Qp-Qs relations in the sedimentary basin of the upper Mississippi Embayment using converted phases

1994 ◽  
Vol 84 (6) ◽  
pp. 1861-1868
Author(s):  
Kou-Cheng Chen ◽  
Jer-Ming Chiu ◽  
Yung-Tun Yang
Keyword(s):  
Sedimentary Basin ◽  
Vertical Component ◽  
Spectral Ratio ◽  
Unconsolidated Sediments ◽  
Ratio Method ◽  
Seismic Zone ◽  
Frequency Content ◽  
S Wave ◽  
Mississippi Embayment ◽  
Upper Mississippi Embayment

Abstract Three-component digital seismograms recorded by the 40 PANDA (Portable Array for Numerical Data Acquisition) stations in the New Madrid seismic zone were analyzed to study seismic wave attenuation in the sedimentary basin using the spectral ratio method. A prominent S-to-P (Sp) converted phase was generated at the boundary between the uppermost sedimentary basin and the underlying Paleozoic rocks. The direct S wave on the horizontal component is characterized by a lower-frequency content than that of the converted Sp wave on the vertical component. The differences in frequency content between the direct S and the Sp converted waves can be attributed to the different attenuation effects between P and S waves in the unconsolidated sediments. The spectral ratio between the low-frequency S wave and the high-frequency converted Sp wave from the bottom of the sediments can be used to yield a relationship between Qp and Qs in the sediments. Results from PANDA stations with well-constrained spectral ratios in the frequency range from 2 to 25 Hz give the Qp value ranging from 25 to 60 and Qs from 25 to 30 for the sedimentary basin in the upper Mississippi Embayment.

Shear-wave velocity of the sedimentary basin in the upper Mississippi embayment using S-to-P converted waves

1996 ◽  
Vol 86 (3) ◽  
pp. 848-856
Author(s):  
Kou-Cheng Chen ◽  
Jer-Ming Chiu ◽  
Yung-Tun Yang
Keyword(s):  
Travel Time ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Sedimentary Basin ◽  
Vertical Component ◽  
Seismic Zone ◽  
Mississippi Embayment ◽  
Upper Mississippi Embayment ◽  
Converted Waves

Abstract From mid-October 1989 to August 1992, 40 three-component PANDA (Portable Array for Numerical Data Acquisition) stations were deployed in the central New Madrid seismic zone. Three-component digital seismograms recorded by the PANDA stations in the region are characterized by (1) the very weak direct S arrivals on the vertical component, which can be identified unambiguously from the two horizontal components, and (2) at least two prominent secondary arrivals between the direct P and S arrivals, one (Sp) dominant on the vertical component and another (Ps) with smaller amplitude on the two horizontal components. Travel-time differences between the Sp and S and between the P and Ps are the same for different earthquakes recorded at the same station but are different at different stations even for the same event. Polarization analyses of three-component seismograms and travel-time measurements confirm the interpretation that these two secondary arrivals are the P-to-S (Ps) and S-to-P (Sp) converted waves that occur at the bottom of the sedimentary basin beneath each station. Since abundant well-log data are available in the upper Mississippi embayment, the thickness of the sediments beneath each seismic station can be estimated. Travel-time differences between the direct and the converted waves can be used to calculate average shear-wave velocity for the sediments beneath each station. The estimated shear-wave velocities of the sediments beneath PANDA stations vary from 0.45 to 0.67 km/sec. The higher shear-wave velocity associated with thicker sediments can be interpreted as a consequence of increasing compaction of unconsolidated sediments due to increasing overburden.

scholarly journals Site Response of the NARS-Baja and RESBAN Broadband Networks of the Gulf of California, México

2016 ◽  
Vol 55 (2) ◽  
Author(s):  
Lenin Ávila-Barrientos ◽  
Raúl R. Castro
Keyword(s):  
Ground Motion ◽  
Gulf Of California ◽  
Site Response ◽  
Vertical Component ◽  
Spectral Ratio ◽  
Ratio Method ◽  
S Wave ◽  
Amplification Factors ◽  
The Individual ◽  
Back Azimuth

