Mechanisms of Shore Platform Formation on the Southeastern Coast of the Izu Peninsula, Japan
1978; University of Chicago Press; Volume: 86; Issue: 2 Linguagem: Inglês
10.1086/649675
ISSN1537-5269
Autores Tópico(s)Earthquake and Tsunami Effects
ResumoShore platforms incised into Tertiary volcanic rocks on the southeastern coast of the Izu peninsula, facing the Pacific Ocean, show regional differences in their elevation: the platforms on the promontories are higher than those in the coves or the areas behind islands. The level of the former varies from place to place, while that of the latter is approximately constant. Prior to the investigation of the mechanisms forming the platforms, the latest local crustal movement was examined. The study area proved to have been uplifted about 1.5 m due to the earthquake of 1703. The field study suggested that the platforms had already been formed at the time of this tectonic uplift. Therefore, the formative mechanism was explored under the pre-uplift conditions. This exploration was done by focussing on the nearshore wave dynamics. The result showed that the platforms at the headlands were produced by the action of breaking waves occurring in front of the bluff during stormy periods, and their original elevation was determined by the height at which breaking waves operated; while the platforms in the sheltered areas were developed by the interaction of broken waves and rock weathering, and their elevation was controlled by the level of permanent saturation.
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