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

scholarly journals Interseismic deformation of the Nankai subduction zone, southwest Japan, inferred from three-dimensional crustal velocity fields

2007 ◽  
Vol 59 (10) ◽  
pp. 1073-1082 ◽  
Author(s):  
Takao Tabei ◽  
Mari Adachi ◽  
Shin’ichi Miyazaki ◽  
Tsuyoshi Watanabe ◽  
Sayomasa Kato
Keyword(s):  
Subduction Zone ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Southwest Japan ◽  
Crustal Velocity ◽  
Interseismic Deformation ◽  
Nankai Subduction Zone

scholarly journals Detection of deep low-frequency earthquakes in the Nankai subduction zone over 11 years using a matched filter technique

2020 ◽  
Author(s):  
Aitaro Kato ◽  
Shigeki Nakagawa
Keyword(s):  
Subduction Zone ◽  
Matched Filter ◽  
Low Frequency ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Filter Technique ◽  
Episodic Tremor And Slip ◽  
Nankai Subduction Zone ◽  
Spatio Temporal

Abstract To improve our understanding of the long-term behavior of low-frequency earthquakes (LFEs) along the tremor belt of the Nankai subduction zone, we applied a matched filter technique to continuous seismic data recorded by a dense and highly sensitive seismic network over an 11 year window, April 2004 to August 2015. We detected a total of ~510,000 LFEs, or ~23× the number of LFEs in the JMA catalog for the same period. During long-term slow slip events (SSEs) in the Bungo Channel, a series of migrating LFE bursts intermittently occurred along the fault-strike direction, with slow hypocenter propagation. Elastic energy released by long-term SSEs appears to control the extent of LFE activity. We identify slowly migrating fronts of LFEs during major episodic tremor and slip (ETS) events, which extend over distances of up to 100 km and follow diffusion-like patterns of spatial evolution with a diffusion coefficient of ~10 4 m 2 /s. This migration pattern closely matches the spatio-temporal evolution of tectonic tremors reported by previous studies. At shorter distances, up to 15 km, we discovered rapid diffusion-like migration of LFEs with a coefficient of ~10 5 m 2 /s. We also recognize that rapid migration of LFEs occurred intermittently in many streaks during major ETS episodes. These observations suggest that slow slip transients contain a multitude of smaller, temporally clustered fault slip events whose evolution is controlled by a diffusional process.

Spatial relationship between shallow very low frequency earthquakes and the subducted Kyushu-Palau Ridge in the Hyuga-nada region of the Nankai subduction zone

2020 ◽  
Vol 222 (3) ◽  
pp. 1542-1554
Author(s):  
Takashi Tonegawa ◽  
Yusuke Yamashita ◽  
Tsutomu Takahashi ◽  
Masanao Shinohara ◽  
Yasushi Ishihara ◽  
...  
Keyword(s):  
Rayleigh Wave ◽  
Subduction Zone ◽  
Group Velocity ◽  
Low Frequency ◽  
Horizontal Distance ◽  
Structural Factors ◽  
Very Low Frequency ◽  
Slow Earthquakes ◽  
Seismic Records ◽  
Nankai Subduction Zone

SUMMARY Shallow very low frequency earthquakes (sVLFEs) have occurred recurrently at the shallow plate interface of the Hyuga-nada region of the western Nankai subduction zone, Japan. Although the locations of sVLFE epicentres have been determined using land-based seismic records with moderate accuracy, it is necessary to determine their locations more precisely to explore the relationship between sVLFEs and other shallow slow earthquakes and examine the structural factors that may control sVLFE activity. Here, we identified sVLFE epicentres using seismic records obtained from temporarily deployed ocean bottom seismometers (OBSs) in the Hyuga-nada region. Seismic observations involved the deployment of 5–13 OBSs for approximately 1 yr, with deployments conducted three times during 2014–2016 each time with changing OBS numbers and array distribution. As a result, one sVLFE episode, containing successive Rayleigh wave pulses with slow velocities due to marine sediments, could be detected at a frequency band of 0.1–0.15 Hz per observation, resulting in a total of three episodes. Rayleigh wave amplitudes of ordinary earthquakes in the continuous records were suppressed using earthquake catalogues. We estimated the dispersion curve for the Rayleigh wave group velocity for each array, which represented the averaged group velocity within the array, using coda interferometry, and applied an envelope correlation method (ECM) using the group velocities to continuous records. These processing provided sVLFE epicentres with horizontal distance errors of <5 km. Our results showed that sVLFEs depths, which were inferred from the contour line of the top of the Phillipine Sea Plate, had increased from <10 km to 10–15 km in the region of the subducted Kyusyu-Palau Ridge (KPR). It was also apparent that migration of sVLFE epicentres occurred in 2015 from a depth of 15 km to shallower depths along the northern margin of the subducted KPR. These results identified the subducted KPR as a structural factor controlling the excitation conditions of sVLFE activities.

scholarly journals Triggering of tremor and inferred slow slip by small earthquakes at the Nankai subduction zone in southwest Japan

2014 ◽  
Vol 41 (22) ◽  
pp. 8053-8060 ◽  
Author(s):  
Jiangang Han ◽  
John E. Vidale ◽  
Heidi Houston ◽  
Kevin Chao ◽  
Kazushige Obara
Keyword(s):  
Subduction Zone ◽  
Slow Slip ◽  
Southwest Japan ◽  
Nankai Subduction Zone
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