We studied the seismic response of broadband stations located around the Gulf of California, Mexico, using the horizontal to vertical component spectral ratio method (HVSR). We analyzed 92 earthquakes recor-ded by the NARS-Baja and RESBAN networks, operated by CICESE. The database consists of events recorded between 2002 and 2006, with magnitudes ranging from 3.2 to 6.6. We rotated the records to find radial and transversal ground-motion components and we calculated Fourier spectra of S-wave windows recorded for the three ground-motion components. Then, we calculated HVSR for the individual components and the average of both horizontal components for every event. We analyze records from 20 stations located on sites with different geologic characteristics and we find azimuthal dependence on six of them that have amplification factors varying from 1.5 to up to 13 times at narrow back-azimuth ranges. We also find that sites with significant amplification factors (above three) show increasing amplification with increasing source magnitude.

scholarly journals PENGOLAHAN DATA MIKROTREMOR BERDASARKAN METODE HVSR DENGAN MENGGUNAKAN MATLAB

2020 ◽  
Vol 5 (1) ◽  
pp. 45-59
Author(s):  
Winda Styani Yuliawati ◽  
Syamsurijal Rasimeng ◽  
Karyanto Karyanto
Keyword(s):  
Data Processing ◽  
Vertical Component ◽  
Spectral Ratio ◽  
Dominant Frequency ◽  
Ratio Method ◽  
Type I ◽  
Site Class ◽  
Matlab Software ◽  
Hvsr Method ◽  
Earthquake Vulnerability

The research has conducted to get the result of Matlab program for microtremor data processing. The purpose of this research is to apply Matlab software into microtremor data processing. The microtremor is the ground motion to identify earthquake vulnerability by using HVSR (Horizontal to Vertical Spectral Ratio) method. The HVSR method for comparing both of horizontal component and vertical component on microtremor wave to obtain the result dominant frequency(f0) based on the high spectrum H/V value from the analysis of HVSR curve. Based on this research which concludes that microtremor data processing has processed using Matlab software. The result of this data processing gives similar value from the geopsy software. The value of dominant frequency by Matlab software and geopsy software calculation are classified on the site class type II which is dominantly alluvium. Whereas, the result of dominant period by geopsy and Matlab are classified on the site class type I which shows as the bedrock.

Overview of Research in The New Madrid Seismic Zone

1992 ◽  
Vol 63 (3) ◽  
pp. 193-208 ◽  
Author(s):  
Arch C. Johnston ◽  
Kaye M. Shedlock
Keyword(s):  
Field Investigation ◽  
Detailed Knowledge ◽  
New Madrid Seismic Zone ◽  
Research Front ◽  
Seismic Zone ◽  
Mississippi Embayment ◽  
Upper Mississippi Embayment ◽  
New Information ◽  
Seismogenic Faults ◽  
New Madrid

Abstract We review the development of understanding of the seismicity and tectonic structure of the New Madrid seismic zone and the upper Mississippi embayment. The broad framework of a failed intracontinental rift with reactivated seismogenic faults was not established until the mid-1970s. By the early 1990s a much more detailed knowledge of the rift and the current seismicity has been gained but fundamental questions remain. The 25 papers of this Special Issue of Seismological Research Letters convey the location of the most recent research front in such diverse fields as seismology, paleoseismology, seismic and potential-field investigation of rift structure, neotectonic deformation, and seismic hazard estimation and response. The new information content of these papers, considered ensemble, is enormous and highlights the tremendous progress made since the 1970s. These current studies, in turn, sharpen the focus on remaining outstanding problems of seismogenesis in the New Madrid seismic zone. We close with a discussion of what we believe will be the important foci of research in the 1990s.

Estimation of shear-wave interval attenuation from mode-converted data

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. D11-D19 ◽  
Author(s):  
Bharath Shekar ◽  
Ilya Tsvankin
Keyword(s):  
Shear Wave ◽  
Attenuation Coefficient ◽  
Reservoir Characterization ◽  
Wave Attenuation ◽  
Pure Shear ◽  
Synthetic Data ◽  
Spectral Ratio ◽  
Ratio Method ◽  
S Wave ◽  
Target Layer

