排序方式： 共有3条查询结果，搜索用时 0 毫秒
1
1.
Shigehiro Fujino Hajime Naruse Dan Matsumoto Norihiko Sakakura Apichart Suphawajruksakul Thanawat Jarupongsakul 《Island Arc》2010,19(3):389-398
Measurements of thickness and grain size along flow‐parallel transects across onshore deposits of the 2004 Indian Ocean tsunami revealed macroscopic horizontal variations and provided new insights into tsunami sedimentation. The tsunami caused severe erosion of beaches, river mouths, and the shallow seafloor along the coast of southwestern Thailand and supplied sufficient sediment to deposit a kilometer‐wide blanket of sand on the land surface. The tsunami deposits generally fine landward with some fluctuations caused by local entrainment and settlement of sediments. Sediments of medium and fine sand are restricted to a few hundreds of meters inland from their source, whereas finer grained sediments were suspended longer and deposited 1 km or more inland. Although the thickness of the tsunami deposits is strongly influenced by local topography, they generally thin landward. In areas of low‐relief topography, the rate of landward thinning is exponential and reflects the dominance of sediment supply to nearshore areas over that to areas farther inland. 相似文献
2.
Katsuto Uehara Pramot Sojisuporn Yoshiki Saito Thanawat Jarupongsakul 《地球表面变化过程与地形》2010,35(14):1701-1711
Seasonal variation in seabed elevation in the muddy intertidal zone of the Chao Phraya River delta, an area of serious coastal erosion for 40 years, was assessed using information on waves and tides predicted by numerical simulations. The study area is under the influence of the Southeast Asian monsoon climate and lies in the innermost part of a sheltered gulf, across which a low‐gradient slope has developed. Observations, aimed at evaluating the effectiveness of a prototype breakwater on mitigating coastal erosion, indicated that the seasonal variation in the seabed elevation, typically about 30 cm, was caused primarily by seasonal changes in wave direction and height. The breakwater seems to have contributed to a net rise in the seabed level at sites behind the structure. Seabed erosion was most apparent during the northeast monsoon, when waves are weak. Erosion under this low wave energy state was attributed to the combined effect of wave breaking and the low tidal level. A difference in the observed seabed accretion rate between the transitional intermonsoon period and the succeeding southwest monsoon period was attributed to the direction of the wave energy flux; offshore sediments seem to have been supplied efficiently to the study area by waves during the transitional period. Another potential cause of seabed erosion and accretion during the wet southwest monsoon season was the discharge of water and sediments from local canals associated with intense tropical rainfall; this discharge seems to be linked to land use in the coastal area. The results of this study show the importance of monitoring across‐shore sediment transport for better understanding of coastal erosion processes. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
Hajime Naruse Shigehiro Fujino Apichart Suphawajruksakul Thanawat Jarupongsakul 《Island Arc》2010,19(3):399-411
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. 相似文献
1