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1.
We modeled a tsunami from the West Papua, Indonesia earthquakes on January 3, 2009 (M w?=?7.7). After the first earthquake, tsunami alerts were issued in Indonesia and Japan. The tsunami was recorded at many stations located in and around the Pacific Ocean. In particular, at Kushimoto on Kii Peninsula, the maximum amplitude was 43?cm, larger than that at Manokwari on New Guinea Island, near the epicenter. The tsunami was recorded on near-shore wave gauges, offshore GPS sensors and deep-sea bottom pressure sensors. We have collected more than 150 records and used 72 stations?? data with clear tsunami signals for the tsunami source modeling. We assumed two fault models (single fault and five subfaults) which are located to cover the aftershock area. The estimated average slip on the single fault model (80?×?40?km) is 0.64?m, which yields a seismic moment of 1.02?×?1020?Nm (M w?=?7.3). The observed tsunami waveforms at most stations are well explained by this model.  相似文献   

2.
The effect of distributed coseismic slip on progressive, near-field edge waves is examined for continental shelf tsunamis. Detailed observations of edge waves are difficult to separate from the other tsunami phases that are observed on tide gauge records. In this study, analytic methods are used to compute tsunami edge waves distributed over a finite number of modes and for uniformly sloping bathymetry. Coseismic displacements from static elastic theory are introduced as initial conditions in calculating the evolution of progressive edge-waves. Both simple crack representations (constant stress drop) and stochastic slip models (heterogeneous stress drop) are tested on a fault with geometry similar to that of the M w = 8.8 2010 Chile earthquake. Crack-like ruptures that are beneath or that span the shoreline result in similar longshore patterns of maximum edge-wave amplitude. Ruptures located farther offshore result in reduced edge-wave excitation, consistent with previous studies. Introduction of stress-drop heterogeneity by way of stochastic slip models results in significantly more variability in longshore edge-wave patterns compared to crack-like ruptures for the same offshore source position. In some cases, regions of high slip that are spatially distinct will yield sub-events, in terms of tsunami generation. Constructive interference of both non-trapped and trapped waves can yield significantly larger tsunamis than those that produced by simple earthquake characterizations.  相似文献   

3.
On the evening of March 28, 2005 at 11:09?p.m. local time (16:09 UTC), a large earthquake occurred offshore of West Sumatra, Indonesia. With a moment magnitude (M w) of 8.6, the event caused substantial shaking damage and land level changes between Simeulue Island in the north and the Batu Islands in the south. The earthquake also generated a tsunami, which was observed throughout the source region as well as on distant tide gauges. While the tsunami was not as extreme as the tsunami of December 26th, 2004, it did cause significant flooding and damage at some locations. The spatial and temporal proximity of the two events led to a unique set of observational data from the earthquake and tsunami as well as insights relevant to tsunami hazard planning and education efforts.  相似文献   

4.
The 1963 great Kurile earthquake was an underthrust earthquake occurred in the Kurile?CKamchatka subduction zone. The slip distribution of the 1963 earthquake was estimated using 21 tsunami waveforms recorded at tide gauges along the Pacific and Okhotsk Sea coasts. The extended rupture area was divided into 24 subfaults, and the slip on each subfault was determined by the tsunami waveform inversion. The result shows that the largest slip amount of 2.8?m was found at the shallow part and intermediate depth of the rupture area. Large slip amounts were found at the shallow part of the rupture area. The total seismic moment was estimated to be 3.9?×?1021?Nm (Mw 8.3). The 2006 Kurile earthquake occurred right next to the location of the 1963 earthquake, and no seismic gap exists between the source areas of the 1963 and 2006 earthquakes.  相似文献   

