scholarly journals Attenuation Characteristics of S-waves in a Sedimentary Layer-basement System in the Kanto Region, Japan, for a Frequency Range of 0.5 to 16Hz

2002 ◽  
Vol 55 (1) ◽  
pp. 19-31 ◽  
Author(s):  
Shigeo KINOSHITA ◽  
Miho OHIKE
Keyword(s):  
Frequency Range ◽  
S Waves ◽  
Kanto Region ◽  
Attenuation Characteristics ◽  
Sedimentary Layer

Converted shear waves as seen by ocean bottom seismometers and surface buoys

1977 ◽  
Vol 67 (5) ◽  
pp. 1291-1302 ◽  
Author(s):  
Brian T. R. Lewis ◽  
James McClain
Keyword(s):  
Shear Waves ◽  
Shear Velocity ◽  
Ocean Bottom ◽  
Sediment Layer ◽  
S Waves ◽  
High Attenuation ◽  
Ocean Bottom Seismometers ◽  
Sedimentary Layer ◽  
Low Shear

abstract It is found that ocean bottom seismometers (O.B.S.) deployed in sedimented areas produce markedly different seismograms from surface hydrophones. These differences are found to be due to ringing on the O.B.S. records produced by converted shear waves trapped in the sediment layer. These shear waves do not propagate into the water and hence the hydrophone record is much “cleaner” than the O.B.S. record. It is also shown that the presence of refracted shear waves like P-S-P and P-S-S may be related to the presence of a sedimentary layer in some areas. It is suggested that the disappearance of refracted S waves in some areas without sediment is related to high attenuation and/or very low shear velocities caused by cracks and inhomogeneities in the crust. Under sedimented areas the cracks may be sufficiently filled so as to substantially reduce the attenuation and/or increase the bulk shear velocity.

scholarly journals A review of nonparametric attenuation functions computed for different regions of Italy

1999 ◽  
Vol 42 (4) ◽  
Author(s):  
R. R. Castro ◽  
M. Mucciarelli ◽  
G. Monachesi ◽  
F. Pacor ◽  
R. Berardi
Keyword(s):  
Spectral Amplitude ◽  
Italian Region ◽  
Central Apennines ◽  
Hypocentral Distance ◽  
S Waves ◽  
Marche Region ◽  
Fair Comparison ◽  
Rate Of Decay ◽  
Strong Amplitude ◽  
Attenuation Characteristics

We used a set of previously published nonparametric attenuation functions to calculate average functions for the Italian region. These nonparametric functions describe the spectral amplitude decay of the S waves as a function of distance for 14 frequencies between 1 and 20 Hz for the regions of Lombardia-Piemonte, Eastern Sicily, Friuli, Marche and the Central Apennines. Since all the attenuation functions were obtained using the same methodology, we were able to make a fair comparison of the attenuation characteristics of the different regions. In general, while the Central Apennines show the strongest amplitude decay for all the frequencies analyzed, the regions of Lombardia and Eastern Sicily show the smallest attenuation. The Marche region also shows a strong amplitude decay, particularly for frequencies f > 3 Hz, and in the frequency band between 1 and 3 Hz the rate of decay of the spectral amplitudes with distance becomes similar to that of the region of Friuli. Since the attenuation functions analyzed represent different geologic and tectonic environments, we used them to calculate an average set of attenuation functions, one per frequency, for the hypocentral distance range between 10 and 120 km. The resulting functions permit a mean attenuation correction to spectral records of S waves in regions of Italy where the specific values of the attenuation parameters are unknown.

scholarly journals Upstream Ultra-Low Frequency Waves Observed by MESSENGER's Magnetometer: Implications for Particle Acceleration at Mercury's Bow Shock

2020 ◽  
Author(s):  
Norberto Romanelli ◽  
Gina DiBraccio ◽  
Daniel Gershman ◽  
Guan Le ◽  
Christian Mazelle ◽  
...  
Keyword(s):  
Solar Wind ◽  
Wave Amplitude ◽  
Solar Wind Speed ◽  
Low Frequency ◽  
Space Environment ◽  
Occurrence Rate ◽  
Frequency Range ◽  
S Waves ◽  
Mercury Surface ◽  
Low Frequency Waves

<p>In this work we perform the first statistical analysis of the main properties of waves observed in the 0.05–0.41 Hz frequency range in the Hermean foreshock by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Magnetometer. Although we find similar polarization properties to the '30 s' waves observed at the Earth's foreshock, the normalized wave amplitude (∼0.2) and occurrence rate (∼0.5%) are much smaller. This suggests significant lower backstreaming proton fluxes, due to the relatively low solar wind Alfvenic Mach number around Mercury. These differences could also be related to the relatively smaller foreshock size and/or more variable solar wind conditions. Furthermore, we estimate that the speed of resonant backstreaming protons in the solar wind reference frame (likely source for these waves) ranges between 0.95 and 2.6 times the solar wind speed. The closeness between this range and what is observed at other planetary foreshocks suggests that similar acceleration processes are responsible for this energetic population and might be present in the shocks of exoplanets.</p>

Source characteristics of small to moderate earthquakes in the Kanto region, Japan: application of a new definition of the S-wave time window length

1996 ◽  
Vol 86 (5) ◽  
pp. 1284-1291
Author(s):  
Kazutoshi Watanabe ◽  
Haruo Sato ◽  
Shigeo Kinoshita ◽  
Masakazu Ohtake
Keyword(s):  
Wave Energy ◽  
Seismic Moment ◽  
Time Window ◽  
P Wave ◽  
Corner Frequency ◽  
Window Length ◽  
S Wave ◽  
S Waves ◽  
Source Characteristics ◽  
Kanto Region

