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排序方式: 共有546条查询结果,搜索用时 15 毫秒
31.
Katsuyuki Abe 《Pure and Applied Geophysics》1995,144(3-4):735-745
The Hokkaido-Nansei-Oki earthquake (M
w
7.7) of July 12, 1993, is one of the largest tsunamigenic events in the Sea of Japan. The tsunami magnitudeM
t
is determined to be 8.1 from the maximum amplitudes of the tsunami recorded on tide gauges. This value is larger thanM
w
by 0.4 units. It is suggested that the tsunami potential of the Nansei-Oki earthquake is large forM
w
. A number of tsunami runup data are accumulated for a total range of about 1000 km along the coast, and the data are averaged to obtain the local mean heightsH
n
for 23 segments in intervals of about 40 km each. The geographic variation ofH
n
is approximately explained in terms of the empirical relationship proposed byAbe (1989, 1993). The height prediction from the available earthquake magnitudes ranges from 5.0–8.4 m, which brackets the observed maximum ofH
n
, 7.7 m, at Okushiri Island. 相似文献
32.
We report on calculations of the on-shore run-up of waves that might be generated by the impact of subkilometre asteroids into the deep ocean. The calculations were done with the COULWAVE code, which models the propagation and shore-interaction of non-linear moderate- to long-wavelength waves ( kh < π) using the extended Boussinesq approximation. We carried out run-up calculations for several different situations: (1) laboratory-scale monochromatic wave trains onto simple slopes; (2) 10–100 m monochromatic wave trains onto simple slopes; (3) 10–100 m monochromatic wave trains onto a compound slope representing a typical bathymetric profile of the Pacific coast of North America; (4) time-variable scaled trains generated by the collapse of an impact cavity in deep water onto simple slopes and (5) full-amplitude trains onto the Pacific coast profile. For the last case, we also investigated the effects of bottom friction on the run-up. For all cases, we compare our results with the so-called 'Irribaren scaling': The relative run-up R / H 0 =ξ= s ( H 0 / L 0 )−1/2 , where the run-up is R , H 0 is the deep-water waveheight, L 0 is the deep-water wavelength, s is the slope and ξ is a dimensionless quantity known as the Irribaren number. Our results suggest that Irribaren scaling breaks down for shallow slopes s ≤ 0.01 when ξ < 0.1 − 0.2 , below which R / H 0 is approximately constant. This regime corresponds to steep waves and very shallow slopes, which are the most relevant for impact tsunami, but also the most difficult to access experimentally. 相似文献
33.
MICHAEL BIRD SUSAN COWIE REA HAWKES† BEN HORTON† COLIN MACGREGOR JIN EONG ONG‡ AILEEN TAN SHAU HWAI§ TEH TIONG SA¶ ZULFIGAR YASIN§ 《The Geographical journal》2007,173(2):103-117
We report the results of a study of the physical characteristics and socio-economic impacts of the Indian Ocean Tsunami of 26 December 2004 on the tourist island of Langkawi, Malaysia. In comparison with many other locations struck by the tsunami, the immediate physical and socio-economic impacts in Langkawi were relatively minor. A detailed survey of the watermark and ground elevations was undertaken in the worst affected area between Sungei Kuala Teriang and Sungei Kuala Melaka. Here, the tsunami reached a maximum elevation of 4.29 m as it crossed the coast, with a maximum flow depth of 2.0 m and a very consistent run-up elevation relative to mean sea level of 300 ± 10 cm. The tsunami inundated inshore areas for 300 m and penetrated inland along creeks for 500–1000 m. Structural damage to buildings was confined to within 50–150 m of the shoreline where about 10% of the houses were completely destroyed and 60–70% suffered significant structural damage. Damage was particularly severe in areas where there was no engineered coastal protection, but while coastal revetments did provide enhanced protection for houses at the waterfront, the coastline in the study area appeared to be more heavily impacted than elsewhere in Langkawi because wave energy was focused on the area by offshore breakwaters built to protect the Langkawi port and airport. Emergency response after the tsunami was rapid and efficient but would have been improved if the local police station had not been rendered inoperative by the first wave, and if a mechanism had been in place to ensure that informal advance warnings transmitted between Phuket (Thailand), Langkawi and Penang (Malaysia) by tourist operators could have been more widely disseminated. 相似文献
34.
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. 相似文献
35.