5.
Heterogeneous fault motion of the 1993 Hokkaido Nansei-Oki earthquake is studied by using seismic, geodetic and tsunami data, and the tsunami generation from the fault model is examined. Seismological analyses indicate that the focal mechanism of the first 10 s, when about a third of the total moment was released, is different from the overall focal mechanism. A joint inversion of geodetic data on Okushiri Island and the tide gauge records in Japan and Korea indicates that the largest slip, about 6 m, occurred in a small area just south of the epicenter. This corresponds to the initial rupture on a fault plane dipping shallowly to the west. The slip on the northernmost subfault, which is dipping to the east, is about 2 m, while the slips on the southern subfaults, which are steeply dipping to the west, are more than 3 m. Tsunami heights around Okushiri Island are calculated from the heterogeneous fault model using different grid sizes. Computation on the smaller grids produces large tsunami height that are closer to the observed tsunami runup heights. Tsunami propagation in the nearly closed Japan Sea is examined as the free oscillation of the Japan Sea. The excitation of the free oscillation by this earthquake is smaller than that by the 1964 Niigata or 1983 Japan Sea earthquake.  相似文献   

6.
The effect of offshore coral reefs on the impact from a tsunami remains controversial. For example, field surveys after the 2004 Indian Ocean tsunami indicate that the energy of the tsunami was reduced by natural coral reef barriers in Sri Lanka, but there was no indication that coral reefs off Banda Aceh, Indonesia had any effect on the tsunami. In this paper, we investigate whether the Great Barrier Reef (GBR) offshore Queensland, Australia, may have weakened the tsunami impact from the 2007 Solomon Islands earthquake. The fault slip distribution of the 2007 Solomon Islands earthquake was firstly obtained by teleseismic inversion. The tsunami was then propagated to shallow water just offshore the coast by solving the linear shallow water equations using a staggered grid finite-difference method. We used a relatively high resolution (approximately 250 m) bathymetric grid for the region just off the coast containing the reef. The tsunami waveforms recorded at tide gauge stations along the Australian coast were then compared to the results from the tsunami simulation when using both the realistic 250 m resolution bathymetry and with two grids having fictitious bathymetry: One in which the the GBR has been replaced by a smooth interpolation from depths outside the GBR to the coast (the “No GBR” grid), and one in which the GBR has been replaced by a flat plane at a depth equal to the mean water depth of the GBR (the “Average GBR” grid). From the comparison between the synthetic waveforms both with and without the Great Barrier Reef, we found that the Great Barrier Reef significantly weakened the tsunami impact. According to our model, the coral reefs delayed the tsunami arrival time by 5–10 minutes, decreased the amplitude of the first tsunami pulse to half or less, and lengthened the period of the tsunami.  相似文献   

7.
Surface sediment samples were collected from 5 pristine coastal areas and 1 potentially contaminated coastal site on Tutuila, the main island of American Samoa, an isolated island group in the South Pacific Ocean. Samples were analysed for total element analysis (15 elements) and mineralogy. The results indicated no evidence of trace element contamination at any site, including Pago Pago Harbour. Inter-site variations could be explained assuming the sediments consisted predominantly of coralline sand and rubble with varying quantities of basaltic materials derived from local catchments.  相似文献   

8.
Field Survey of the 27 February 2010 Chile Tsunami   总被引：1，自引：0，他引：1  
On 27 February 2010, a magnitude M w?=?8.8 earthquake occurred off the coast of Chile??s Maule region causing substantial damage and loss of life. Ancestral tsunami knowledge from the 1960 event combined with education and evacuation exercises prompted most coastal residents to spontaneously evacuate after the earthquake. Many of the tsunami victims were tourists in coastal campgrounds. The international tsunami survey team (ITST) was deployed within days of the event and surveyed 800?km of coastline from Quintero to Mehuín and the Pacific Islands of Santa María, Mocha, Juan Fernández Archipelago, and Rapa Nui (Easter). The collected survey data include more than 400 tsunami flow depth, runup and coastal uplift measurements. The tsunami peaked with a localized runup of 29?m on a coastal bluff at Constitución. The observed runup distributions exhibit significant variations on local and regional scales. Observations from the 2010 and 1960 Chile tsunamis are compared.  相似文献   

