Slab‐derived fluids, fore‐arc hydration, and sub‐arc magmatism beneath Kyushu, Japan

• Published in: Geophysical research letters 2015-03, Vol.42 (6), p.1685-1693
• Main Authors: Saita, Hiroto, Nakajima, Junichi, Shiina, Takahiro, Kimura, Jun‐Ichi
• Format: Article
• Language: English
• Subjects: Area; Attenuation; Depth; Fluid dynamics; Fluid flow; Fluids; Geophysics; Hydration; intermediate‐depth earthquakes; Lava; Magma; Mantle; Moho; Ocean circulation; P waves; Peridotite; Plate tectonics; Regions; seismic attenuation; serpentine; Tectonic processes; Three dimensional; Three dimensional flow; Upwelling; upwelling flow; Volcanic activity; Volcanoes; Wave attenuation
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL063084

We estimate the three‐dimensional (3‐D) P wave attenuation structure beneath Kyushu, Japan, using a large number of high‐quality waveform data. Our results show that the mantle wedge is characterized by high‐attenuation regions in the fore‐arc corner and in the back‐arc beneath volcanoes, with the two regions separated by a low‐attenuation area. The volcanic gap in central Kyushu is underlain by low attenuation below the Moho. High attenuation in the fore arc is probably associated with serpentinized peridotite, while that in the back arc is interpreted as an upwelling flow that is the source of arc magmas. The presence of low‐attenuation mantle that separates the high‐attenuation hydrated, fore‐arc, and back‐arc mantle regions suggests that fluids are supplied from two depth levels of the slab by different mechanisms. Low attenuation beneath the volcanic gap probably results from intricate 3‐D mantle flow that is caused by tectonic processes such as back‐arc extension and ridge collision. Key Points The first study on P wave attenuation structure beneath Kyushu Characteristic attenuation structures associated with slab‐derived fluids A volcanic gap controlled by the absence of a concentrated upwelling flow