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1.
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.  相似文献   

2.
In the aftermath of the 2004 Indian Ocean tsunami, a large increase in the activity of tsunami hazard and risk mapping is observed. Most of these are site-specific studies with detailed modelling of the run-up locally. However, fewer studies exist on the regional and global scale. Therefore, tsunamis have been omitted in previous global studies comparing different natural hazards. Here, we present a first global tsunami hazard and population exposure study. A key topic is the development of a simple and robust method for obtaining reasonable estimates of the maximum water level during tsunami inundation. This method is mainly based on plane wave linear hydrostatic transect simulations, and validation against results from a standard run-up model is given. The global hazard study is scenario based, focusing on tsunamis caused by megathrust earthquakes only, as the largest events will often contribute more to the risk than the smaller events. Tsunamis caused by non-seismic sources are omitted. Hazard maps are implemented by conducting a number of tsunami scenario simulations supplemented with findings from literature. The maps are further used to quantify the number of people exposed to tsunamis using the Landscan population data set. Because of the large geographical extents, quantifying the tsunami hazard assessment is focusing on overall trends.  相似文献   

3.
Little Andaman, the fourth largest island in the Andaman group of islands of India, was severely affected by the December 26, 2004, Indian Ocean tsunami generated by massive earthquake of moment magnitude 9.3 Mw which devastated the Andaman and Nicobar group of islands causing heavy damage to life and property. Due to hostile terrain conditions not much information was available on the extent of inundation and run-up along the island except for Hut Bay region. In order to study the vulnerability of the island to tsunami hazard, the inundation in the island due to the 2004 tsunami was studied using TUNAMI N2 numerical model and ENVISAT ASAR datasets. The extent of inundation derived from the SAR imagery was compared using the RTK-GPS field survey points collected in the Hut Bay regions immediately after the 2004 tsunami. The extent of inundation obtained from SAR images for the entire island was compared with inundation obtained from model. It was observed that the inundation obtained from the model matched well with inundation extent from SAR imagery for nearshore regions, while for low-lying areas and creeks large deviations were observed. In the absence of field datasets, the inundation derived from SAR imagery would be effective in providing ground data to validate the numerical models which can then be run for multiple scenarios for disaster mitigation and planning operation in areas that have hostile terrain conditions.  相似文献   

4.
The tsunami run-up, inundation and damage pattern observed along the coast of Tamilnadu (India) during the deadliest Indian Ocean tsunami of December 26, 2004 is documented in this paper. The tsunami caused severe damage and claimed many victims in the coastal areas of eleven countries, bordering the Indian Ocean. Along the coast of Indian mainland, the damage was caused by the tsunami only. Largest tsunami run-up and inundation was observed along the coast of Nagapattinam district and was about 10–12 m and 3.0 km, respectively. The measured inundation data were strongly scattered in direct relationship to the morphology of the seashore and the tsunami run-up. Lowest tsunami run-up and inundation was measured along the coast of Thanjavur, Puddukkotai and Ramnathpuram districts of Tamilnadu in the Palk Strait. The presence of shadow of Sri Lanka, the interferences of direct/receded waves with the reflected waves from Sri Lanka and Maldive Islands and variation in the width of continental shelf were the main cause of large variation in tsunami run-up along the coast of Tamilnadu.  相似文献   

5.
The M w = 9.1 mega-thrust Sumatra–Andaman earthquake that occurred on December 26, 2004, was followed by a devastating tsunami that killed hundreds of thousands of people and caused catastrophic effects on human settlements and environments along many coasts of the Indian Ocean, where even countries very far from the source were affected. One of these cases is represented by the Republic of Seychelles, where the tsunami reached the region about 7 h after the earthquake and produced relevant damages, despite the country was more than 4,500 km far from the seismic source. In the present work, we present and discuss a study of the 2004 Sumatra tsunami by means of numerical simulations with the attention focused on the effects observed at the Seychelles Archipelago, a region never previously investigated with this approach. The case is interesting since these islands lay on a very shallow oceanic platform with steep slopes so as the ocean depth changes from thousands to few tens of meters over short distances, with significant effects on the tsunami propagation features: the waves are strongly refracted by the oceanic platform and the tsunami signal is modified by the introduction of additional frequencies. The study is used also to validate the UBO-TSUFD numerical code on a real tsunami event in the far field, and the results are compared with the available observations, i.e., the sea level time series recorded at the Pointe La Rue station, Mahé Island, and run-up measurements and inundation lines surveyed few weeks after the tsunami at Praslin Island, where the tsunami hit during low tide. Synthetic results are found in good agreement with observations, even though some of the observations remain not fully solved. Moreover, simulations have been run in high-tide condition since the 2004 Sumatra tsunami hitting at high tide can be taken as the worst-case scenario for the Seychelles islands and used for tsunami hazard and risk assessments.  相似文献   