9.
The major (M w = 8.8) Chilean earthquake of 27 February 2010 generated a trans-oceanic tsunami that was observed throughout the Pacific Ocean. Waves associated with this event had features similar to those of the 1960 tsunami generated in the same region by the Great (M w = 9.5) 1960 Chilean Earthquake. Both tsunamis were clearly observed on the coast of British Columbia. The 1960 tsunami was measured by 17 analog pen-and-paper tide gauges, while the 2010 tsunami was measured by 11 modern digital coastal tide gauges, four NEPTUNE-Canada bottom pressure recorders located offshore from southern Vancouver Island, and two nearby open-ocean DART stations. The 2010 records were augmented by data from seven NOAA tide gauges on the coast of Washington State. This study examines the principal characteristics of the waves from the 2010 event (height, period, duration, and arrival and travel times) and compares these properties for the west coast of Canada with corresponding properties of the 1960 tsunami. Results show that the 2010 waves were approximately 3.5 times smaller than the 1960 waves and reached the British Columbia coast 1 h earlier. The maximum 2010 wave heights were observed at Port Alberni (98.4 cm) and Winter Harbour (68.3 cm); the observed periods ranged from 12 min at Port Hardy to 110–120 min at Prince Rupert and Port Alberni and 150 min at Bamfield. The open-ocean records had maximum wave heights of 6–11 cm and typical periods of 7 and 15 min. Coastal and open-ocean tsunami records revealed persistent oscillations that “rang” for 3–4 days. Tsunami energy occupied a broad band of periods from 3 to 300 min. Estimation of the inverse celerity vectors from cross-correlation analysis of the deep-sea tsunami records shows that the tsunami waves underwent refraction as they approached the coast of Vancouver Island with the direction of the incoming waves changing from an initial direction of 340° True to a direction of 15° True for the second train of waves that arrived 7 h later after possible reflection from the Marquesas and Hawaiian islands.  相似文献   

10.
The Transoceanic 1755 Lisbon Tsunami in Martinique   总被引：1，自引：0，他引：1  
On 1 November 1755, a major earthquake of estimated M w=8.5/9.0 destroyed Lisbon (Portugal) and was felt in the whole of western Europe. It generated a huge transoceanic tsunami that ravaged the coasts of Morocco, Portugal and Spain. Local extreme run-up heights were reported in some places such as Cape St Vincent (Portugal). Great waves were reported in the Madeira Islands, the Azores and as far as the Antilles (Caribbean Islands). An accurate search for historical data allowed us to find new (unpublished) information concerning the tsunami arrival and its consequences in several islands of the Lesser Antilles Arc. In some places, especially Martinique and the Guadeloupe islands, 3?m wave heights, inundation of low lands, and destruction of buildings and boats were reported (in some specific locations probably more enclined to wave amplification). In this study, we present the results of tsunami modeling for the 1755 event on the French island of Martinique, located in the Lesser Antilles Arc. High resolution bathymetric grids were prepared, including topographic data for the first tens of meters from the coastline, in order to model inundations on several sites of Martinique Island. In order to reproduce as well as possible the wave coastal propagation and amplification, the final grid was prepared taking into account the main coastal features and harbour structures. Model results are checked against historical data in terms of wave arrival, polarity, amplitude and period and they correlate well for Martinique. This study is a contribution to the evaluation of the tele-tsunami impact in the Caribbean Islands due to a source located offshore of Iberia and shows that an 8.5 magnitude earthquake located in the northeastern Atlantic is able to generate a tsunami that could impact the Caribbean Islands. This fact must be taken into account in hazard and risk studies for this area.  相似文献   

