Magnetic anisotropies for tsunami deposits: application to the 3.11
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Date
2013-05-24
Journal Title
Journal ISSN
Volume Title
Publisher
Japan Geoscience Union
Abstract
Tsunami deposits consist of well-sorted fine sand intercalating with non-marine black organic mud. It is difficult to reveal
a transport direction of the deposit if the deposit showed no sedimentary fabrics,such as ripples. The proxy of anisotropy of
magnetic susceptibility (AMS) appears to be a promising tool for the study of flow fabrics in recent-tsunami deposits such as
Sumatra tsunami (Wassmer et al. 2010). The AMS fabric might allow us to reconstruct transport directions of unconsolidated
tsunami sediments during emplacement because AMS provides a cryptic alignment of ferromagnetic and paramagnetic minerals.
Such cryptic minerals, such as magnetite or phyllosilicate minerals, would behave as a different emplacement mode in a different
hydrodynamic condition. In the AMS fabrics of volcanic rocks, there are large discrepancies between the magnetic lineation
and the framework-forming silicate linear fabric. This suggests that the uncorroborated use of bulk AMS to detect flow fabric in tsunami deposits has risks. In this article, we show that the anisotropy of anhysteretic remanent magnetization (AARM) may resolve the difficulties. The combination of inundation eye-witness, SEM, AMS, and AARM confirms the flow pattern of recentand
paleo-tsunami deposits from the geoslicer sampleing at Rikuzen-Takata city, Japan during 2011, 11th March Tohoku tsunami.
We determined if the sandy deposits are of tsunami from these magnetic anisotropies. © 2013, Japan Geoscience Union.
Description
Keywords
Tsunamis, Sand, Ferromagnetic materials, Japan, Fabrication, Deposits
Citation
Kon, S., Nakamura, N., Goto, K., Sugawara, D., Iijima, Y., Chagué-Goff, C., & Goff, J. (May). Magnetic anisotropies for tsunami deposits: Application to the 3.11. Paper presented at the Japan Geoscience Union Meeting, May 19-24, 2013, Makuhari, Chiba, Japan.