Tsunami Intensity Mapping Along the Coast of Tamilnadu (India) During the Deadliest Indian Ocean Tsunami of December 26, 2004

This paper presents tsunami intensity mapping and damage patterns along the surveyed coast of Tamilnadu (India) of the deadly Indian Ocean tsunami of December 26, 2004. The tsunami caused severe damage and claimed many victims in the coastal areas of eleven countries bordering the Indian Ocean. A twelve-stage tsunami intensity scale proposed by Papadopoulos and Imamura (2001) was followed to assign the intensity at the visited localities. Along the coast of the Indian mainland, tsunami damage sustained exclusively. Most severe damage was observed in Nagapattinam Beach, Nabiyarnagar, Vellaipalyam, and the Nagapattinam Port of Nagapattinum District on the east coast and Keelamanakudy village of Kanyakumari District on the western coast of Tamilnadu. The maximum assigned tsunami intensity was X+ at these localities. Minimum intensity V⁺ was received along the coast of Thanjavur, Puddukkotai and Ramnathpuram Districts in Palk Strait. The general observation reported by many people was that the first arrival was a tsunami crest. The largest tsunami waves were first arrivals on the eastern coast and the second arrivals on the western coast. Along the coast, people were unaware of the tsunami, and no anomalous behavior of ocean animals was reported. Good correlation was observed between the severity of damage and the presence of shadow zone of Sri Lanka, reflected waves from Sri Lanka and the Maldives Islands, variation in the width of the continental shelf, elevation of the coast and the presence of breakwaters. The presence of medu (naturally elevated landmass very close to the sea shore and elongated parallel to the coast) reduced the impact of the tsunami on the built environment.     

Field Survey of Tsunami Effects in Sri Lanka due to the Sumatra-Andaman Earthquake of December 26, 2004

The December 26, 2004 Sumatra-Andaman earthquake that registered a moment magnitude (M_w) of 9.1 was one of the largest earthquakes in the world since 1900. The devastating tsunami that resulted from this earthquake caused more casualties than any previously reported tsunami. The number of fatalities and missing persons in the most seriously affected countries were Indonesia - 167,736, Sri Lanka - 35,322, India - 18,045 and Thailand - 8,212. This paper describes two field visits to assess tsunami effects in Sri Lanka by a combined team of Japanese and Sri Lankan researchers. The first field visit from December 30, 2004 – January 04, 2005 covered the western and southern coasts of Sri Lanka including the cities of Moratuwa, Beruwala, Bentota, Pereliya, Hikkaduwa, Galle, Talpe, Matara, Tangalla and Hambantota. The objectives of the first field visit were to investigate the damage caused by the tsunami and to obtain eyewitness information about wave arrival times. The second field visit from March 10–18, 2005 covered the eastern and southern coasts of Sri Lanka and included Trincomalee, Batticaloa, Arugam Bay, Yala National Park and Kirinda. The objectives of the second visit were mainly to obtain eyewitness information about wave arrival times and inundation data, and to take relevant measurements using GPS instruments.     

The 26 December 2004 Sumatra Tsunami: Analysis of Tide Gauge Data from the World Ocean Part 1. Indian Ocean and South Africa

The M_w = 9.3 megathrust earthquake of December 26, 2004 off the northwest coast of Sumatra in the Indian Ocean generated a catastrophic tsunami that was recorded by a large number of tide gauges throughout the World Ocean. Part 1 of our study of this event examines tide gauge measurements from the Indian Ocean region, at sites located from a few hundred to several thousand kilometers from the source area. Statistical characteristics of the tsunami waves, including wave height, duration, and arrival time, are determined, along with spectral properties of the tsunami records.     