11.
The 2010 Mentawai earthquake (magnitude 7.7) generated a destructive tsunami that caused more than 500 casualties in the Mentawai Islands, west of Sumatra, Indonesia. Seismological analyses indicate that this earthquake was an unusual “tsunami earthquake,” which produces much larger tsunamis than expected from the seismic magnitude. We carried out a field survey to measure tsunami heights and inundation distances, an inversion of tsunami waveforms to estimate the slip distribution on the fault, and inundation modeling to compare the measured and simulated tsunami heights. The measured tsunami heights at eight locations on the west coasts of North and South Pagai Island ranged from 2.5 to 9.3 m, but were mostly in the 4–7 m range. At three villages, the tsunami inundation extended more than 300 m. Interviews of local residents indicated that the earthquake ground shaking was less intense than during previous large earthquakes and did not cause any damage. Inversion of tsunami waveforms recorded at nine coastal tide gauges, a nearby GPS buoy, and a DART station indicated a large slip (maximum 6.1 m) on a shallower part of the fault near the trench axis, a distribution similar to other tsunami earthquakes. The total seismic moment estimated from tsunami waveform inversion was 1.0 × 1021 Nm, which corresponded to Mw 7.9. Computed coastal tsunami heights from this tsunami source model using linear equations are similar to the measured tsunami heights. The inundation heights computed by using detailed bathymetry and topography data and nonlinear equations including inundation were smaller than the measured ones. This may have been partly due to the limited resolution and accuracy of publically available bathymetry and topography data. One-dimensional run-up computations using our surveyed topography profiles showed that the computed heights were roughly similar to the measured ones.  相似文献   

12.
The slip distribution and seismic moment of the 2010 and 1960 Chilean earthquakes were estimated from tsunami and coastal geodetic data. These two earthquakes generated transoceanic tsunamis, and the waveforms were recorded around the Pacific Ocean. In addition, coseismic coastal uplift and subsidence were measured around the source areas. For the 27 February 2010 Maule earthquake, inversion of the tsunami waveforms recorded at nearby coastal tide gauge and Deep Ocean Assessment and Reporting of Tsunamis (DART) stations combined with coastal geodetic data suggest two asperities: a northern one beneath the coast of Constitucion and a southern one around the Arauco Peninsula. The total fault length is approximately 400 km with seismic moment of 1.7 × 1022 Nm (Mw 8.8). The offshore DART tsunami waveforms require fault slips beneath the coasts, but the exact locations are better estimated by coastal geodetic data. The 22 May 1960 earthquake produced very large, ~30 m, slip off Valdivia. Joint inversion of tsunami waveforms, at tide gauge stations in South America, with coastal geodetic and leveling data shows total fault length of ~800 km and seismic moment of 7.2 × 1022 Nm (Mw 9.2). The seismic moment estimated from tsunami or joint inversion is similar to previous estimates from geodetic data, but much smaller than the results from seismic data analysis.  相似文献   

13.
基于日本南海海槽地震活动性和历史海啸事件记载的分析,本文对日本南海海槽发生MW9.1罕遇地震情况下的海啸进行了数值模拟研究.结果表明:该地震可引发初始波幅约10 m的海啸,6个小时后传至浙江沿海,近岸各处波幅为1—2 m;8个小时后靠近上海海岸线,最大波幅约2 m,受地形影响局地爬高至近3 m;11个小时后抵达苏北黄海沿岸,预计波幅普遍在1 m左右.海啸的上岸高度与海岸附近的海深和海岸线的形态密切相关.我国近岸海域地形变化复杂,海湾众多,对海啸波有放大作用,该模拟结果可能比实际传播到近岸时偏小,因此综合评估日本海啸影响我国华东地区的规模m可达1—2级左右.一旦日本南海发生罕遇地震对我国的影响不容忽视,尤其遇上风暴潮与天文大潮叠加,则可能会造成一定程度的海啸灾害.   相似文献   

