Active rifting structures in iheya graben and adjacent area of the mid-okinawa trough observed through seismic reflection surveys

Fumihiko Ikegami, Takeshi Tsuji, Hidenori Kumagai, Jun Ichiro Ishibashi, Ken Takai

Research output: Chapter in Book/Report/Conference proceedingChapter

2 Citations (Scopus)

Abstract

The mid-Okinawa Trough is recognized as an area with extensive volcanism and hydrothermal activity. The Iheya Graben is a depression in the mid-Okinawa Trough, extending approximately 100 km in an ENE-WSW strike. The graben lies 200 m below the surrounding flat-surfaced trough floor (from _1,400 to _1,600 m below sea level). The latest seismic profiles in the western Iheya Graben and adjacent areas reveal numerous normal faults, possibly in association with the rifting activity of the Okinawa Trough. The faulting of the Iheya Graben is non-listric syn-depression faulting, in contrast with dense listric faulting of the adjacent trough floor. The faulting in both areas consists of numerous seafloor-reaching active faults; however, recent activity is concentrated within the Iheya Graben. Non-listric faulting in the Iheya Graben shapes its present structure with large displacements. The displacements and fault propagations indicate the depression of the Iheya Graben was created with an abrupt flexural subsidence followed by extension with normal faulting. The event occurred largely before the formation of the overlying Iheya Ridge, which was reported to be at least 0.2 Ma. Such a significant event may be related to the present extensive volcanism in the region by means of rifting tectonics and magmatism. Keywords.

Original languageEnglish
Title of host publicationSubseafloor Biosphere Linked to Hydrothermal Systems
Subtitle of host publicationTAIGA Concept
PublisherSpringer Japan
Pages361-368
Number of pages8
ISBN (Electronic)9784431548652
ISBN (Print)9784431548645
DOIs
Publication statusPublished - Jan 1 2015

All Science Journal Classification (ASJC) codes

  • Earth and Planetary Sciences(all)

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    Ikegami, F., Tsuji, T., Kumagai, H., Ishibashi, J. I., & Takai, K. (2015). Active rifting structures in iheya graben and adjacent area of the mid-okinawa trough observed through seismic reflection surveys. In Subseafloor Biosphere Linked to Hydrothermal Systems: TAIGA Concept (pp. 361-368). Springer Japan. https://doi.org/10.1007/978-4-431-54865-2_28