6.
Natural disasters can neither be predicted nor prevented. Urban areas with a high population density coupled with the construction of man-made structures are subjected to greater levels of risk to life and property in the event of natural hazards. One of the major and densely populated urban areas in the east coast of India is the city of Chennai (Madras), which was severely affected by the 2004 Tsunami, and mitigation efforts were severely dampened due to the non-availability of data on the vulnerability on the Chennai coast to tsunami hazard. Chennai is prone to coastal hazards and hence has hazard maps on its earth-quake prone areas, cyclone prone areas and flood prone areas but no information on areas vulnerable to tsunamis. Hence, mapping has to be done of the areas where the tsunami of December 2004 had directly hit and flooded the coastal areas in Chennai in order to develop tsunami vulnerability map for coastal Chennai. The objective of this study is to develop a GIS-based tsunami vulnerability map for Chennai by using a numerical model of tsunami propagation together with documented observations and field measurements of the evidence left behind by the tsunami in December 2004. World-renowned and the second-longest tourist beach in the world “Marina” present in this region witnessed maximum death toll due to its flat topography, resulting in an inundation of about 300 m landward with high flow velocity of the order of 2 m/s.  相似文献   

7.
This paper outlines the field measurements and numerical modelling carried out to develop a high-resolution tsunami inundation map, as a case study, for the city of Trincomalee on the east coast of Sri Lanka, which was devastated by the 2004 tsunami. We employ the deterministic approach together with numerical simulations based on the probable worst-case scenario to derive the inundation map. Linear and non-linear versions of shallow-water equations have been utilized to simulate tsunami propagation and onshore inundation, respectively. The field data considered in the present paper comprise the extent of inundation, the tsunami heights and the arrival times whilst the model results include the spatial distribution of the flow depth, the peak current speeds and the momentum flux. The computed extent of onshore inundation reproduces the observed overall pattern of inundation in most areas barring the south-eastern part of the city. Further, the model simulations suggest maximum flow depths up to about 2 m in most areas of the city whilst patches of flow depths exceeding 2 m can be seen in a narrow strip along the coastline. The computed current speeds also exceed 3 m/s at some locations adjacent to the shoreline.  相似文献   

8.
Following the devastating tsunami of 26 December 2004 in the Indian Ocean, there was a need to give a voice to the affected population. Hence a survey was conducted in the tsunami-affected regions of India. The tsunami mainly affected the states of Tamil Nadu, Kerala and Andhra Pradesh and the Union Territory of Pondicherry, all in south India, as well as the Andaman and Nicobar Islands of India in the Bay of Bengal. For various logistical reasons, no survey was conducted in the Andaman and Nicobar Islands. The survey was conducted during 21 January to 19 February 2005 and from 1 March to 8 March 2005. A total of eight people, arranged into four teams, simultaneously conducted the survey based upon a prepared questionnaire comprising a total of 16 questions. The total number of villages surveyed was 161, and the overall results of the survey are reported here. Among many observations, capacity building during the construction process, relocation and housing issues and tsunami education and awareness were prominent.  相似文献   

9.
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10.
Following the catastrophic “Great Sumatra–Andaman” earthquake- tsunami in the Indian Ocean on the 26th December 2004, questions have been asked about the frequency and magnitude of tsunami within the region. We present a summary of the previously published lists of Indian Ocean Tsunami (IOT) and the results of a preliminary search of archival materials held at the India Records Office, at the British Library in London. We demonstrate that in some cases, normal tidal movements and floods associated with tropical cyclones have been erroneously listed as tsunami. We summarise archival material for tsunami that occurred in 1945, 1941, 1881, 1819, 1762 and a little known tsunami in 1843. We present the results of modelling of the 2004, 1861 and 1833 tsunami generated by earthquakes off Sumatra and the 1945 Makran earthquake and tsunami, and examine how these results help to explain some of the historical observations. The highly directional component to tsunami propagation illustrated by the numerical models may explain why we are unable to locate archival records of the 1861 and 1833 tsunami at important locations like Rangoon, Kolkata (formally Calcutta) and Chennai (formally Madras), despite reports that these events created large tsunami that inundated western Sumatra. The numerical models identify other areas (particularly the central and southern Indian Ocean islands) where the 1833 tsunami may have had a large enough effect to produce a historic record. We recommend further archival research, coastal geological investigations of tsunami impacts and detailed modelling of tsunami propagation to better understand the record and effects of tsunami in the Indian Ocean and to estimate their likelihood of occurring in the future.  相似文献   

