Amplitude Corrections for Regional Seismic Discriminants

Taylor, Steven R.; Velasco, A. A.; Hartse, Hans E.; Phillips, W. S.; Walter, William R.; Rodgers, A. J.

doi:10.1007/978-3-0348-8169-2_3

Cited by 49 publications

(33 citation statements)

References 23 publications

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“…The beginning of the Lg window is defined by the analyst pick, or when a pick is not available, the group velocity 3.45 km/s. The end of the window is defined by the group velocity 2.8 km/s, and the minimum window length is 1 s. These windows are used to measure time-domain root-mean-squares amplitudes, which are converted to pseudo-spectral amplitudes in the passband of 1-2 Hz via the method of TAYLOR et al (2002). Amplitudes are kept if the pre-event signal-to-noise ratio (SNR) exceeds two.…”

Section: Data Set and Attenuation Tomography Techniquesmentioning

confidence: 99%

“…Local and regional distance attenuation of seismic phases is important in earthquake hazard prediction. Quantifying seismic wave attenuation and correcting for its effects improves source parameter studies, which will aid in discrimination of small nuclear tests from naturally occurring earthquakes (e.g., BAKER et al, 2004;MAYEDA et al, 2003;TAYLOR et al, 2002). Current event identification relies on Q models to remove propagation effects, revealing source differences.…”

Section: Introductionmentioning

confidence: 99%

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Attenuation Tomography of the Yellow Sea/Korean Peninsula from Coda-source normalized and direct Lg Amplitudes

Ford

Phillips

Walter

et al. 2009

Pure Appl. Geophys.

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Abstract-We invert for regional attenuation of the crustal phase Lg in the Yellow Sea/Korean Peninsula (YSKP) using three different amplitude attenuation tomography methods. The first method solves for source, site, and path attenuation. The second method uses a scaling relationship to set the initial source amplitude and interpret the source term after inversion. The third method implements a coda-derived source spectral correction. By comparing methods with slightly different assumptions we are able to make a more realistic assessment of the uncertainties in the resulting attenuation maps than is obtainable through formal error analysis alone. We compare the site, source and path-terms produced by each method and comment on attenuation, which correlates well with tectonic and topographic features in the region. Source terms correlate well with each other and with magnitude. Site terms are similar except for two stations that are located in a region that has the greatest difference in path term, which demonstrates the site/path trade-off. Another region of path term difference has the fewest crossing paths, where the tomography method employing the coda-derived spectral correction may perform more accurately since it is not as susceptible to the source/ path trade-off. The Bohai Bay basin, an area of extension, is a region of high attenuation, and regions of low attenuation occur along topographic highs located in the Da-xin-an-ling and Changbai Mountains and Mount Taishan.

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Section: Data Set and Attenuation Tomography Techniquesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Attenuation Tomography of the Yellow Sea/Korean Peninsula from Coda-source normalized and direct Lg Amplitudes

Ford

Phillips

Walter

et al. 2009

Pure Appl. Geophys.

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“…In spite of these conclusions, seismologists commonly use a frequency-independent power-law model to approximate P n geometric spreading in the real Earth when analyzing observed data (e.g., Sereno et al, 1988;Zhu et al, 1991;Taylor et al, 2002). Occasionally, researchers combine P n geometric spreading and attenuation into a single distance-decay term in order to avoid the difficulty of isolating P n geometric-spreading effects (e.g., Chun et al, 1989;Tinker and Wallace, 1997).…”

Section: Introductionmentioning

confidence: 99%

“…Occasionally, researchers combine P n geometric spreading and attenuation into a single distance-decay term in order to avoid the difficulty of isolating P n geometric-spreading effects (e.g., Chun et al, 1989;Tinker and Wallace, 1997). Because of the apparent incompatibility between the behavior of P n in the real Earth and its power-law geometric-spreading representation, Taylor et al (2002) postulated that the use of a frequency-independent power-law spreading model might be the reason for difficulties encountered in fitting the P n spectra in their study. The common practice of representing P n geometric spreading in the real Earth with a frequency-independent power-law model may simply be a choice of convenience due to the unavailability of a more accurate, easy-to-use, frequency-dependent P n geometric-spreading model, even for a simple reference velocity structure.…”