Abstract The S wave from a local earthquake generally consists of several pulses, in contrast to a simple pulse of P wave. This results in a large uncertainty in the estimation of seismic moment and wave energy when the window length for S-wave analysis is not chosen properly. In this study, we propose a new method to define objectively an appropriate time window length of the S wave for estimation of source characteristics based on the S-wave to P-wave energy ratio for a point shear dislocation source. Analyzing waveform data of 97 local earthquakes in the Kanto region, Japan, whose magnitudes M range from 3.3 to 6.0, we obtained simple equations for predicting the time window length of the S-wave TS as a function of earthquake magnitude or pulse width of P-wave TP; we got TS ≈ 1.8 TP for the relation between TP and TS. Applying the S-wave window thus defined, we estimated seismic energy E, seismic moment M0, and corner frequency fc for both P and S waves. Regression analysis of those parameters revealed (1) our method to define TS is confirmed by the fact that the seismic moment determined from P and S waves are consistent; (2) in the range of 1014 < M0 < 1018 (N·m), M0 is almost proportional to f−3c both for P and S waves; (3) the value of E/M0 is 2.7 ∼ 4.0 × 10−5; and (4) breakdown of the scaling relation is seen at M ≦ 4.

Measurement of Q−1 for S waves in mudstone at Chikura, Japan: Comparison of incident and reflected phases in borehole seismograms

1992 ◽  
Vol 82 (1) ◽  
pp. 148-163
Author(s):  
Yoshimitsu Fukushima ◽  
Shigeo Kinoshita ◽  
Haruo Sato
Keyword(s):  
Principal Axis ◽  
Three Dimensional ◽  
Ground Surface ◽  
Head Wave ◽  
S Wave ◽  
Sh Waves ◽  
S Waves ◽  
Confidence Levels ◽  
Kanto Region ◽  
Ray Path

Abstract Seismograms from small events in the southern Kanto region have been recorded by a seismometer installed in a 732-m-deep borehole at Chikura observatory, Japan, where mudstone of early Pliocene age is found from the ground surface to the bottom of the borehole. Strong phases occurring 1.5 ∼ 1.6 sec after the S-wave arrival were interpreted as reflections at the ground surface. Ray path directions of the incident S waves were determined from the minimum principal axis of the three-dimensional trajectory ellipsoid, which represents the particle motion for a head wave of S phase. Transverse horizontal SH components were used to estimate the Q−1 value for S waves. Assuming the free surface acted as an 100% reflector for the SH waves and the incident SH phase as an input and the reflected phase as an output, we calculated system functions. The Q−1 value was measured from the transfer characteristics between the incident and the reflected phases in a single seismogram, thus no corrections were necessary for source or site (including instrument) effects. If we applied a power law model, the following relationship was obtained from the regression analyses of 20 events: log 10 ( Q − 1 ) = ( − 0.52 ± 0.48 ) ⋅ log 10 ( f ) − ( 1.28 ± 0.22 ) ( 1.0 < f < 5.0 Hz ) , where f is frequency in Hz and error values are the 95% confidence levels of the regression coefficients.

scholarly journals SU8 ridge-gap waveguide resonator

2014 ◽  
Vol 6 (5) ◽  
pp. 459-465 ◽  
Author(s):  
Sofia Rahiminejad ◽  
Elena Pucci ◽  
Sjoerd Haasl ◽  
Peter Enoksson
Keyword(s):  
Cost Effective ◽  
Q Factor ◽  
Frequency Range ◽  
Waveguide Resonator ◽  
New Process ◽  
Cost Effective Alternative ◽  
Attenuation Loss ◽  
Work Done ◽  
Attenuation Characteristics ◽  
Made In

In this paper, we present the first ridge-gap waveguide resonator made with a polymer base. It is designed for the frequency range 220–325 GHz, and is fabricated solely using a Au coated two-layer SU8-based process. The design is based on previous work done with Si. The new process has advantages such as fewer and cheaper process steps. The SU8 ridge-gap waveguide resonator is made in order to obtain attenuation characteristics via the measured Q-factor of the resonator. The ridge-gap waveguide resonator has the same dimensions as the previous one fabricated in Si, and the same thickness of the Au coating. The SU8-based resonator shows an attenuation loss of 0.41 dB/mm at 282.2 GHz compared to the Si-based resonator with an attenuation loss of 0.043 dB/mm at 283.5 GHz. This makes the SU8 process a more cost-effective alternative to the Si process

Broadband Wave Attenuation in Locally Resonant Periodic Flexural Beams With Force-Moment Resonators

2013 ◽  
Author(s):  
Michael Y. Wang ◽  
Xiaoming Wang
Keyword(s):  
Degrees Of Freedom ◽  
Wave Attenuation ◽  
Low Frequency ◽  
Flexural Wave ◽  
Frequency Range ◽  
Resonant Structures ◽  
Force Moment ◽  
Flexural Wave Propagation ◽  
Bloch’S Theorem ◽  
Attenuation Characteristics

We investigate flexural wave propagation in Euler-Bernoulli beams with periodically suspended 2-DOF force-moment resonators. We use the transfer matrix method for a unit cell in the beam in conjunction with Bloch’s theorem, to define the dispersion curves and frequency band structure. Our analysis shows that the uncoupled force-moment resonators generate rich attenuation properties that are not observed in the conventional locally resonant structures with suspended force-only (or moment-only) vibrators. As a prime focus, we identify a Bragg-like band gap below the resonance frequency of the resonator and its coupling with the resonance gap, giving rise to a potentially super-wide attenuation gap that can be tuned for any low frequency range. The analysis presented can be extended to other types of phononic meta-materials and structures of multi-degrees of freedom (and distributed) resonators, which may exhibit more practically significant wave attenuation characteristics.

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