scholarly journals Event couple spectral ratio Q method for earthquake clusters: application to North-West Bohemia

2018 ◽  
Author(s):  
Marius Kriegerowski ◽  
Simone Cesca ◽  
Matthias Ohrnberger ◽  
Torsten Dahm ◽  
Frank Krüger
Keyword(s):  
Wave Attenuation ◽  
Attenuation Factor ◽  
Source Region ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Earthquake Swarms ◽  
North West ◽  
High Attenuation ◽  
West Bohemia ◽  
Spectral Ratio Method

Abstract. We develop an amplitude spectral ratio method for event couples from clustered earthquakes to estimate seismic wave attenuation (Q−1) in the source volume. The method allows to study attenuation within the source region of earthquake swarms or aftershocks at depth, independent of wave path and attenuation between source region and surface station. We exploit the high frequency slope of phase spectra using multitaper spectral estimates. The method is tested using simulated full wavefield seismograms affected by recorded noise and finite source rupture. The synthetic tests verify the approach and show that solutions are independent of focal mechanisms, but also show that seismic noise may broaden the scatter of results. We apply the event couple spectral ratio method to North-West Bohemia, Czech Republic, a region characterized by the persistent occurrence of earthquake swarms in a confined source region at mid-crustal depth. Our method indicates a strong anomaly of high attenuation in the source region of the swarm with an averaged attenuation factor of Qp 

scholarly journals Event couple spectral ratio <i>Q</i> method for earthquake clusters: application to northwest Bohemia

Solid Earth ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 317-328
Author(s):  
Marius Kriegerowski ◽  
Simone Cesca ◽  
Matthias Ohrnberger ◽  
Torsten Dahm ◽  
Frank Krüger
Keyword(s):  
Wave Attenuation ◽  
Attenuation Factor ◽  
Source Region ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Earthquake Swarms ◽  
High Attenuation ◽  
Spectral Estimates ◽  
Wave Path ◽  
Spectral Ratio Method

Abstract. We develop an amplitude spectral ratio method for event couples from clustered earthquakes to estimate seismic wave attenuation (Q−1) in the source volume. The method allows to study attenuation within the source region of earthquake swarms or aftershocks at depth, independent of wave path and attenuation between source region and surface station. We exploit the high-frequency slope of phase spectra using multitaper spectral estimates. The method is tested using simulated full wave-field seismograms affected by recorded noise and finite source rupture. The synthetic tests verify the approach and show that solutions are independent of focal mechanisms but also show that seismic noise may broaden the scatter of results. We apply the event couple spectral ratio method to northwest Bohemia, Czech Republic, a region characterized by the persistent occurrence of earthquake swarms in a confined source region at mid-crustal depth. Our method indicates a strong anomaly of high attenuation in the source region of the swarm with an averaged attenuation factor of Qp<100. The application to S phases fails due to scattered P-phase energy interfering with S phases. The Qp anomaly supports the common hypothesis of highly fractured and fluid saturated rocks in the source region of the swarms in northwest Bohemia. However, high temperatures in a small volume around the swarms cannot be excluded to explain our observations.

Calculation of Qβ using the spectral ratio method in Northern Baja California, Mexico

1984 ◽  
Vol 74 (1) ◽  
pp. 91-96
Author(s):  
C. J. Rebollar
Keyword(s):  
Travel Time ◽  
Baja California ◽  
Epicentral Distance ◽  
Attenuation Factor ◽  
Low Frequency ◽  
Spectral Ratio ◽  
Corner Frequency ◽  
Ratio Method ◽  
Frequency Level ◽  
Spectral Ratio Method

Abstract The spectral ratio method for measuring absorption in the Peninsular Ranges region of Northern Baja California has been used. A Qβ from 240 to 350 was calculated in the range of frequencies from 1 to 13 Hz independent of frequency. Simple theoretical spectra of the form E(f) = Ω[(f/fc)2 +1]−1*exp(−πftQ−1) where ω is the low-frequency level, fc is the corner frequency, t is the travel time, and Q is the attenuation factor, match the observed spectra at ENX and CBX stations. The epicentral distance at ENX is about 16 and 57 km at CBX.

Measuring the sediment thickness in urban areas using revised H/V spectral ratio method

2019 ◽  
Vol 260 ◽  
pp. 105223 ◽  
Author(s):  
Baoqing Tian ◽  
Yanan Du ◽  
Zhiwei You ◽  
Ruohan Zhang
Keyword(s):  
Urban Areas ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Sediment Thickness ◽  
Spectral Ratio Method

Damping-ratio measurements by the spectral-ratio method

2006 ◽  
Vol 43 (11) ◽  
pp. 1180-1194 ◽  
Author(s):  
Yu-Hsing Wang ◽  
Wai Man Yan ◽  
Kai Fung Lo
Keyword(s):  
Damping Ratio ◽  
Near Field ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Bender Elements ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus ◽  
Spectral Ratio Method ◽  
Near Field Effect

In this paper, bender elements are used as sensors to measure the damping ratio of soil by the spectral-ratio method. The results of numerical and physical experiments suggest that adequate measurement precision can be achieved by reducing the two types of inherent biases arising from (i) the near-field effect and (ii) the different transfer functions of the two receiver bender elements. The first bias can be avoided by setting sensors to r1/λ ≥ 2.0 and r1/r2 ≥ 2.0, where r1 and r2 are the distances between the source and the first and second receivers, respectively; and λ is the wavelength. The second bias can be minimized by modifying the original spectral-ratio method to accommodate the self-healing technique. The damping ratios, measured by this modified method, obtained from the experiment conducted in a tailor-made, true-triaxial apparatus are very similar to those obtained from resonant column tests under the same state of stress.Key words: bender element, damping ratio, spectral-ratio method, near-field effect, true-triaxial apparatus.

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