Interval attenuation measurements provide valuable information for reservoir characterization and lithology discrimination. We extend the attenuation layer-stripping method of Behura and Tsvankin to mode-converted (PS) waves with the goal of estimating the S-wave interval attenuation coefficient. By identifying PP and PS events with shared ray segments and applying the [Formula: see text] method, we first perform kinematic construction of pure shear (SS) events in the target layer and overburden. Then, the modified spectral-ratio method is used to compute the effective shear-wave attenuation coefficient for the target reflection. Finally, application of the dynamic version of velocity-independent layer stripping to the constructed SS reflections yields the interval S-wave attenuation coefficient in the target layer. The attenuation coefficient estimated for a range of source-receiver offsets can be inverted for the interval attenuation parameters. The method is tested on multicomponent synthetic data generated with the anisotropic reflectivity method for layered VTI (transversely isotropic with a vertical symmetry axis) and orthorhombic media.

scholarly journals Discrimination of earthquakes and explosions in southern Russia using regional high-frequency three-component data from the IRIS/JSP Caucasus network

1997 ◽  
Vol 87 (3) ◽  
pp. 569-588 ◽  
Author(s):  
W.-Y. Kim ◽  
V. Aharonian ◽  
A. L. Lerner-Lam ◽  
P. G. Richards
Keyword(s):  
Free Surface ◽  
High Frequency ◽  
Vertical Component ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Spectral Ratios ◽  
Discrimination Power ◽  
Misclassification Probability ◽  
Southern Russia ◽  
Spectral Ratio Method

Abstract High-frequency regional records from small earthquakes (magnitude <4.5) and comparable magnitude chemical explosions are analyzed to find a reliable seismic discriminant in southern Russia near Kislovodsk. The digital, three-component seismograms recorded during 1992 by the Caucasus Network operated by Lamont-Doherty Earth Observatory since 1991 in the distance ranges 15 to 233 km are used. Mean vertical-component Pg/Lg spectral amplitude ratios in the band 8 to 18 Hz are about 1.3 and 3.2 for earthquakes and explosions, respectively, in this region. We find that the vertical-component Pg/Lg spectral ratio in the frequency band 8 to 18 Hz serves quite well for classifying these events. A linear discriminant function analysis indicates that the Pg/Lg spectral ratio method provides discrimination power with a total misclassification probability of about 7%. The Pg/Lg spectral ratios of rotated, three-component regional records improve the discrimination power of the spectral ratio method over the vertical-component Pg/Lg ratios. Preliminary analysis indicates that distance-corrected vertical-component Pg/Lg ratios improve the discrimination power by about 4% over uncorrected ratios. But we find that an even better discriminant is the Pg/Lg spectral ratio of the three-component regional records corrected for the free-surface effect. In the frequency band 8 to 18 Hz, the free-surface-corrected three-component Pg/Lg spectral ratio provides discrimination power with a total misclassification probability of only 2.6%. Free-surface-corrected and network-averaged Pg/Lg spectral ratios provide transportability of the spectral ratio method to various regions worldwide.

How frequency dependency of Q affects spectral ratio estimates

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. A39-A44 ◽  
Author(s):  
Boris Gurevich ◽  
Roman Pevzner
Keyword(s):  
Transmission Loss ◽  
Signal Amplitude ◽  
Spectral Ratio ◽  
Seismic Profile ◽  
Estimation Methods ◽  
Ratio Method ◽  
Frequency Content ◽  
Frequency Dependency ◽  
North West ◽  
True Value

Because seismic amplitudes can be affected by purely geometrical factors, attenuation is often estimated not from amplitudes but from the evolution of the amplitude spectra of the waveform. Such estimation methods (e.g., the spectral ratio method and the centroid frequency shift method) assume that the quality factor [Formula: see text] is constant (independent of frequency) in the frequency band of the signal. If this assumption is violated, then [Formula: see text] estimates become biased. In particular, when the frequency dependency of [Formula: see text] is a power law [Formula: see text], then [Formula: see text] is systematically under- or overestimated by a factor of [Formula: see text]. The errors are larger for larger values of [Formula: see text], particularly when [Formula: see text] is negative. In particular, if [Formula: see text], the frequency content of the signal does not change, and [Formula: see text] is estimated to be infinite, regardless of the true value of [Formula: see text]. To avoid these systematic errors, it is necessary to monitor the evolution of frequency content and amplitude with distance. Zero-offset vertical seismic profile data from the North West Shelf of Australia revealed the decay of the signal amplitude with depth that can be explained by a combination of intrinsic constant [Formula: see text] and a frequency-independent factor, which in turn is caused by the geometric spreading plus transmission loss due to variations of acoustic impedance on a scale larger than the dominant wavelength in the signal.

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