Logic-tree Approach for Probabilistic Tsunami Hazard Analysis and its Applications to the Japanese Coasts 总被引:2,自引:0,他引:2
Tadashi Annaka Kenji Satake Tsutomu Sakakiyama Ken Yanagisawa Nobuo Shuto 《Pure and Applied Geophysics》2007,164(2-3):577-592
For Probabilistic Tsunami Hazard Analysis (PTHA), we propose a logic-tree approach to construct tsunami hazard curves (relationship
between tsunami height and probability of exceedance) and present some examples for Japan for the purpose of quantitative
assessments of tsunami risk for important coastal facilities. A hazard curve is obtained by integration over the aleatory
uncertainties, and numerous hazard curves are obtained for different branches of logic-tree representing epistemic uncertainty.
A PTHA consists of a tsunami source model and coastal tsunami height estimation. We developed the logic-tree models for local
tsunami sources around Japan and for distant tsunami sources along the South American subduction zones. Logic-trees were made
for tsunami source zones, size and frequency of tsunamigenic earthquakes, fault models, and standard error of estimated tsunami
heights. Numerical simulation rather than empirical relation was used for estimating the median tsunami heights. Weights of
discrete branches that represent alternative hypotheses and interpretations were determined by the questionnaire survey for
tsunami and earthquake experts, whereas those representing the error of estimated value were determined on the basis of historical
data. Examples of tsunami hazard curves were illustrated for the coastal sites, and uncertainty in the tsunami hazard was
displayed by 5-, 16-, 50-, 84- and 95-percentile and mean hazard curves. 相似文献
36.
Aoibheann A. Kilfeather Jeffrey J. Blackford Jaap J. M. van der Meer 《Pure and Applied Geophysics》2007,164(2-3):509-525
Tsunami deposits are provisionally distinguished in the field on the basis of anomalous sand horizons, fining-up and fining-landward,
coupled with organic-rich, fragmented `backwash' sediments. In this paper, micromorphological features of a sediment sequence
previously interpreted as being of tsunami origin are described. These characteristics are shown to be consistent with the
macro-scale features used elsewhere, but show additional details not seen in standard stratigraphies, including possible evidence
for individual waves, possibly wave-magnitude progression, organic fragment alignment and intraclast microstructures. Although
replication and more complete studies are needed, this analysis confirms the identification of a tsunami in Willapa Bay in
ca.1700 AD, while demonstrating a widely applicable technique for confirming or refuting possible tsunami deposits. 相似文献
37.
Kuniaki Abe 《Pure and Applied Geophysics》2007,164(2-3):453-463
We identified a phase representing the source length of tsunami's in the tide gauge records around Japan. This phase was observed
at tide stations, located in the direction of the long axis of the sources, for four large tsunamis: 1964 Niigata, 1968 Tokachi-oki,
1983 Nihonkaichubu, and 1993 Hokkaido-nanseioki. The phase consists of two continuous crests starting as the initial arrival
and has a time length of 15–47 minutes. This is the time required to propagate across the source area along the long axis.
Strong evidence that the phase is generated at the source is the good correlation between waveform observed at one side and
time-inversed waveform at another side. The correlation results from the instantaneous generation of the source. The source
lengths of 74–254 km were obtained under an assumption of sea depths at the sources and verified to coincide with ones within
a relative error of 15% that were previously obtained by other methods. 相似文献
38.
We extend to the regional field of distances the procedure of one-station estimation of seismic moments using the mantle magnitudeM
m, as introduced earlier in the case of teleseismic events. A theoretical analysis of the validity of the asymptotic expansion of normal modes in terms of surface waves, which was used in the development ofM
m, upholds the validity of the algorithm for distances as short as 1.5°. This is confirmed by the analysis of a dataset of 149 GEOSCOPE records obtained at distances ranging from 1.5 to 15°, from earthquakes with moments between 1024 and 2.5×1027 dyn-cm. The performance ofM
m as measured in terms of average residual with respect to published values ofM
0, and standard deviation of the residuals, is not degraded in this distance range, with respect to the teleseismic case. This indicates that the mantle magnitudeM
mcan be reliably used at regional distances, notably for tsunami warning applications. 相似文献
39.
Taku Tada Yoshinobu Tsuji Masahito Tsukamoto Yoshikazu Ueno Masayuki Kawashima Takashi Egawa Yasuhiro Yamazaki 《Pure and Applied Geophysics》1992,138(2):309-322
We carried out observations of sea-level fluctuations simultaneously at three stations on the coast of Heda Bay, Honshu, Japan, using supersonic-type water level gauges controlled by a personal computer. Analyses of the obtained data showed predominant spectral peaks at periods of 7.6, 2.0 and 1.3 minutes for all three stations. Comparison of the observed data with numerically calculated normal oscillation modes of the bay indicates that these three spectral peaks correspond to the theoretical first, third and seventh normal modes of the basin respectively, judging from the results of cross-spectral analyses. The reason for the absence of the remaining normal modes, especially of the second or the lateral first mode of the basin, is briefly considered. 相似文献
40.