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1.
The hydrogen sulfide rich waters of the Black Sea pose a potential danger for the surrounding land regions. The impact of an asteroid exceeding tens of meters in size may cause both a tsunami wave and a catastrophic poisonous gas release in the atmosphere. Some effects of this last phenomenon on the Southern Black Sea coastal regions are evaluated in this paper. The initial surface area of the poisonous cloud depends on asteroid size. The initial thickness of the cloud depends, in addition, on sea depth at impact location. The wind speed plays an important role in H2S cloud dynamics. At 10 m/s wind speed, the cloud margins reach 185 km from the impact location in about 3 h. The maximum distance traveled by the hydrogen sulfide cloud increases by increasing the asteroid size and wind speed. The influence of the impact position on the distance traveled by hydrogen sulfide clouds is rather weak, as long as the seawater depth does not change significantly. The land surface area covered by the H2S cloud generated by a 1,000 m size asteroid ranges between about 6,400 and 12,000 km2. This may affect up to 3,000,000 people. When a 250 m size asteroid is considered, the covered land surface area ranges between about 1,400 and 2,100 km2 and up to 120,000 people may be affected. In case of a 70 m size asteroid, the cloud covers up to 280 km2 of land. This may affect up to about 70,000 people. These evaluations do not include the population of the towns on or near the seashore. A simple methodology to estimate the environmental risks of the potential asteroid impact was proposed. Sites less than 160 km from the impact place are at risk.  相似文献   

2.
The historical tsunamigenic event of 21 July AD 365 destroyed several coastal locations in the Eastern Mediterranean region. The foremost destructive impacts were recorded in Crete and Egypt. The present study re-examines the effect of location, direction, height and time of travel of the tsunami towards the Egyptian coast. Evidently, this tsunamigenic event is related to an earthquake which is identified with a Hellenic Arc subduction-zone event of great magnitude, M > 8, as manifested by up to 9 m uplift in western Crete. The maximum run-up height distribution in the front of the Nile Delta was about 9.5 m in Alexandria, while those of the neighboring cities were 7.1 m, 4.9 m, and 1.9 m at Rashid, Damietta and El-Arish, respectively. Data obtained from this study is essential to evaluate the tsunami hazards along the Egyptian coast.  相似文献   

3.
On 15 July 2009, a Mw 7.8 earthquake occurred off the New Zealand coast, which by serendipitous coincidence occurred while the International Tsunami Symposium was in session in Novosibirsk, Russia. The earthquake generated a tsunami that propagated across the Tasman Sea and was detected in New Zealand, Australia and as far away as the US West coast. Small boats close to the epicenter were placed in jeopardy, but no significant damage was observed despite a measured run-up height of 2.3 m in one of the Sounds in close proximity to the source (Wilson in GNS Science Report 46:62 2009). Peak-to-trough tsunami heights of 55 cm were measured at Southport, Tasmania and a height of 1 m was measured in Jackson Bay, New Zealand. The International Tsunami Symposium provided an ideal venue for illustration of the value of immediate real-time assessment and provided an opportunity to further validate the real time forecasting capabilities with the scientific community in attendance. A number of agencies with responsibility for tsunami forecast and/or warning, such as the NOAA Center for Tsunami Research, the Pacific Tsunami Warning Center, GNS Science in New Zealand, the Australian Bureau of Meteorology and the European Commission Joint Research Centre were all represented at the meeting and were able to demonstrate the use of state of the art numerical models to assess the tsunami potential and provide warning as appropriate.  相似文献   

4.
Energy Decay of the 2004 Sumatra Tsunami in the World Ocean   总被引：1，自引：0，他引：1  
The catastrophic Indian Ocean tsunami generated off the coast of Sumatra on 26 December 2004 was recorded by a large number of tide gauges throughout the World Ocean. This study uses gauge records from 173 sites to examine the characteristics and energy decay of the tsunami waves from this event in the Indian, Atlantic and Pacific oceans. Findings reveal that the decay (e-folding) time of the tsunami wave energy within a given oceanic basin is not uniform, as previously reported, but depends on the absorption characteristics of the shelf adjacent to the coastal observation site and the time for the waves to reach the site from the source region. In general, the decay times for island and open-ocean bottom stations are found to be shorter than for coastal mainland stations. Decay times for the 2004 Sumatra tsunami ranged from about 13 h for islands in the Indian Ocean to 40–45 h for mainland stations in the North Pacific.  相似文献   

