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1.
快速准确的海啸源模型是近场海啸精确预警的关键.尽管目前还没有办法直接对其进行正演定量计算,但是可以通过多源地震、海啸观测数据进行反演或联合反演推算.不同的海啸源可能导致不同的预警结论,了解不同类型海啸源适用性、评估海啸源特征差异对近场海啸的影响,无论对于海啸预警还是海啸模拟研究尤为重要.本文评估分析了6种不同同震断层模型对2011年3月11日日本东北地震海啸近场数值预报的影响,重点对比分析了有限断层模型与均一滑动场模型对近场海啸产生、传播、淹没特征的影响及各自的误差.研究表明:近场海啸波能量分布主要取决于海啸源分布特征,特别是走向角的差异对海啸能量分布影响较大;有限断层模型对海啸灾害最为严重的39°N以南沿岸地区的最大海啸爬坡高度明显优于均一滑动场模型结果;综合对比DART浮标、GPS浮标及近岸潮位站共32个站次的海啸波幅序列结果发现有限断层模型整体平均绝对/相对误差比均一滑动场模型平均误差要低,其中Fujii海啸源的平均绝对/相对误差最小,分别是0.56m和26.71%.UCSB海啸源的平均绝对/相对误差次之.3个均一滑动场模型中USGSCMT海啸源模拟精度最高.相对于深海、浅海观测站,有限断层模型比均一滑动场模型对近岸观测站计算精度更高.海啸源误差具有显著的方向性,可能与反演所采用的波形数据的代表性有关;谱分析结果表明Fujii海啸源对在12至60min主频波谱的模拟要优于UCSB海啸源.海啸源中很难真实反映海底地震破裂过程,然而通过联合反演海啸波形数据推算海啸源的方法可以快速确定海啸源,并且最大限度的降低地震破裂过程与海啸产生的不确定性带来的误差.  相似文献   

2.
海啸造成的灾害与损失并非都与淹没有关,特别是港口中海啸诱导的强流会对船只及海事设施产生重要的影响及损害.由于海啸流观测数据稀缺及海啸诱导涡流机制的不确定性,过去60年海啸科学主要集中于对海啸波特征及淹没过程的研究与分析,海啸流模拟及验证工作开展较少,导致对海啸流基本特征及其造成灾害现象的曲解.开展海啸诱导的涡流研究及预警服务显得尤为重要及紧迫.考虑快速海啸预警需要,综合对比海啸诱导涡流的物理框架及模型方法,探索兼顾效率与计算精度的海啸流模拟方法是本文的核心工作及出发点.通过分析浅层湍流相干结构(TCS)产生的主要物理耗散机制,确定了考虑2D水平耗散机制的非线性浅水方程可用于海啸涡流的模拟分析.基于高精、高分辨率有限体积模型Geoclaw建立了三个精细化的港口海啸流模型,模型分辨率为5m.利用基于海啸浮标反演的海啸源模型作为初始条件,模拟分析了日本东北地震海啸在远场的海啸波流特征.海啸波流特征模拟结果与观测吻合较好,结果可信.对比发现:波驱动的自由表面流,小的位相或波幅误差就会导致大的流速误差,流的模拟和预报相对波幅来说更具挑战性.研究了海啸波流能量在港池中的分布特征,得到:港池入口及防波堤两端常被强流控制,具有极高的危险性;相对于波幅的空间变化,海啸流具有更强的空间敏感性;所建立的高分辨率海啸模型模拟再现了日本海啸在近场的涡旋结构,给出了与观测基本一致的涡流特征.最后,引入海啸流危险等级标准,分析了港口海啸流危险性等级分布、船只疏散的安全深度及回港的时间周期.针对港口、海湾同时考虑海啸波流特征的海啸预警与评估对于港口应急管理者科学决策具有重要意义.  相似文献   