14.
固体潮观测中的震颤异常波   总被引：8，自引：1，他引：7       下载免费PDF全文
在地震与固体潮台站的日常监测中,常发现有一些异常"脉动"信号叠加在固体潮曲线上.这些异常"脉动"与宽频带数字地震计的观测在时间上同步、一致,其中的一部分由发生在西太平洋上的热带气旋引起,而其他的则大多与强地震相伴随,统称为震颤异常波.本文介绍了华中科技大学的地震与固体潮观测台站(HUST)的概况,报道了该台应用 DZW重力仪和VS-1倾斜仪观测记录到的大量震颤异常波事例.大量观测事实表明:中国固体潮台站记录的震颤异常波,绝大多数只在DZW重力仪和VS-1倾斜仪的低通滤波1 通道(LP1)出现,而在其低通滤波2通道(LP2)和其他固体潮仪器中则罕有发现;震颤异常波的包络线大多呈"纺锤状"或"尾巴状",持续时间多为1~3天. 通过对震颤异常波和固体潮观测仪器的分析研究,得到以下结论:震颤异常波实际上就是一种来源复杂的地球脉动信号,响应范围广泛,可被宽频带数字地震计和固体潮仪器记录.由西太平洋上的热带气旋引起的震颤异常波的主要周期在3~7 s范围,而强震前的震颤异常波则除此外,还包含10~60 s及更长周期的信号.固体潮仪器对震颤异常波响应的差异是因为仪器的传递函数不同和特性所致. DZW重力仪和VS-1倾斜仪分钟值采样数据中的震颤异常波,只是真实信号的一种"混叠"或映射.强震前的震颤异常波是否与地震有关？是否是震兆？尚需做更深入细致的分析和研究.  相似文献   

15.
We studied the 11 March 2011 Tohoku tsunami through analysis of the sea level records from 21 tide gauge and 16 DART (Deep-ocean Assessment and Reporting of Tsunamis) stations from across the Pacific Ocean. The extreme power of this trans-oceanic tsunami was indicated by the trough-to-crest heights of 3.03 m at Arena Cove on the western coast of the USA and 3.94 m at Coquimbo on the southern coast of Chile. The average value of the maximum amplitude was 163.9 cm for the examined tide gauge records. At many coastal tide gauge stations the largest wave arrived several hours after the first arrival of the tsunami wave, and the tsunami lasted for a long time with an average duration of 4 days. On the contrary, at most of the DART stations in the deep ocean, the first wave was the largest, the tsunami amplitudes were smaller with an average maximum of 51.2 cm, and the durations were shorter with an average of 2 days. The two dominant tsunami periods on the DART records were 37 and 67.4 min, which are possibly attributed to the width and length of the tsunami source fault, respectively. The dimensions of the tsunami source was estimated as 233 km × 424 km. Wavelet analyses of tide gauge and DART records showed that most of the tsunami energy was distributed at the wide period band of around 10–80 min during the first hour after the tsunami arrival, then it was concentrated in a relatively narrower band. The frequency-time plots showed the switches and lapses of tsunami energy at the 35- and 65-min period bands.  相似文献   

16.
运用地震破裂过程快速反演方法,在2009年9月29日萨摩亚群岛地区地震发生后,采用全球地震台网(GSN)的宽频带地震资料,快速反演了这次地震的破裂过程,并于震后3.5小时内得出了这次地震破裂过程的反演结果.结果表明,这次萨摩亚群岛地区地震的破裂过程具有如下基本特征:①矩震级约为MW8.0;②地震主要破裂持续时间约为138s;③滑动量在断层面上的分布比较复杂,整个地震破裂包含至少2个滑动量较大的区域;④这次地震基本上是一次单侧破裂事件,破裂主要朝向西北方向.  相似文献   