5.
Sumatra tsunami: lessons from modeling   总被引：1，自引：0，他引：1  
The need for the combination of seismic data with real-time wave height information for an effective prediction of tsunami impact is emphasized in the paper. A preliminary, but comprehensive study of arrival times, wave heights and run-up values at a number of locations and tide gage stations throughout the Indian Ocean seaboard is presented. Open ocean wave height data from satellite observations are analyzed and used in the reconstruction of a tsunami source mechanism for the December 26, 2004 event. The reconstructed source is then used to numerically estimate tsunami impact along the Indian Ocean seaboard, including wave height, and arrival times at 12 tide gage stations, and inundation at 3 locations on the coast of India. The December 2004, as well as the March 28, 2005 tsunamis are investigated and their differences in terms of tsunami generation are analyzed and presented as a clear example of the need for both, seismic and real-time tsunami data for a reliable tsunami warning system in the Indian Ocean.  相似文献   

6.
The role of sector collapse in the generation of catastrophic volcanigenic tsunami has become well understood only recently, in part because of the problems in the preservation and recognition of tsunami deposits. Tinti et al. [Tinti, S., Bortolucci, E., Romagnoli, C., 2000. Computer simulations of tsunamis due to sector collapse at Stromboli, Italy. J. Volcanol. Geotherm. Res. 96, 103–128] modeled a tsunami produced by the c. 5,000 years BP collapse of the Sciara del Fuoco on the island volcano Stromboli. Although deposits associated with this event are generally lacking on the island, volcaniclastic breccias on the SE side of the island extending to an elevation above 120 m a.s.l. may have been generated by this tsunami. Deposits above 100 m are dominated by coarse breccias comprising disorganized, poorly sorted, nonbedded, angular to subangular lava blocks in a matrix of finer pyroclastic debris. These breccias are interpreted as a water-induced mass flow, possibly a noncohesive debris flow, generated as colluvial material on steep slopes was remobilized by the return flow of the tsunami wave, the run-up of which reached an elevation exceeding 120 m a.s.l. Finer breccias of subrounded to rounded lava blocks cropping out at 15 m a.s.l. are similar to modern high-energy beach deposits and are interpreted as beach material redeposited by the advancing tsunami wave. The location of these deposits matches the predicted location of the maximum tsunami wave amplitude as calculated by modeling studies of Tinti et al. [Tinti, S., Bortolucci, E., Romagnoli, C., 2000. Computer simulations of tsunamis due to sector collapse at Stromboli, Italy. J. Volcanol. Geotherm. Res. 96, 103–128]. Whereas the identification and modeling of paleo-tsunami events is typically based on the observation of the sedimentary deposits of the tsunami run-up, return flow may be equally or more important in controlling patterns of sedimentation.  相似文献   

7.
In this paper,we present a numerical simulation of the propagation of a tsunami in the East China Sea,which might be induced by a hypothetical M8.5 earthquake in Okinawa Trough. Our results show that the initial maxi-mum wave height of tsunami could reach as high as 4.3 m for the hypothetical earthquake. It would take 3.5～4 hours for the tsunami to propagate to the coast of Zhejiang Province,and 7～8 hours to the near-shore of Shanghai. The peak tsunami height could be up to about 2 m in the coast of Zhejiang Province. Based on the numerical ex-periments,we plot the arrival time contours of tsunami in East China Sea and time history curves on the three ob-servational stations,and discussed the significance of the pre-analysis.  相似文献   

