Characteristics of slow earthquakes in the very low frequency band: Application to the Cascadia subduction zone

2016 ◽  
Vol 121 (8) ◽  
pp. 5942-5952 ◽  
Author(s):  
Satoshi Ide
Keyword(s):  
Subduction Zone ◽  
Frequency Band ◽  
Low Frequency ◽  
Cascadia Subduction Zone ◽  
Very Low Frequency ◽  
Slow Earthquakes

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 Very low frequency earthquakes along the Ryukyu subduction zone

2012 ◽  
Vol 39 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Masataka Ando ◽  
Yoko Tu ◽  
Hiroyuki Kumagai ◽  
Yoshiko Yamanaka ◽  
Cheng-Horng Lin
Keyword(s):  
Subduction Zone ◽  
Low Frequency ◽  
Very Low Frequency

Heart rate variability and dissociation in panic disorder

2011 ◽  
Vol 26 (S2) ◽  
pp. 147-147
Author(s):  
T. Diveky ◽  
D. Kamaradova ◽  
A. Grambal ◽  
K. Latalova ◽  
J. Prasko ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Panic Disorder ◽  
Frequency Band ◽  
High Frequency ◽  
Power Spectra ◽  
Low Frequency ◽  
Very Low Frequency ◽  
Significant Difference ◽  
Before And After

The aim of our study is to measure very low frequency band (VLF), low frequency band (LF) and high frequency band (HF) components of R-R interval during orthostatic experiment in panic disorder patients before and after treatment.MethodsWe assessed heart rate variability in 19 patients with panic disorder before and after 6-weeks treatment with antidepressants combined with CBT and 18 healthy controls. They were regularly assessed on the CGI, BAI and BDI. Heart rate variability was assessed during 5 min standing, 5 min supine and 5 min standing positions before and after the treatment. Power spectra were computed using a fast Fourier transformation for very low frequency - VLF (0.0033 - 0.04 Hz), low-frequency - LF (0.04-0.15 Hz) and high frequency - HF (0.15-0.40 Hz) powers.Results19 panic disorder patients entered a 6-week open-label treatment study with combination of SSRI and cognitive behavioral therapy. A combination of CBT and pharmacotherapy proved to be the effective treatment of patients. They significantly improved in all rating scales. There were highly statistical significant differences between panic patients and control group in all components of power spectral analysis in 2nd and in two component of 3rd (LF and HF in standing) positions. There was also statistically significant difference between these two groups in LF/HF ratio in supine position (2nd). During therapy there was tendency to increasing values in all three positions in components of HRV power spectra, but there was only statistically significant increasing in HF1 component.Supported by project IGA MZ ČR NS 10301-3/2009

scholarly journals SPECIAL PURPOSE PULSAR TELESCOPE FOR THE DETECTION OF COSMIC GRAVITATIONAL WAVES

2002 ◽  
Vol 11 (07) ◽  
pp. 1061-1065 ◽  
Author(s):  
Shou-Guan Wang ◽  
Zong-Hong Zhu ◽  
Zhen-Long Zou ◽  
Yuan-Zhong Zhang
Keyword(s):  
Gravitational Waves ◽  
Radio Telescope ◽  
Frequency Band ◽  
Low Frequency ◽  
Millisecond Pulsars ◽  
Very Low Frequency ◽  
Upper Limit ◽  
Stochastic Backgrounds

Pulsars can be used to search for stochastic backgrounds of gravitational waves of cosmological origin within the very low frequency band (VLF), 10-7 to 10-9 Hz. We propose to construct a special 50 m radio telescope. Regular timing measurements of about 10 strong millisecond pulsars will perhaps allow the detection of gravitational waves within VLF or at least will give a more stringent upper limit.

scholarly journals Coherence between oscillations in the cardiorespiratory system and tissue oxygen index in muscle recovering from intensive exercise in humans

2019 ◽  
Vol 106 (3) ◽  
pp. 261-271
Author(s):  
N Usuda ◽  
K Shirakawa ◽  
K Hatano ◽  
MO Abe ◽  
T Yunoki ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Phase Difference ◽  
Frequency Band ◽  
Oxygen Index ◽  
Arterial Oxygen Saturation ◽  
Low Frequency ◽  
Arterial Oxygen ◽  
Tissue Oxygen ◽  
Cardiorespiratory System ◽  
Very Low Frequency

It has been shown that the tissue oxygen index (TOI) measured by near-infrared spectroscopy oscillates at very low frequencies during recovery after exercise and that this oscillation is derived from interactions among biochemical substances involved in oxidative metabolism in skeletal muscle. As a further step, we examined whether TOI in muscle interacts through oscillation with factors related to oxygen in the cardiorespiratory system. For this examination, coherence and phase difference between the TOI in the vastus lateralis and heart rate (HR) and between TOI and arterial oxygen saturation (SpO2) were sequentially determined during recovery (2–60 min) after severe cycle exercise with a workload of 7.5% of body weight for 20 s. Significant coherence between TOI and HR was obtained in the very low-frequency band (approximate range: 0.002–0.03 Hz) and in the low-frequency band (approximate range: 0.06–0.12 Hz). The phase difference was negative in the low-frequency band and positive in the very low-frequency band. The coherence between TOI and SpO2 was significant in the very low-frequency band. The phase difference was negative. There were no sequential changes in these coherences and phase differences. The results suggest that TOI in skeletal muscle interrelates with factors related to the heart and lungs.

scholarly journals Shallow very-low-frequency earthquakes accompany slow slip events in the Nankai subduction zone

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Masaru Nakano ◽  
Takane Hori ◽  
Eiichiro Araki ◽  
Shuichi Kodaira ◽  
Satoshi Ide
Keyword(s):  
Subduction Zone ◽  
Low Frequency ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Very Low Frequency ◽  
Nankai Subduction Zone

Possible shallow slow slip events in Hyuga-nada, Nankai subduction zone, inferred from migration of very low frequency earthquakes

2015 ◽  
Vol 42 (2) ◽  
pp. 331-338 ◽  
Author(s):  
Youichi Asano ◽  
Kazushige Obara ◽  
Takanori Matsuzawa ◽  
Hitoshi Hirose ◽  
Yoshihiro Ito
Keyword(s):  
Subduction Zone ◽  
Low Frequency ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Very Low Frequency ◽  
Nankai Subduction Zone
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