10:00 AM - 10:15 AM
[HGM03-07] Relation between fore-arc topography and slab configuration in Japan
Keywords:large-scale landform, slab configuration, dislocation model
It has not been easy to clarify the causes of topographic evolution. Even in Japan, where extensive studies on topography has been done, the causes of topographic evolution have not been well understood for most cases except for limited examples, such as the formation of the Hidaka Mountains and the collision of the Izu Peninsula, which are direct consequences of plate tectonics.
By the way, we can notice that depression areas in the fore-arc of Japan, such as the Hidaka Trough, the Kanto Plain, the Nobi Plain, the Kii Strait, and the Bungo Channel, well correspond to the locations where the descending slab has a ridge and/or a bending shape along the trench.
Matsu'ura & Sato (1989) developed a dislocation model for plate subduction, with which we can well understand the formation of characteristic topography of subduction zones, island-arc high, trench low, and outer-rise high (Fukahata & Matsu'ura 2016), and observed free-air gravity anomaly patterns in and around Japan (Hashimoto et al. 2004).
In this study, we show that numerical simulation based on the dislocation model for plate subduction well reproduces significant subsidence around a bend of the trench axis and/or above a ridge of the descending slab. Based on the model, we can now understand the causes of the above mentioned topography. The Hidaka Trough and the Kanto Plain locate at the junctions of the Kuril and the Japan trenches, and the Japan and Izu-Bonin trenches, respectively. The ridges of the Philippine Sea slab results in the depression areas of the Nobi Plain, the Kii Strait, and the Bungo Channel.
Because dislocation sources are given along the plate interface, the results of numerical simulation can be reasonably explained by mass deficit in the overriding plate, which is coupled with mass excess in the descending slab. The mass excess in the descending slab can be understood by an analogy of a tablecloth; when a tablecloth, which mimics a slab, is put on a square table, it always has an excess surface area down the corner of the table.
By the way, we can notice that depression areas in the fore-arc of Japan, such as the Hidaka Trough, the Kanto Plain, the Nobi Plain, the Kii Strait, and the Bungo Channel, well correspond to the locations where the descending slab has a ridge and/or a bending shape along the trench.
Matsu'ura & Sato (1989) developed a dislocation model for plate subduction, with which we can well understand the formation of characteristic topography of subduction zones, island-arc high, trench low, and outer-rise high (Fukahata & Matsu'ura 2016), and observed free-air gravity anomaly patterns in and around Japan (Hashimoto et al. 2004).
In this study, we show that numerical simulation based on the dislocation model for plate subduction well reproduces significant subsidence around a bend of the trench axis and/or above a ridge of the descending slab. Based on the model, we can now understand the causes of the above mentioned topography. The Hidaka Trough and the Kanto Plain locate at the junctions of the Kuril and the Japan trenches, and the Japan and Izu-Bonin trenches, respectively. The ridges of the Philippine Sea slab results in the depression areas of the Nobi Plain, the Kii Strait, and the Bungo Channel.
Because dislocation sources are given along the plate interface, the results of numerical simulation can be reasonably explained by mass deficit in the overriding plate, which is coupled with mass excess in the descending slab. The mass excess in the descending slab can be understood by an analogy of a tablecloth; when a tablecloth, which mimics a slab, is put on a square table, it always has an excess surface area down the corner of the table.