8.
We analyzed sea level data from a set of tide gauge stations located in the central and western Mediterranean Sea, that recorded the tsunami generated by the Mw 6.8 Boumerdès earthquake striking the coast of Algeria on May 21, 2003. This earthquake caused more than 2200 victims and thousands of injured. The causative fault was located a few kilometers offshore and during the rupture a tsunami was triggered. Waves were felt along a large part of the western and northern Mediterranean coasts, and in the Balearic islands waves higher that 2 m were measured. In this paper we analyze a more complete tidal data set, with respect to previous studies, now consisting of 22 tidal stations located in Italy, France and Spain. To characterize the change of the tidal signal at each station we used the Empirical Mode Decomposition (EMD). By means of this technique, which is suitable to analyze and to characterize the dynamical behavior of non-stationary time series, we provide a precise measurement of the arrival times and amplitudes at the tidal stations and identify how this tsunami affected the principal and long term tidal components. Our findings improve previous results for this earthquake, since they allow the detection of significant amplitude fluctuations associated with the tsunami in the majority of stations, including the farthest ones.  相似文献   

9.
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   

10.
In the last 15 years there have been 16 tsunami events recorded at tide stations on the Pacific Coast of Canada. Eleven of these events were from distant sources covering almost all regions of the Pacific, as well as the December 26, 2004 Sumatra tsunami in the Indian Ocean. Three tsunamis were generated by local or regional earthquakes and two were meteorological tsunamis. The earliest four events, which occurred in the period 1994–1996, were recorded on analogue recorders; these tsunami records were recently re-examined, digitized and thoroughly analysed. The other 12 tsunami events were recorded using digital high-quality instruments, with 1-min sampling interval, installed on the coast of British Columbia (B.C.) in 1998. All 16 tsunami events were recorded at Tofino on the outer B.C. coast, and some of the tsunamis were recorded at eight or more stations. The tide station at Tofino has been in operation for 100 years and these recent observations add to the dataset of tsunami events compiled previously by S.O. Wigen (1983) for the period 1906–1980. For each of the tsunami records statistical analysis was carried out to determine essential tsunami characteristics for all events (arrival times, maximum amplitudes, frequencies and wave-train structure). The analysis of the records indicated that significant background noise at Langara, a key northern B.C. Tsunami Warning station located near the northern end of the Queen Charlotte Islands, creates serious problems in detecting tsunami waves. That station has now been moved to a new location with better tsunami response. The number of tsunami events observed in the past 15 years also justified re-establishing a tide gauge at Port Alberni, where large tsunami wave amplitudes were measured in March 1964. The two meteorological events are the first ever recorded on the B.C. coast. Also, there have been landslide generated tsunami events which, although not recorded on any coastal tide gauges, demonstrate, along with the recent investigation of a historical catastrophic event, the significant risk that landslide generated tsunami pose to coastal and inland regions of B.C.  相似文献   

11.
—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   

12.
— Simulation of tsunami propagation and runup of the 1998 Papua New Guinea (PNG) earthquake tsunami using the detailed bathymetry measured by JAMSTEC and adding bathymetric data at depths less than 60 m is carried out, reproducing the tsunami energy focus into Warapu and Arop along the Sissano Lagoon. However, the computed runup heights in the lagoon are still lower than those measured. Even if the error in estimating the fault parameters is taken into consideration, computational results are similar. Analysis by the wave ray method using several scenarios of the source size of the tsunami and location by the wave ray method suggests that a source characterized by small size in water 1,000-m deep approximately 25 km offshore the lagoon, best fits the arrival determined from the interviews with eyewitnesses. A two-layer numerical model simulating the interaction of the tsunami with a landslide is employed to study the behavior of a landslide-generated tsunami with different size sand depths of the initial slide just outside the lagoon. A landslide model with a volume of 4–8 × 109 m3 is selected as the best in order to reproduce the distribution of the measured tsunami runup in the lagoon. The simulation of a tsunami generated in two stages, fault and landslide, could show good agreement with the runup heights and distribution of the arrival time, but a time gap of around 10 minutes remains, suggesting that a tsunami generated by the mainshock at 6:49 PM local time is too small for people to notice, and the following tsunami triggered by landslide or mass movement near the lagoon about ten minutes after the mainshock attacked the coast and caused the huge damage.  相似文献   