17.
The tsunami generated by the 1 November, 1755 earthquake off the coast of Portugal affected mainly the coastlines of the Iberian Peninsula and Northwest Morocco, but was also observed in some places along the North Atlantic coasts. To determine whether the event could have effected the French coastline, we conducted a study to search for signs of the tsunami in historical records from all tide gauge stations off the French Atlantic coast during the twentieth century, specifically for the 28 February, 1969 and the 26 May, 1975 tsunamis that were recorded by the Portuguese tide gauge network. Because many recordings are available in La Rochelle (located on the southwest coast of France), we focused our study on this harbor. The analysis of the tide gauge data shows no evidence for tsunamis in La Rochelle, neither in 1969 nor in 1975. To confirm this lack of tsunami signals, we used nonlinear, shallow water equations to compute the tsunami propagation to the French Atlantic coastline for both 1969 and 1975 events. Results obtained from these simulations confirm otherwise unnoticeable wave amplitudes at La Rochelle harbor. In a second step, tsunamis from three different scenarios for the 1755 earthquake were modeled to estimate the impact of such a tsunami on the French Atlantic coast, with a focus on La Rochelle harbor. A comparison of the functions of tide configuration was made in order to analyse the difference in impact. The results show that, while the harbor is poorly impacted, several areas (western part of the island of Ré and northern coast of the island of Oléron) may have experienced a moderate impact from 0.5 to 1 m, especially since the tide was high at the time of arrival, possibly causing local inundations in lowland areas.  相似文献   

18.
The tsunami event generated by the great Sumatra–Andaman earthquake on 26 December 2004 was simulated with the recently developed model TsunAWI. The model is based on the finite element method, which allows for a very flexible discretization of the model domain. This is demonstrated by a triangulation of the whole Indian Ocean with a resolution of about 14 km in the deep ocean but a considerably higher resolution of about 500 m in the coastal area. A special focus is put on the Banda Aceh region in the Northern tip of Sumatra. This area was heavily hit by the tsunami and the highest resolution in this area is about 40 m in order to include inundation processes in the model simulation. We compare model results to tide gauge data from all around the Indian Ocean, to satellite altimetry, and field measurements of flow depth in selected locations of the Aceh region. Furthermore, we compare the model results of TsunAWI to the results of a nested grid model (TUNAMI-N3) with the same initial conditions and identical bathymetry and topography in the Aceh region. It turns out that TsunAWI gives accurate estimates of arrival times in distant locations and in the same mesh gives good inundation results when compared to field measurements and nested grid results.  相似文献   

19.
This paper presents a comparison of two tsunami forecasting systems: the NOAA/PMEL system (SIFT) and the Australian Bureau of Meteorology system (T1). Both of these systems are based on a tsunami scenario database and both use the same numerical model. However, there are some major differences in the way in which the scenarios are constructed and in the implementation of the systems. Two tsunami events are considered here: Tonga 2006 and Sumatra 2007. The results show that there are some differences in the distribution of maximum wave amplitude, particularly for the Tonga event, however both systems compare well to the available tsunameter observations. To assess differences in the forecasts for coastal amplitude predictions, the offshore forecast results from both systems were used as boundary conditions for a high-resolution model for Hilo, Hawaii. The minor differences seen between the two systems in deep water become considerably smaller at the tide gauge and both systems compare very well with the observations.  相似文献   

20.
本文假设马尼拉海沟北段为潜在海啸源,基于中国地震台网对马尼拉海沟地区震级测定偏差,采用COMCOT(comell Multi-grid Coupled Tsunami Model)海啸数值模型,模拟南海海啸波传播.选取南海北缘3个特定地点,其中两个位于华南近海区域,另一个位于台湾岛南端近海区域,此外还在临近马尼拉海沟北段的深海地区选取了1个特定地点.分析这些特定地点最大海啸波以及最大海啸波到时对于震级测定偏差的敏感性.结果表明:马尼拉海沟北段地震如触发海啸,华南近海区域以及台湾岛南部近海区域最大海啸波振幅对震级偏差敏感,但最大海啸波振幅到时对于震级测定偏差不敏感;振幅最大的海啸波,二十几分钟即可波及台湾岛南端近岸区域,大约1小时后波及大陆华南近海北部区域.  相似文献   

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