11.
The Indian Ocean Tsunami of December 2004 caused inundation of seawater along the Northern coast of Tamil Nadu, India, resulting in loss of 8,000 people with extensive damage to properties. The paper describes the inundation of seawater in two northern districts, namely Kancheepuram and Villupuram districts, which showed distinct patterns of inundation of seawater and run-up levels due to variations in geomorphic features. TUNAMI N2 model was used to predict the seawater inundation for earthquakes occurred in 1881 at Car Nicobar, Sumatra 2004 and a worst-case scenario. The coastal areas with beaches having gentle slope showed more inundation compared with coastal areas having varied slope and habited by sand dunes and coastal vegetation. Appreciable inundation of seawater with tsunami simulated for 1881 Car Nicobar indicated that proximity to the source plays a major role besides earthquake parameters in causing inundation. The worst-case scenario generated from subduction zone of Car Nicobar using Sumatra 2004 earthquake parameters revealed extreme vulnerability of coasts of both the districts to giant tsunamis.  相似文献   

12.
As seen in many of the satellite images from the tsunami in the Indian Ocean which struck in 2004, there is a distinctive limit between an area with sand coverage, vegetation destruction, and soil erosion on the one hand, and the unaffected natural vegetation on the other. This distinction provides a good landmark to map the inundation width, delimited on the landward side by a trimline. In this study, older trimlines, dating back about 300?years, from tsunamis that occurred throughout the world were documented. We discuss the origin and chronology of trimline modification and extinction, both of which depend on local topography, rock type, and climate.  相似文献   

13.
The Sultanate of Oman is among the Indian Ocean countries that were subjected to at least two confirmed tsunamis during the twentieth and twenty-first centuries: the 1945 tsunami due to an earthquake in the Makran subduction zone in the Sea of Oman (near-regional field tsunami) and the Indian Ocean tsunami in 2004, caused by an earthquake from the Andaman Sumatra subduction zone (far - field tsunami). In this paper, we present a probabilistic tsunami hazard assessment for the entire coast of Oman from tectonic sources generated along the Makran subduction zone. The tsunami hazard is assessed taking into account the contribution of small- and large-event magnitudes. Results of the earthquake recurrence rate studies and the tsunami numerical modeling for different magnitudes were used through a logic-tree to estimate the tsunami hazard probabilities. We derive probability hazard exceedance maps for the Omani coast considering the exposure times of 100, 250, 500, and 1000 years. The hazard maps consist of computing the likelihood that tsunami waves exceed a specific amplitude. We find that the probability that a maximum wave amplitude exceeds 1 m somewhere along the coast of Oman reaches, respectively, 0.7 and 0.85 for 100 and 250 exposure times, and it is up to 1 for 500 and 1000 years of exposure times. These probability values decrease significantly toward the southern coast of Oman where the tsunami impact, from the earthquakes generated at Makran subduction zone, is low.  相似文献   

14.
The Indian Ocean Tsunami of December 26, 2004 devastated coastal ecosystems across South Asia. Along the coastal regions of South India, increased groundwater levels (GWL), largely caused by saltwater intrusion, infiltration from inundated land, and disturbance of freshwater lenses, were reported. Many agencies allocated funding for restoration and rehabilitation projects. However, to streamline funding allocation efforts, district-level groundwater inundation/recession data would have been a useful tool for planners. Thus, to ensure better preparedness for future disaster relief operations, it is crucial to quantify pre- and post-tsunami groundwater levels across coastal districts in India. Since regional scale GWL field observations are not often available, this study instead used space gravimetry data from NASA’s Gravity Recovery and Climate Experiment (GRACE), along with soil moisture data from the Global Land Data Assimilation Systems (GLDAS), to quantify GWL fluctuations caused by the tsunami. A time-series analysis of equivalent groundwater thickness was developed for February 2004–December 2005 and the results indicated a net increase of 274 % in GWLs along coastal regions in Tamil Nadu following the tsunami. The net recharge volume of groundwater due to the tsunami was 16.8 km3, just 15 % lower than the total annual groundwater recharge (19.8 km3) for the state of Tamil Nadu. Additionally, GWLs returned to average within 3 months following the tsunami. The analysis demonstrated the utility of remotely sensed data in predicting and assessing the impacts of natural disasters.  相似文献   