13.
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   

14.
Several independent indicators imply a high probability of a great (M > 8) earthquake rupture of the subduction megathrust under the Mentawai Islands of West Sumatra. The human consequences of such an event depend crucially on its tsunamigenic potential, which in turn depends on unpredictable details of slip distribution on the megathrust and how resulting seafloor movements and the propagating tsunami waves interact with bathymetry. Here we address the forward problem by modelling about 1000 possible complex earthquake ruptures and calculating the seafloor displacements and tsunami wave height distributions that would result from the most likely 100 or so, as judged by reference to paleogeodetic data. Additionally we carry out a systematic study of the importance of the location of maximum slip with respect to the morphology of the fore-arc complex. Our results indicate a generally smaller regional tsunami hazard than was realised in Aceh during the December 2004 event, though more than 20% of simulations result in tsunami wave heights of more than 5 m for the southern Sumatran cities of Padang and Bengkulu. The extreme events in these simulations produce results which are consistent with recent deterministic studies. The study confirms the sensitivity of predicted wave heights to the distribution of slip even for events with similar moment and reproduces Plafker's rule of thumb. Additionally we show that the maximum wave height observed at a single location scales with the magnitude though data for all magnitudes exhibit extreme variability. Finally, we show that for any coastal location in the near field of the earthquake, despite the complexity of the earthquake rupture simulations and the large range of magnitudes modelled, the timing of inundation is constant to first order and the maximum height of the modelled waves is directly proportional to the vertical coseismic displacement experienced at that point. These results may assist in developing tsunami preparedness strategies around the Indian Ocean and in particular along the coasts of western Sumatra.  相似文献   

15.
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.  相似文献   

16.
High-frequency (HF) surface wave radars provide the unique capability to continuously monitor the coastal environment far beyond the range of conventional microwave radars. Bragg-resonant backscattering by ocean waves with half the electromagnetic radar wavelength allows ocean surface currents to be measured at distances up to 200 km. When a tsunami propagates from the deep ocean to shallow water, a specific ocean current signature is generated throughout the water column. Due to the long range of an HF radar, it is possible to detect this current signature at the shelf edge. When the shelf edge is about 100 km in front of the coastline, the radar can detect the tsunami about 45 min before it hits the coast, leaving enough time to issue an early warning. As up to now no HF radar measurements of an approaching tsunami exist, a simulation study has been done to fix parameters like the required spatial resolution or the maximum coherent integration time allowed. The simulation involves several steps, starting with the Hamburg Shelf Ocean Model (HAMSOM) which is used to estimate the tsunami-induced current velocity at 1 km spatial resolution and 1 s time step. This ocean current signal is then superimposed to modelled and measured HF radar backscatter signals using a new modulation technique. After applying conventional HF radar signal processing techniques, the surface current maps contain the rapidly changing tsunami-induced current features, which can be compared to the HAMSOM data. The specific radial tsunami current signatures can clearly be observed in these maps, if appropriate spatial and temporal resolution is used. Based on the entropy of the ocean current maps, a tsunami detection algorithm is described which can be used to issue an automated tsunami warning message.  相似文献   

17.
The velocity structure of the Black Sea lithosphere has been studied using the local seismic tomography method based on the Backus-Gilbert approach and applied for a quite large amount of seismological data. As seismic sources, we used the earthquakes that occurred within the Black Sea and adjoining regions and generated seismic waves recorded by seismic stations around the Black Sea. This yielded information on the 3D distribution of P-waves within the most heterogeneous and poorly investigated uppermost layer of the Black Sea region (down to a depth of 60 km). The interpretation of these results, together with new data on the velocity structure of the crust of the Black Sea led to the conclusion about the different lithosphere beneath the West and the East Black Sea Basins. This can be explained by origination of the depressions in the western and eastern parts of the Black Sea at different microplates and by specific features in their development at rifting and post-rifting stages.  相似文献   