3.
一直以来,海啸波特征作为表征海啸潜在破坏性的参数指标得到了广泛应用,特别是针对近场极端海啸事件造成的灾害来说,这种表征具有较好的适用性.然而总结分析历史海啸事件造成的损失发现：在远场近岸及港湾系统中,海啸诱导的强流却是造成损失的主要原因.陆架或港湾振荡导致海啸波幅快速升降诱发强流,可能促使港工设施受到威胁及损害,进而对海啸预警服务及海事应急管理提出了新的挑战.因此,全面理解与评估海啸在港湾中诱发的灾害特征,探索港湾中海啸流的数值模拟方法,发展针对港湾尺度的海啸预警服务指导产品尤为迫切.受限于海啸流验证数据的缺乏及准确模拟海啸流技术方法的诸多不确定性,大部分海啸数值模拟研究工作主要是针对水位特征的研究及验证,可能导致对港湾中海啸灾害危险性认识的曲解与低估.本研究基于非线性浅水方程,针对夏威夷群岛三个典型港湾建立了精细化海啸数值模型（空间分辨率达到10 m）,并联合有限断层破裂模型计算分析了日本东北地震海啸在三个港湾及其邻近区域的海啸特征,波、流计算结果与实测结果吻合较好,精细化的海啸港湾模型模拟结果可信.模拟发现港湾中较小的波幅,同样可以产生强流.综合分析日本东北地震海啸波、流特征对输入条件不确定性的响应结果发现：港湾中海啸波-流能量的空间分布特征差异较大,这与港湾系统中海啸波的驻波特性相关;相比海啸波幅空间特征,海啸流特征具有更强的空间敏感性;海啸流时空分布特征对输入条件的不确定性响应比海啸波幅对这些不确定性的响应更强,海啸流的模拟与预报更有挑战性;不确定性对海啸流计算精度的影响会进一步传导放大港湾海啸流危险性的评估及对港工设施产生的应力作用的误差,合理的输入条件对海啸流的精确模拟至关重要.最后,希望通过本文的研究可以从海啸波-流特征角度更加全面认识近岸海啸灾害特征,拓展海啸预警服务的广度与深度,从而为灾害应急管理部门提供更加科学合理的辅助决策产品.  相似文献   

4.
Source model of Noto-Hanto-Oki earthquake tsunami of 7 February 1993   总被引：1，自引：0，他引：1  
A source model was discussed for a small tsunami accompanied by the Noto-Hanto-Oki earthquake (M s 6.6), striking Japan on 7 February, 1994. Assuming a fault model under the sea bottom, we estimated the focal parameters jointly, using synthesized tsunami source spectra as well as the tsunami numerical simulation. The fault proposed by this study consists of a plane sized 15×15 km, dipping N47°W with the dip angle of 42°, which is almost pure reverse fault (slip angle 87°) with a dislocation of 1 meter. The numerical simulation shows that the shallow sea in the source region caused a comparatively long recurring tsunami (the periods are 12–18 minutes) in spite of its small size. The model fault is corresponding to an aftershock area of this earthquake.  相似文献   

5.
Storm- and tsunami-deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods. Here we propose an original approach to identify tsunami-induced deposits by combining numerical simulation and rock magnetism. To test our method, we investigate the tsunami deposit of the Boca do Rio estuary generated by the 1755 earthquake in Lisbon which is well described in the literature. We first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave. Then we use concentration (MS, SIRM) and grain size (χARM, ARM, B1/2, ARM/SIRM) sensitive magnetic proxies coupled with SEM microscopy to unravel the magnetic mineralogy of the tsunami-induced deposit and its associated depositional mechanisms. In order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary, magnetic data were processed by multivariate statistical analyses. Our numerical simulation show a large inundation of the estuary with flow depths varying from 0.5 to 6 m and run up of ～7 m. Magnetic data show a dominance of paramagnetic minerals (quartz) mixed with lesser amount of ferromagnetic minerals, namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units. Multivariate statistical analyses indicate a better connection between the tsunami-induced deposit and a mixture of Units C and D. All these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth. The method tested here represents an original and promising tool to identify tsunami-induced deposits in similar embayed beach environments.  相似文献   

6.
—The 1994 great Kuril earthquake generated an unusual tsunami that was observed at five tide gauges on the Hokkaido coast of the Okhotsk Sea. The tsunami arrived at tide gauges considerably earlier than the expected time, calculated on the assumption that the tsunami source area coincides with the aftershock area. Numerical simulation of the tsunami shows that the first wave of the tsunami in the Okhotsk Sea was generated by the significant subsidence north of the Kuril Islands. It is assumed that this subsidence is due to the earthquake. The coseismic deformation area of the ocean bottom extended over a vastly larger area than the aftershock area or the rupture area for the Kuril earthquake. The numerical simulation also shows that the tsunami observed at Utoro during the first hour after the origin time of the earthquake was mainly generated by the horizontal movement of the sloping ocean bottom near the Shiretoko Peninsula.  相似文献   

7.
The fault parameters of the Guam earthquake of August 8, 1993 are estimated from seismological analyses, and the possibility of identifying the actual fault plane from tsunami waveforms is tested. The Centroid Moment Tensor solution of long-period surface waves shows one nodal plane shallowly dipping to the north and the other nodal plane steeply dipping to the south. The seismic moment is 3.5×1020 Nm and the corresponding moment magnitude is 7.7. The Moment Tensor Rate Function inversion ofP waves also yields a similar focal mechanism and seismic moment. The point source depth is estimated as 40–50 km.This earthquake generated tsunamis that propagated toward the Japanese coast along the Izu-Bonin-Mariana ridge system. The tsunamis are recorded on ocean bottom pressure gauges and tide gauges. Numerical computation of tsunamis shows that the computed waveforms from the two possible fault planes match well with the observed tsunami waveforms. The numerical computation also shows that the tsunami waveforms at Guam Island, just above the fault, should contain useful information regarding the identification of the actual fault plane. However, the current sampling rate of the tide gauges is so small that the records cannot help the identification.  相似文献   

