are XRF analysis data and macroscopic core sample description data. The output from data processing is in the form of prediction of tsunami and non-tsunami deposits at each depth of core data sample. The data is correlated and interpreted to identify tsunami events that occurred in the past. The identification results show that the tsunami deposition in the research area, namely the area around the Bagedur coastal coast and Bolang village had tsunami deposit characteristics based on macroscopic description, XRF analysis, and artificial intelligence clusterization. It is also thought to be correlative with the tsunami deposition of previous research in the area around the Binuangeun coastal coast.

Indonesia paleotsunami database: Concept and design

Indonesia’s tectonic conditions are one of the regions in the world with the most active tectonic activity. As a result of these conditions, Indonesia is prone to earthquakes, tsunamis, and volcanic eruptions. Tsunamis are the most violent movements of ocean waves. The mechanism for tsunamis formation is through processes that generate shock waves, such as underwater earthquakes, underwater landslides, volcanic activity, and asteroid impacts. Indonesia has experienced a series of tsunami events that have caused thousands of casualties. Tsunami events are not fully recorded in human historical records. Unrecorded tsunami or paleotsunami events can be studied through the characteristics of paleotsunami deposits or related archaeological information about tsunamis. Knowing the history of tsunami events is essential to understand tsunamis frequency and intensity in the present. This study aims to conceptualize and design a historical database of tsunami occurrences in Indonesia. The database will be based on WebGIS. Tsunami event data is sourced from literature related to tsunami events, such as published books, journals, reports, final projects, and others. The results of database processing are 326 data on tsunami events in Indonesia. The WebGIS is an update for tsunami information media in Indonesia to be more comprehensive and informative.