Field Measurements and Numerical Simulations of the 2004 Tsunami Impact on the East Coast of Sri Lanka

This paper employs a numerical model of tsunami propagation together with documented observations and field measurements of the evidence left behind by the tsunami in December 2004, to identify and interpret the factors that have contributed to the significant spatial variability of the level of tsunami impact along the coastal belt of the eastern province of Sri Lanka. The model results considered in the present analysis include the distribution of the amplitude of the tsunami and the pattern of wave propagation over the continental shelf off the east coast, while the field data examined comprise the maximum water levels measured at or near the shoreline, the horizontal inundation distances and the number of housing and other buildings damaged. The computed maximum amplitude of the tsunami at water points nearest the shoreline along the east coast shows considerable variation ranging from 2.2 m to 11.4 m with a mean value of 5.7 m; moreover, the computed amplitudes agree well with the available field measurements. We also show that the shelf bathymetry off the east coast, particularly the submarine canyons at several locations, significantly influences the near-shore transformation of tsunami waves, and consequently, the spatial variation of the maximum water levels along the coastline. The measured values of inundation also show significant variation along the east coast and range from 70 m to 4560 m with a median value of 700 m. Our analyses of field data also show the dominant influence of the coastal topography and geomorphology on the extent of tsunami inundation. Furthermore, the measured inundation distances indicate no apparent correlation with the computed tsunami heights at the respective locations. We also show that both the computed tsunami heights and the measured inundation distances for the east coast closely follow the log-normal statistical distribution.     

Numerical Modelling of the 26th December 2004 Indian Ocean Tsunami for the Southeastern Coast of India

A numerical simulation of the 26th December, 2004 Indian Ocean tsunami of the Tamil Nadu coastal zone is presented. The simulation approach is based on a fully nonlinear Boussinesq tsunami propagation model and included an accurate computational domain and a robust coseismic source. The simulation is first confronted to available tide gauge and runup observations. The agreement between observations and the predicted wave heights allowed a reasonable validation of the simulation. As a result, a full picture of the tsunami impact is provided over the entire coastal zone Tamil Nadu. The processes responsible for coastal vulnerability are discussed.     

印尼8.7级地震海啸灾害及应急救援

本文介绍了2004年12月26日发生在印度尼西亚苏门答腊岛近海的8．7级地震后引发的大规模海啸对东南亚国家造成的灾难的情况、各受灾国的应急响应、国际救援及中国国际救援队前往印尼班达亚齐开展救援行动的情况。     

2004年12月26日印尼8.7级地震综述

本文给出了2004年12月26日印尼8．7级大地震的基本参数、区域构造背景、地震及海啸的损失情况及各国的应急反应,并提出了一些有益的建议。     

Source Fault Model of the 1771 Yaeyama Tsunami, Southern Ryukyu Islands, Japan, Inferred from Numerical Simulation

The 1771 Yaeyama tsunami is successfully reproduced using a simple faulting model without submarine landslide. The Yaeyama tsunami (M 7.4), which struck the southern Ryukyu Islands of Japan, produced unusually high tsunami amplitudes on the southeastern coast of Ishigaki Island and caused significant damage, including 12,000 casualties. Previous tsunami source models for this event have included both seismological faults and submarine landslides. However, no evidence of landslides in the source has been obtained, despite marine surveying of the area. The seismological fault model proposed in this study, describing a fault to the east of Ishigaki Island, successfully reproduces the distribution of tsunami runup on the southern coast of the Ryukyu Islands. The unusual runup heights are found through the numerical simulation attributable to a concentration of tsunami energy toward the southeastern coast of Ishigaki Island by the effect of the shelf to the east. Thus, the unusual runup heights observed on the southeastern coast of Ishigaki Island can be adequately explained by a seismological fault model with wave-ray bending on the adjacent shelf.     

The Event of 26th of December 2004 – The Biggest Earthquake in the World in the Last 40 years