8.
1604年泉州海外大地震及其海啸影响分析   总被引：1，自引：0，他引：1  
黄昭  王善雄  王喜年 《地震》2006,26(4):94-102
由于史料记载的模糊和局限性, 1604年泉州海外8级大地震是否引发地震海啸灾难, 一直是有争议的。 该文从这次地震历史资料的辨别、 考证和分析研究认为, 泉州海外大地震并未引发地震海啸产生的显著灾害。 在相关的史料与台湾海峡发震构造的分析基础上, 通过潜在海啸源的鉴别以及海啸源参数的确定, 对泉州滨海断裂和台湾海峡浅滩南缘海啸源进行数值模拟计算。 在计算过程中, 利用了1994年台湾海峡浅滩南缘地震的海啸波验潮站资料, 对计算模型和方法进行了检验。 1604年泉州海外大地震的潜在海啸源(滨海断裂)的数值计算结果表明, 海啸波对泉州湾沿岸的增减水效应不足以造成灾难性的影响, 因此也为1604年泉州海外大地震未引发灾难性的海啸提供了新的证据。  相似文献   

9.
The 27 December 1722 Algarve earthquake destroyed a large area in southern Portugal generating a local tsunami that inundated the shallow areas of Tavira. It is unclear whether its source was located onshore or offshore and, in any case, what was the tectonic source responsible for the event. We analyze available historical information concerning macroseismicity and the tsunami to discuss the most probable location of the source. We also review available seismotectonic knowledge of the offshore region close to the probable epicenter, selecting a set of four candidate sources. We simulate tsunamis produced by these candidate sources assuming that the sea bottom displacement is caused by a compressive dislocation over a rectangular fault, as given by the half-space homogeneous elastic approach, and we use numerical modeling to study wave propagation and run-up. We conclude that the 27 December 1722 Tavira earthquake and tsunami was probably generated offshore, close to 37°01′N, 7°49′W.  相似文献   

10.
We explored the distributional changes in tsunami height along the eastern coast of the Korean Peninsula resulting from virtual and historical tsunami earthquakes. The results confirm significant distributional changes in tsunami height depending on the location and magnitude of earthquakes. We further developed a statistical model to jointly analyse tsunami heights from multiple events, considering the functional relationships; we estimated parameters conveying earthquake characteristics in a Weibull distribution, all within a Bayesian regression framework. We found the proposed model effective and informative for the estimation of tsunami hazard analysis from an earthquake of a given magnitude at a particular location. Specifically, several applications presented in this study showed that the proposed Bayesian approach has the advantage of conveying the uncertainty of the parameter estimates and its substantial effect on estimating tsunami risk.  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 M w=9.3 megathrust earthquake of December 26, 2004 off the coast of Sumatra in the Indian Ocean generated a catastrophic tsunami that caused widespread damage in coastal areas and left more than 226,000 people dead or missing. The Sumatra tsunami was accurately recorded by a large number of tide gauges throughout the world's oceans. This paper examines the amplitudes, frequencies and wave train structure of tsunami waves recorded by tide gauges located more than 20,000 km from the source area along the Pacific and Atlantic coasts of North America.  相似文献   

13.
This study conducts coupled simulation of strong motion and tsunami using stochastically generated earthquake source models. It is focused upon the 2011 Tohoku, Japan earthquake. The ground motion time-histories are simulated using the multiple-event stochastic finite-fault method, which takes into account multiple local rupture processes in strong motion generation areas. For tsunami simulation, multiple realizations of wave profiles are generated by evaluating nonlinear shallow water equations with run-up. Key objectives of this research are: (i) to investigate the sensitivity of strong motion and tsunami hazard parameters to asperities and strong motion generation areas, and (ii) to quantify the spatial variability and dependency of strong motion and tsunami predictions due to common earthquake sources. The investigations provide valuable insights in understanding the temporal and spatial impact of cascading earthquake hazards. Importantly, the study also develops an integrated strong motion and tsunami simulator, which is capable of capturing earthquake source uncertainty. Such an advanced numerical tool is necessary for assessing the performance of buildings and infrastructure that are subjected to cascading earthquake–tsunami hazards.  相似文献   

