日本地球惑星科学連合2018年大会

講演情報

[EJ] Eveningポスター発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG58] 沈み込み帯へのインプットを探る:海溝海側で生じる過程の影響

2018年5月23日(水) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:山野 誠(東京大学地震研究所)、森下 知晃(金沢大学理工研究域自然システム学系)、藤江 剛(海洋研究開発機構)

[SCG58-P06] IODP Expedition 375: Hikurangi Subduction Margin – first chronostratigraphic constraints derived from shipboard palaeomagnetic analyses

*Annika Greve1Xuesen Li6Katerina Petronotis3Martin Crundwell2Claire Shepherd2Adam Woodhouse7Phil Barnes4Laura Wallace2Demian Saffer5the IODP expedition 375 shipboard scientists (1.Research and Development Center for Ocean Drilling Science, Japan Agency for Marine-Earth Science and Technology、2.GNS Science、3.International Ocean Discovery Program, Texas A&M University、4.National Institute of Water and Atmospheric Research (NIWA)、5.Department of Geosciences, Pennsylvania State University、6.College of Earth Science, Guilin University of Technology、7.School of Earth and Environment, University of Leeds)

キーワード:IODP, Hikurangi margin, subduction, magnetostratigraphy, stratigraphy, palaeomagnetism

The Hikurangi margin, located offshore the eastern coast of the Central North Island in New Zealand is the site of oblique convergence between the Pacific and Australian Plates. It has recently received a considerable amount of public and scientific attention due to periodic re-occurrence of so-called slow-slip or low frequency earthquakes, which are believed to be triggered by the slow release of strain.

Subduction initiation along the Hikurangi margin is believed to date back to ca. 20 - 25 Myrs ago. The entire margin is known to have experienced significant clockwise rotation, which was probably initiated approximately 2 Myrs ago in association with the onset of subduction of the buoyant and Mesozoic aged Hikurangi Plateau at its southern end, which resulted in coupling between the underlying Pacific and overriding Australian plates.

Partitioning between margin normal and parallel strain significantly affected the whole-sale evolution of the Central North Island and the geometry of the accretionary complex. The onshore expressions of the Hikurangi margin are generally well studied. In contrast, to date all studies of the accretionary history and structure of the offshore margin were limited to the interpretations of active and passive source seismic surveys, thus providing little absolute chronological information.

Expedition 375 of the International Ocean Discovery Program (March & April, 2018) targets four drill sites along a transect that encompasses the upper slope, frontal thrust and sediments of the incoming plates with inferred ages spanning the Cenozoic.

In this presentation I will briefly introduce the key expedition objectives and achievements. I will then focus on the chronostratigraphic constraints provided from the shipboard palaeomagnetic investigations. The results may provide a first insight into the accretionary and deformation history along the upper slope, timing of seismic slip along a major frontal thrust fault and depositional history of the Pacific Plate.

Highlights and pitfalls of the palaeo- and rock magnetic analyses will be outlined and avenues for further research discussed.