A great earthquake occurred at 00:58:49 (UTC) on Sunday, December 26, 2004 off the northwest coast of Sumatra, Indonesia. Its revised moment magnitude was M 9.3 making it in the top four largest earthquakes in the world since 1900 and the largest since the Alaskan 1964 event. The earthquake caused tsunami waves which killed more than 300,000 people in Southern Asia and Africa. There were 31 earthquakes with magnitudes between 5.5 and 7.3 in the 48-h period after the main event, and it seemed that seismicity migrated northwards along the 1200 km fault (http: //www.ga.gov.au). Similar size events occurred in that location off Sumatra in the 19th century, but no evidence of written records of their tsunami effects in Australia is found. The devastating megathrust earthquake of 26 December 2004 occurred on the interface of the Indo-Australian and Euro-Asian plates where the first plate subducts beneath the overriding second plate and the Indo-Australian plate begins its descent into the mantle. In the epicentral region, the Indo-Australian plate moves toward the northeast at a rate of about 7 cm/year relative to the Euro-Asian plate resulting in oblique convergence and partitioning into thrust-faulting. From the size of the earthquake, it is likely that the displacement on the fault plane was up to fifteen meters. As with the recent event, megathrust earthquakes often generate large tsunamis that cause damage over a much wider area than is directly affected by ground shaking near the earthquake’s rupture. The subduction zone continues further south of the Indonesian archipelago and that area is also a potential risk of producing a megathrust event that may affect coastal parts of northwest Australia. The tragic events of Boxing Day 2004 highlighted the importance of establishing a tsunami warning system for the Indian Ocean like the one for the Pacific. Issues like more and better instrumentation, and a long-term program to educate people in the region about the dangers of tsunamis, were identified as priorities. Of particular interest is the time for identifying and issuing alerts for such devastating earthquakes with possibility to reduce it in future for warning purposes.     

印尼苏门答腊西8.7级地震的几个特点及由其引发的一些思考

分析总结了印尼苏门答腊西8．7级地震的几个特点：(1)板缘特大地震;(2)引发海啸,受灾范围特别大,成灾的瞬间突发性却不如内陆地震明显;(3)在远处出现“湖面波动”等同震现象突出;(4)震前全球地震活动出现异常图像;(5)安达曼弧一带与川滇地区强震活动存在相关性。并由此提出了：尽快加紧地震海啸预警机制研究及其技术系统的建立;加强地震预测预警机制研究;要重点研究川滇地区的地震危险性;强化防震减灾科普宣传等建议。     

Reconstruction of Tsunami Inland Propagation on December 26, 2004 in Banda Aceh, Indonesia, through Field Investigations

This paper presents the results from an extensive field data collection effort following the December 26, 2004 earthquake and tsunami in Banda Aceh, Sumatra. The data were collected under the auspices of TSUNARISQUE, a joint French-Indonesian program dedicated to tsunami research and hazard mitigation, which has been active since before the 2004 event. In total, data from three months of field investigations are presented, which detail important aspects of the tsunami inundation dynamics in Banda Aceh. These include measurements of runup, tsunami wave heights, flow depths, flow directions, event chronology and building damage patterns. The result is a series of detailed inundation maps of the northern and western coasts of Sumatra including Banda Aceh and Lhok Nga. Among the more important findings, we obtained consistent accounts that approximately ten separate waves affected the region after the earthquake; this indicates a high-frequency component of the tsunami wave energy in the extreme near-field. The largest tsunami wave heights were on the order of 35 m with a maximum runup height of 51 m. This value is the highest runup value measured in human history for a seismically generated tsunami. In addition, our field investigations show a significant discontinuity in the tsunami wave heights and flow depths along a line approximately 3 km inland, which the authors interpret to be the location of the collapse of the main tsunami bore caused by sudden energy dissipation. The propagating bore looked like a breaking wave from the landward side although it has distinct characteristics. Patterns of building damage are related to the location of the propagating bore with overall less damage to buildings beyond the line where the bore collapsed. This data set was built to be of use to the tsunami community for the purposes of calibrating and improving existing tsunami inundation models, especially in the analysis of extreme near-field events.     

The rotational and gravitational signature of the December 26, 2004 Sumatran earthquake

Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth’s mass thereby causing the Earth’s rotation and gravitational field to change. The size of this change depends upon the magnitude, focal mechanism, and location of the earthquake. The Sumatran earthquake of December 26, 2004 is the largest earthquake to have occurred since the 1960 Chilean earthquake. Using a spherical, layered Earth model, the coseismic effect of the Sumatran earthquake upon the Earth’s length-of-day, polar motion, and low-degree harmonic coefficients of the gravitational field are computed. Using a model of the earthquake source that is composed of five subevents having a total moment-magnitude M _w of 9.3, it is found that this earthquake should have caused the length-of-day to decrease by 6.8 microseconds, the position of the Earth’s generalized figure axis to shift 2.32 milliarcseconds towards 127° E longitude, the Earth’s oblateness J ₂ to decrease by 2.37 × 10⁻¹¹ and the Earth’s pear-shapedness J ₃ to decrease by 0.63 × 10⁻¹¹. The predicted change in the length-of-day, position of the generalized figure axis, and J ₃ are probably not detectable by current measurement systems. But the predicted change in oblateness is perhaps detectable if other effects, such as those of the atmosphere, oceans, and continental water storage, can be adequately removed from the observations.     

海啸波近岸共振响应的数值模拟及分析

应用有限差分方法求解非线性浅水长波方程,建立了海啸波产生和传播的二维数值模型;对太平洋地震引起的夏威夷群岛海啸波进行模拟,并将模拟结果和测站实测值进行比较,验证了模型的正确性。利用快速傅里叶变换对数值模拟结果进行谱分析,得到整个计算区域的能量谱分布,并给出了发生能量聚集的位置及相应的谱峰周期。讨论了海啸波传播到近岸时可能产生的共振响应现象,发现海啸波和近岸的共振响应不仅与近岸复杂地形有关,还与海啸波传播到近岸时的波浪入射方向有关。     

2004年12月26日印尼地震海啸与全球低温

气候潮汐循环说和海震调温说,阐明了冷气候、强潮汐和强震相互对应的物理机制,对2000年地球进入拉马德雷冷位相后的气候预测有重大科学意义.中国连续18年暖冬的终结是2000年地球进入拉马德雷冷位相和印尼发生地震海啸的合理结果.规律表明,在拉马德雷冷位相时期,全球强震、低温、飓风伴随拉尼娜、全球性流感伴随厄尔尼诺将越来越强烈.在20世纪50~70年代,强沙尘暴年与流感爆发年一一对应,沙尘暴可能传播禽流感。     

Modeling the seismic source and tsunami generation of the December 12, 1992 Flores Island,Indonesia, earthquake

On December 12, 1992 a large earthquake (M _s 7.5) occurred just north of Flores Island, Indonesia which, along with the tsunami it generated, killed more than 2,000 people. In this study, teleseismicP andSH waves, as well asPP waves from distances up to 123°, are inverted for the orientations and time histories of multiple point sources. By repeating the inversion for reasonable values of depth, time separation and spatial separation, a 2-fault model is developed. Next, the vertical deformation of the seafloor is estimated from this fault model. Using a detailed bathymetric model, linear and nonlinear tsunami propagation models are tested. The data consist of a single tide gauge record at Palopo (650 km to the north), as well as tsunami runup height measurements from Flores Island and nearby islands. Assuming a tsunami runup amplification factor of two, the two-fault model explains the tide gauge record and the tsunami runup heights on most of Flores Island. It cannot, however, explain the large tsunami runup heights observed near Leworahang (on Hading Bay) and Riangkroko (on the northeast peninsula). Massive coastal slumping was observed at both of these locations. A final model, which in addition to the two faults, includes point sources of large vertical displacement at these two locations explains the observations quite well.     

Features and formation processes of multiple deposition layers from the 2004 Indian Ocean Tsunami at Ban Nam Kem,southern Thailand

Multiple‐layered tsunami deposits have been frequently reported from coastal stratigraphic sequences, but the formation processes of these layers remain uncertain. A terrestrial sandy deposit formed by the 2004 Indian Ocean Tsunami was investigated at Ban Nam Kem, southern Thailand. Four internal layers induced by two tsunami waves were identified in the tsunami deposit. Sedimentary structures indicated that two units were formed by run‐up currents caused by the tsunami and the other two units were deposited by the backwash flows. Graded bedding was common in the layers, but inverse grading was observed at limited intervals on the surveyed transects. The characteristics of the multiple‐layered tsunami deposit vary remarkably over a very short distance (<1 m) in response to the local topography. Remarkable asymmetries in thickness and grain‐size distribution are recognized between the run‐up and backwash flow deposits. On the basis of the interpretation of sedimentary structures, the formation process of the multiple‐layered tsunami deposit observed in this study can be explained in a schematic model as the modification of the ideal tsunami sequence by local erosion and the asymmetric hydraulic properties of tsunami waves, such as the maximum shear velocity and the heterogeneity of the flow velocity field.     