14.
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   

15.
We studied two tsunamis from 2012, one generated by the El Salvador earthquake of 27 August (Mw 7.3) and the other generated by the Philippines earthquake of 31 August (Mw 7.6), using sea level data analysis and numerical modeling. For the El Salvador tsunami, the largest wave height was observed in Baltra, Galapagos Islands (71.1 cm) located about 1,400 km away from the source. The tsunami governing periods were around 9 and 19 min. Numerical modeling indicated that most of the tsunami energy was directed towards the Galapagos Islands, explaining the relatively large wave height there. For the Philippines tsunami, the maximum wave height of 30.5 cm was observed at Kushimoto in Japan located about 2,700 km away from the source. The tsunami governing periods were around 8, 12 and 29 min. Numerical modeling showed that a significant part of the far-field tsunami energy was directed towards the southern coast of Japan. Fourier and wavelet analyses as well as numerical modeling suggested that the dominant period of the first wave at stations normal to the fault strike is related to the fault width, while the period of the first wave at stations in the direction of fault strike is representative of the fault length.  相似文献   

16.
在东海潜在震源区冲绳海槽假定了五个震源点,根据Steven地震海啸地震参数经验值作为初始条件,分别考虑6.5、7.0、7.5、8.0、8.5、9.0级地震条件下的30个震例,采用数值模拟的方法,对海啸在东海传播过程进行情境分析,特别是对上海沿岸地区可能会遭受的海啸灾害做了较为精细的研究.结果发现:小于8.0级的震例对上海地区几乎不会造成影响;8.0级震例只有最北端震源点震例会对上海地区有明显影响;8.5级以及9.0级震级基本上均会对上海沿岸地区造成较大的影响.特别是冲绳海槽北段9.0级震例可能会对上海沿岸局部地区造成危害,最大波高可达3.9m.  相似文献   

17.
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   

18.
The giant Tohoku-Oki earthquake of 11 March 2011 in offshore Japan did not only generate tsunami waves in the ocean but also infrasound (or acoustic–gravity) waves in the atmosphere. We identified ultra-long-period signals (>500 s) in the recordings of infrasound stations in northeast Asia, the northwest Pacific, and Alaska. Their source was found close to the earthquake epicenter. Therefore, we conclude that in general, infrasound observations after a large offshore earthquake are evidence that the surface and the floor of the sea have been significantly vertically displaced by the earthquake and that a tsunami must be expected. Since infrasound is traveling faster than the tsunami, such information may be used for tsunami early warnings.  相似文献   

19.
徐起浩 《华南地震》2006,26(1):17-27
根据琼州府志、琼山县志及一些家谱、族谱等的记载,再加上对海域中退潮后海底残留的房屋、坟墓等各种沉没于海的人类活动废墟和东寨港海域中地震地貌的发现与考察,结合本人和前人以往的研究成果,证实1605年7月13日海南岛琼山县发生的71/2级强地震导致琼州海峡东南侧与琼北陆地相连的海底及与海相连的琼北东部一些沿岸陆地大面积同震快速下沉,使得原先为陆地的东寨港、北创港和舖前港及其以北海域等地区大面积陆陷成海。这是一次生源地在与海相连的海岸带的同震海岸下沉。推断了这次地震海啸;比较了这次陆陷成海地震海啸与生源地在近海和大洋海底的地震海啸的异同;也与北美西海岸生源地在太平洋板块斜插在北美大陆板块之下形成消减带的海岸同震下沉及海啸比较了异同。最后还提出,琼州大地震陆陷成海灾害应从根本上区别通常所说的震陷灾害。  相似文献   

20.
The tsunami caused by the 2007 Peru earthquake (Mw 8.0) provoked less damage than by the seismic shaking itself (numerous casualties due to the earthquake in the vicinity of Pisco). However, it propagated across the Pacific Ocean and small waves were observed on one tide gauge in Taiohae Bay (Nuku Hiva, Marquesas, French Polynesia). We invert seismological data to recover the rupture pattern in two steps. The first step uses surface waves to find a solution for the moment tensor, and the second step uses body waves to compute the slip distribution in the source area. We find the slip distribution to consist of two main slip patches in the source area. The inversion of surface waves yields a scalar moment of 8.9 1020 Nm, and body-wave inversion gives 1.4 1021 Nm. The inversion of tsunami data recorded on a single deep ocean sensor also can be used to compute a fault slip pattern (yielding a scalar moment of 1.1 1021 Nm). We then use these different sources to model the tsunami propagation across the Pacific Ocean, especially towards Nuku Hiva. While the source model taken from the body-wave inversion yields computed tsunami waves systematically too low with respect to observations (on the central Pacific Ocean DART buoy as on the Polynesian tide gauge), the source model established from the surface-wave inversion is more efficient to fit the observations, confirming that the tsunami is sensitive to the low frequency component of the source. Finally we also discuss the modeling of the late tsunami arrivals in Taiohae Bay using several friction coefficients for the sea bottom.  相似文献   

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