15.
The 2004 tsunami that struck the Sumatra coast gave a warning sign to Malaysia that it is no longer regarded as safe from a future tsunami attack. Since the event, the Malaysian Government has formulated its plan of action by developing an integrated tsunami vulnerability assessment technique to determine the vulnerability levels of each sector along the 520-km-long coastline of the north-west coast of Peninsular Malaysia. The scope of assessment is focused on the vulnerability of the physical characteristics of the coastal area, and the vulnerability of the built environment in the area that includes building structures and infrastructures. The assessment was conducted in three distinct stages which stretched across from a macro-scale assessment to several local-scale and finally a micro-scale assessment. On a macro-scale assessment, Tsunami Impact Classification Maps were constructed based on the results of the tsunami propagation modelling of the various tsunami source scenarios. At this stage, highly impacted areas were selected for an assessment of the local hazards in the form of local flood maps based on the inundation modelling output. Tsunami heights and flood depths obtained from these maps were then used to produce the Tsunami Physical Vulnerability Index (PVI) maps. These maps recognize sectors within the selected areas that are highly vulnerable to a maximum tsunami run-up and flood event. The final stage is the development of the Structural Vulnerability Index (SVI) maps, which may qualitatively and quantitatively capture the physical and economic resources that are in the tsunami inundation zone during the worst-case scenario event. The results of the assessment in the form of GIS-based Tsunami-prone Vulnerability Index (PVI and SVI) maps are able to differentiate between the various levels of vulnerability, based on the tsunami height and inundation, the various levels of impact severity towards existing building structures, property and land use, and also indicate the resources and human settlements within the study area. Most importantly, the maps could help planners to establish a zoning scheme for potential coastline development based on its sensitivity to tsunami. As a result, some recommendations on evacuation routes and tsunami shelters in the potentially affected areas were also proposed to the Government as a tool for relief agencies to plan for safe evacuation.  相似文献   

16.
Coastal communities in the western United States face risks of inundation by distant tsunamis that propagate across the Pacific Ocean as well as local tsunamis produced by great (Mw?>?8) earthquakes on the Cascadia subduction zone. In 1964, the Mw 9.2 Alaska earthquake launched a Pacific-wide tsunami that flooded Cannon Beach, a small community (population 1640) in northwestern Oregon, causing over $230,000 in damages. However, since the giant 2004 Indian Ocean tsunami, the 2010 Chile tsunami and the recent 2011 Tohoku-Oki tsunami, renewed concern over potential impacts of a Cascadia tsunami on the western US has motivated closer examination of the local hazard. This study applies a simple sediment transport model to reconstruct the flow speed of the most recent Cascadia tsunami that flooded the region in 1700 using the thickness and grain size of sand layers deposited by the waves. Sedimentary properties of sand from the 1700 tsunami deposit provide model inputs. The sediment transport model calculates tsunami flow speed from the shear velocity required to suspend the quantity and grain size distribution of the observed sand layers. The model assumes a steady, spatially uniform tsunami flow and that sand settles out of suspension forming a deposit when the flow velocity decreases to zero. Using flow depths constrained by numerical tsunami simulations for Cannon Beach, the sediment transport model calculated flow speeds of 6.5?C7.6?m/s for sites within 0.6?km of the beach and higher flow speeds (~8.8?m/s) for sites 0.8?C1.2?km inland. Flow speed calculated for sites within 0.6?km of the beach compare well with maximum velocities estimated for the largest tsunami simulation. The higher flow speeds calculated for the two sites furthest landward contrast with much lower maximum velocities (<3.8?m/s) predicted by numerical simulations. Grain size distributions of sand layers from the most distal sites are inconsistent with deposition from sediment falling out of suspension. We infer that rapid deceleration in tsunami flow and convergences in sediment transport formed unusually thick deposits. Consequently, higher flow speeds calculated by the sediment model probably overestimate the actual wave speed at sites furthest inland.  相似文献   