18.
The present study focuses on evaluation of the maximum and minimum water levels caused by tsunamis as risk factors for operation and management at nuclear power facilities along the coastal area of Japan. Tsunamis generated by submarine earthquakes are examined, basing literature reviews and databases of information on historical tsunami events and run-up heights. For simulation of water level along the coast, a numerical calculation system should be designed with computational regions covering a particular site. Also the calculation system should be verified by comparison of historical and calculated tsunami heights. At the beginning of the tsunami assessment, the standard faults, their locations, mechanisms and maximum magnitudes should be carefully estimated by considering historical earthquake-induced tsunamis and seismo-tectonics at each area. Secondly, the range of errors in the model parameters should be considered since earthquakes and tsunamis are natural phenomena that involve natural variability as well as errors in estimating parameters. For these reasons, uncertainty-induced errors should be taken into account in the process of tsunami assessment with parametric study of the tsunami source model. The element tsunamis calculated by the standard fault models with the errors would be given for the design. Then, the design tsunami can be selected among the element tsunamis with the most significant impact, maximum and minimum water levels, on the site, bearing in mind the possible errors in the numerical calculation system. Finally, the design tsunami is verified by comparison with the run-up heights of historical tsunamis, ensuring that the design tsunami is selected as the highest of all historical and possible future tsunamis at the site.  相似文献   

19.
The 1883 eruption of Augustine Volcano produced a tsunami when a debris avalanche traveled into the waters of Cook Inlet. Older debris avalanches and coeval paleotsunami deposits from sites around Cook Inlet record several older volcanic tsunamis. A debris avalanche into the sea on the west side of Augustine Island ca. 450 years ago produced a wave that affected areas 17 m above high tide on Augustine Island. A large volcanic tsunami was generated by a debris avalanche on the east side of Augustine Island ca. 1600 yr BP, and affected areas more than 7 m above high tide at distances of 80 km from the volcano on the Kenai Peninsula. A tsunami deposit dated to ca. 3600 yr BP is tentatively correlated with a southward directed collapse of the summit of Redoubt Volcano, although little is known about the magnitude of the tsunami. The 1600 yr BP tsunami from Augustine Volcano occurred about the same time as the collapse of the well-developed Kachemak culture in the southern Cook Inlet area, suggesting a link between volcanic tsunamis and prehistoric cultural changes in this region of Alaska.  相似文献   

20.
— On the evening of 17 July 1998, on th e Aitape Coast of Papua New Guinea, a strongly felt earthquake was followed some 10–25 minutes later by a destructive tsunami. The tsunami comprised three waves, each estimated to be about 4 m high. The second of the three waves rose to a height of 10–15 m above sea level after it had crossed the shoreline and caused most damage. Maximum wave heights and the greatest damage were recorded along a 14-km sector of coast centered on Sissano Lagoon. In this sector the wavefronts moved from east to west along the coast; all structures were destroyed, and in the two main villages 20–40 percent of the population was killed. Partial destruction extended 23 km to the southeast and 8 km to the northwest, and effects of the tsunami were felt as far as 250 km to the west–northwest, beyond the international border. More than 1600 people are known to have died, with some estimates as high as 2200; 1000 were seriously injured, and 10,000 survivors were displaced. This paper presents information from interviews with eye-witnesses and from mapping of damage and inundation, and includes new information on the height, shape and timing of the waves; on the possible escape of petroleum and other gases from beneath the seafloor before and during the tsunami; on unusual sound effects that preceded the waves, and lighting effects that followed; on possible deep circulation (to 250 m) of sea water in the waves; on subsidence of the order of 50–70 cm at the coastal sand barrier; and on the resilience and potential protective capacity of certain species of trees. Eye-witness accounts indicate that the tsunami reached the shore at between 09:00 and 09:08 UT, which is earlier than is proposed in published models of the timing and location of the source of the tsunami.  相似文献   

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