scholarly journals Migration of Deep Low‐Frequency Tremor Triggered by Teleseismic Earthquakes in the Southwest Japan Subduction Zone

2018 ◽  
Vol 45 (8) ◽  
pp. 3413-3419 ◽  
Author(s):  
Ryo Kurihara ◽  
Kazushige Obara ◽  
Akiko Takeo ◽  
Takuto Maeda
Keyword(s):  
Subduction Zone ◽  
Low Frequency ◽  
Southwest Japan ◽  
Japan Subduction Zone

scholarly journals Episodic slow slip events accompanied by non-volcanic tremors in southwest Japan subduction zone

2004 ◽  
Vol 31 (23) ◽  
Author(s):  
Kazushige Obara ◽  
Hitoshi Hirose ◽  
Fumio Yamamizu ◽  
Keiji Kasahara
Keyword(s):  
Subduction Zone ◽  
Slow Slip ◽  
Southwest Japan ◽  
Slow Slip Events ◽  
Japan Subduction Zone

Updated attenuation tomography of Japan subduction zone

2019 ◽  
Vol 219 (3) ◽  
pp. 1679-1697 ◽  
Author(s):  
Zewei Wang ◽  
Dapeng Zhao
Keyword(s):  
Subduction Zone ◽  
Wave Attenuation ◽  
Water Saturation ◽  
Low Frequency ◽  
Model Errors ◽  
Bound Constraints ◽  
Unknown Parameters ◽  
Study Region ◽  
Japan Subduction Zone ◽  
Q Values

SUMMARY We determine an updated model of P- and S-wave attenuation (Qp, Qs) tomography of the Japan subduction zone using an improved inversion scheme, and derive the first Qp/Qs model of the study region. We establish a system of observation t* equations by taking 1/Q values at 3-D grid nodes arranged in the study volume as unknown parameters. This scheme can eliminate model errors caused by ignoring high-order terms of the Taylor expansion in the Q-format scheme adopted by previous studies. The inversion problem is considered as a quadratic programming problem with bound constraints for best fitting the observed t* data in a least-squares sense. The 3-D attenuation model is obtained by using a limited-memory Broyden–Fletcher–Goldfarb–Shanno algorithm for bound constrained optimization. Because this inversion scheme uses bound constraints to avoid negative Q values, damping regularization is not needed, hence the ranges of Qp and Qs values obtained are less affected by human subjectivity. The subducting Pacific and Philippine Sea slabs exhibit high-Q and high Qp/Qs, whereas the mantle wedge beneath the volcanic front and back-arc area shows low-Q and low Qp/Qs. Both Qp and Qs vary in a range of 10–2000, and the Qp/Qs ratio changes from 0.4 to 1.4. Our results reveal a narrow high-Qp/Qs belt that is coincident with the distribution of volcanic and non-volcanic low-frequency micro-earthquakes (M 0.0–2.5), which may reflect high water-saturation anomalies that are probably associated with slab-derived fluids and responsible for the generation of low-frequency micro-earthquakes.

scholarly journals Total energy of deep low‐frequency tremor in the Nankai subduction zone, southwest Japan

2016 ◽  
Vol 43 (6) ◽  
pp. 2562-2567 ◽  
Author(s):  
Satoshi Annoura ◽  
Kazushige Obara ◽  
Takuto Maeda
Keyword(s):  
Total Energy ◽  
Subduction Zone ◽  
Low Frequency ◽  
Southwest Japan ◽  
Nankai Subduction Zone
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