17.
On October 25, 2010, a large earthquake occurred off the coast of the Mentawai islands in Indonesia, generating a tsunami that caused damage to the coastal area of North Pagai, South Pagai, and Sipora islands. Field surveys were conducted soon after the event by several international survey teams, including the authors’. These surveys clarified the tsunami height distribution, the damage that took place, and residents’ awareness of tsunamis in the affected islands. Heights of over 5 m were recorded on the coastal area of the Indian Ocean side of North and South Pagai islands and the south part of Sipora island. In some villages, it was difficult to evacuate immediately after the earthquake because of the lack of routes to higher ground or the presence of rivers. Residents in some villages had taken part in tsunami drills or education; however, not all villages shared awareness of tsunami threats. In the present paper, based on the results of these field surveys, the vulnerability of these islands with regards to future tsunami threats was analyzed. Three important aspects of this tsunami disaster, namely the geographic disadvantage of the islands, the resilience of buildings and other infrastructure, and people’s awareness of tsunamis, are discussed in detail, and corresponding tsunami mitigation strategies are explained.  相似文献   

18.
December 2004 tsunami in the Indian Ocean region has been simulated using MIKE-21 HD model. The vertical displacement of the seabed is incorporated into the numerical simulation by using time-varying bathymetry data. In the open ocean, sea surface height from altimeter observation has been used to validate the model results. To the west of the rupture zone, the crest is observed to precede the trough of the tsunami waves while to the east, trough preceded the crest. The model performance along the coastal region has been validated using de-tided sea levels from tide gauge measurements at Tuticorin, Chennai, Vishakapattanam, and Paradip ports along the east coast of India. Unique coastal characteristics of the tsunami waves, wave height, and wave celerity are reasonably simulated by the numerical model. Spectral analysis of tide gauge observations and corresponding model results has been done, and the distribution of frequency peaks from the analysis of gauge observations and the model results is observed to have a reasonable comparison. Low-frequency waves, contributed from the coastally trapped edge waves, are found to dominate both the tide gauge observations and the model results. The subsequent increase in the tsunami wave height observed at Chennai, Vishakapattanam, and Paradip has been explained on the basis of coastally trapped edge waves. From the validation studies using altimeter data and tide gauge data, it is observed that the model can be used effectively to simulate the tsunami wave height in the offshore as well as in the coastal region with satisfying performance.  相似文献   

19.
A large amount of buildings was damaged or destroyed by the 2011 Great East Japan tsunami. Numerous field surveys were conducted in order to collect the tsunami inundation extents and building damage data in the affected areas. Therefore, this event provides us with one of the most complete data set among tsunami events in history. In this study, fragility functions are derived using data provided by the Ministry of Land, Infrastructure and Transportation of Japan, with more than 250,000 structures surveyed. The set of data has details on damage level, structural material, number of stories per building and location (town). This information is crucial to the understanding of the causes of building damage, as differences in structural characteristics and building location can be taken into account in the damage probability analysis. Using least squares regression, different sets of fragility curves are derived to demonstrate the influence of structural material, number of stories and coastal topography on building damage levels. The results show a better resistant performance of reinforced concrete and steel buildings over wood or masonry buildings. Also, buildings taller than two stories were confirmed to be much stronger than the buildings of one or two stories. The damage characteristic due to the coastal topography based on limited number of data in town locations is also shortly discussed here. At the same tsunami inundation depth, buildings along the Sanriku ria coast were much greater damaged than buildings from the plain coast in Sendai. The difference in damage states can be explained by the faster flow velocities in the ria coast at the same inundation depth. These findings are key to support better future building damage assessments, land use management and disaster planning.  相似文献   

20.
The paper is a report of the field campaign undertaken by an international team (Italian, French and Indonesian) a few weeks after the occurrence of a tsunami invading the south-eastern coast of Java (Indonesia) and it complements the results of a concurrent field survey by Asian and USA researchers. The tsunamigenic earthquake occurred on 3 of June 1994 in the Indian Ocean about 200 km south of Java. The tsunami caused severe damage and claimed many victims in some coastal villages. The main purpose of the survey was to measure the inundation and the runup values as well as to ascertain the possible morphological changes caused by the wave attacks. Attention was particularly focussed on the most affected districts, that is Lumajang, Jember and Banyuwangi in Java, although also the districts of Negera, Tebanan and Denpasar in Bali were examined. The most severe damage was observed in the Banyuwangi district, where the villages of Rajekwesi, Pancer and Lampon were almost completely levelled by the violent waves. Most places were hit by three significant waves with documented wave height often exceeding 5 m. The maximum runup value (9.50 m) was measured at Rajekwesi, where also the most impressive erosion phenomena could be found. In contrast, only in one place of the neighbouring island of Bali was there a slight tsunami, the rest of the island being practically unaffected.  相似文献   

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