Section: Introductionmentioning

confidence: 99%

Geometric Spreading of Pn and Sn in a Spherical Earth Model

Yang¹,

Lay²,

Xie³

et al. 2007

Bulletin of the Seismological Society of America

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Geometric spreading of P n and S n waves in a spherical Earth model is different than that of classical headwaves and is frequency dependent. The behavior cannot be fully represented by a frequency-independent power-law model, as is commonly assumed. The lack of an accurate representation of P n and S n geometric spreading in a spherical Earth model impedes our ability to characterize Earth properties including anelasticity. We conduct numerical simulations to quantify P n and S n geometric spreading in a spherical Earth model with constant mantle-lid velocities. Based on our simulation results, we present new empirical P n and S n geometricspreading models in the form Gr; f 10 n 3 f =r 0 r 0 =r n 1 f logr 0 =rn 2 f and n i f n i1 logf=f 0 2 n i2 logf=f 0 n i3 , where i 1, 2, or 3; r is epicentral distance; f is frequency; r 0 1 km; and f 0 1 Hz. We derive values of coefficients n ij by fitting the model to computed P n and S n amplitudes for a spherical Earth model having a 40-km-thick crust, generic values of P and S velocities, and a constant-velocity uppermost mantle. We apply the new spreading model to observed data in Eurasia to estimate average P n attenuation, obtaining more reasonable results compared to using a standard power-law model. Our new P n and S n geometric-spreading models provide generally applicable reference behavior for spherical Earth models with constant uppermost-mantle velocities.

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“…Walter et al, 1995;Taylor, 1996;Hartse et al, 1997;Kim et al, 1997;Rodgers and Walter, 2002;Taylor et al, 2002;Bottone et al, 2002;Walter et al, 2007). The application of this discriminant to broad regions, however, has been hampered by large variations in the amplitudes of phases due to propagation effects in the crust and upper mantle.…”

Section: Introductionmentioning

confidence: 99%

Testing Event Discrimination over Broad Regions using the Historical Borovoye Observatory Explosion Dataset

Pasyanos

Ford

Walter

2012

Pure Appl. Geophys.

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We test the performance of high-frequency regional P/S discriminants to differentiate between earthquakes and explosions at test sites and over broad regions using a historical dataset of explosions recorded at the Borovoye observatory in Kazakhstan. We compare these explosions to modern recordings of earthquakes at the same location. We then evaluate the separation of the two types of events using the raw measurements and those where the amplitudes are corrected for 1-D and 2-D attenuation structure. We find that high-frequency P/S amplitudes can reliably identify earthquakes and explosions and that the discriminant is applicable over broad regions as long as propagation effects are properly accounted for. Lateral attenuation corrections provide the largest improvement in the 2-4 Hz band, the use of which may allow us to examine smaller, distant events that have lower signal-to-noise at higher frequencies. We also find variations in P/S ratios among the three main nuclear testing locations within the Semipalatinsk Test Site which, due to their nearly identical paths to BRVK, must be a function of differing geology and emplacement conditions.

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Amplitude Corrections for Regional Seismic Discriminants

Cited by 49 publications

References 23 publications

Attenuation Tomography of the Yellow Sea/Korean Peninsula from Coda-source normalized and direct Lg Amplitudes

Attenuation Tomography of the Yellow Sea/Korean Peninsula from Coda-source normalized and direct Lg Amplitudes

Geometric Spreading of Pn and Sn in a Spherical Earth Model

Testing Event Discrimination over Broad Regions using the Historical Borovoye Observatory Explosion Dataset

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