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The Role of Fluid‐Related Heterogeneous Structures in Controlling the Fault Slip Behavior in the Slow‐Earthquake Source Region Along the Nankai Subduction Zone, Southwest Japan
Author(s) -
Kurashimo Eiji,
Iwasaki Takaya,
Tsumura Noriko,
Iidaka Takashi
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl089882
Subject(s) - subduction , geology , seismology , episodic tremor and slip , induced seismicity , plate tectonics , slip (aerodynamics) , interplate earthquake , mantle (geology) , geophysics , tectonics , physics , thermodynamics
Abstract A seismic array observation across the slow‐earthquake source region in the eastern Kii Peninsula, southwest Japan, reveal the detailed structure and seismicity along the upper boundary of the subducted Philippine Sea Plate. Tomography analysis and earthquake reflection imaging clarify the geometry of the upper boundary of the Philippine Sea Plate with a subduction angle of ∼15° at a depth range of 22–30 km. We observe intraslab low‐frequency earthquakes (LFEs) in and around the low‐Vp and high‐Vp/Vs zones, which are located above the intraslab earthquakes that are controlled by the dehydration embrittlement of serpentine. The intraslab LFE activity may be related to fluid movement. Fluids, which are derived from both dehydration of the serpentinized oceanic mantle and crustal eclogitization, may control the fault slip behavior. Therefore, the fluid behavior around the subducting plate boundary has an important role in controlling the downdip limit of the seismogenic zone.