Integral source characteristics of the Sumatra earthquakes of December 26, 2004, and March 28, 2005

The integral characteristics of source geometry, source duration, and rupture propagation for the Sumatra-Andaman earthquake of December 26, 2004 and for the March 28, 2005 earthquake near northern Sumatra have been determined. The source parameters were found by analyzing records of the higher orbits of long-period surface waves. The results are compared with the large-scale average characteristics of tomographic models for the source process based on different data sets that diverge in some details, as well as with the aftershock distribution for the considered earthquakes.     

Overview of Holocene Tsunami Deposits along the Nankai,Suruga, and Sagami Troughs,Southwest Japan

Tsunami deposits provide a basis for reconstructing Holocene histories of great earthquakes and tsunamis on the Pacific Coast of southwest Japan. The deposits have been found in the past 15 years at lakes, lagoons, outcrops, and archaeological excavations. The inferred tsunami histories span 3000 years for the Nankai and Suruga Troughs and nearly 10,000 years for the Sagami Trough. The inferred histories contain recurrence intervals of variable length. The shortest of these —100–200 years for the Nankai Trough, 150–300 years for the Sagami Trough — resemble those known from written history of the past 1000–1500 years. Longer intervals inferred from the tsunami deposits probably reflect variability in rupture mode, incompleteness of geologic records, and insufficient research. The region's tsunami history could be clarified by improving the geologic distinction between tsunami and storm, dating the inferred tsunamis more accurately and precisely, and using the deposits to help quantify the source areas and sizes of the parent earthquakes.     

The December 26, 2004, off the west coast of northern Sumatra, Indonesia, M_W=9.0, earthquake and the critical-point-like model of earthquake preparation

Introduction The unexpected December 26, 2004, off the west coast of northern Sumatra, Indonesia, MW=9.0 earthquake, which caused devastating tsunami around the Indian Ocean, reminds seis-mologists of the difficulty of earthquake forecast and/or prediction. For seismologists this earth-quake is almost completely unexpected, because there was neither forecasting (which means the estimation of the future earthquake rate as a function of location, time, and magnitude) nor predic-tion (forecasti…     

Numerical Modeling and Observations of Tsunami Waves in Alberni Inlet and Barkley Sound, British Columbia

Alberni Inlet is a long and narrow fjord adjacent to Barkley Sound on the Pacific Coast of Vancouver Island, Canada. Port Alberni, at the head of the inlet, was affected in 1964 by the largest Pacific tsunami waves in Canadian history. We use observations and results from two numerical models to investigate the resonant characteristics of the region and amplification of tsunami waves in Barkley Sound and Alberni Inlet. The first model (A) was forced at its open boundary with a stationary autoregressive signal, similar to the observed background noise. The second model (B) used an initial sea-level deformation from a potential earthquake off California in the southern segment of the Cascadia Subduction Zone, producing transient tsunami waves. Spectral, cross-spectral and frequency-time (f-t) analyses of the observations were used to examine the resonant properties and topographic response of the local area. The respective results show large admittance functions over a wide 0.5–0.9 cph frequency band, implying a low Q factor but high amplification of arriving waves. This unusual behavior is a result of two effects: A quarter-wave resonance of the system for its fundamental Helmholtz mode and amplification due to the narrowing of the channel cross section from Barkley Sound to Alberni Inlet. The model A numerical results agree favorably with the observations, indicating an energetic resonant mode at frequency of ~0.53 cph (112 min), with its nodal line located near the entrance to Barkley Sound and amplification factor value close to 12. The results from the tsunami propagation model (B) yield spectral characteristics similar to those from the model A and from the observations. The maximum tsunami current speed for this scenario is 2.4 ms^?1 in Sproat Narrows, which divides Alberni Inlet into two parts, while the largest computed wave height is 1.6 m in the northern Alberni Inlet, in the area of Port Alberni.