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Journal Article

The Development of Global Probabilistic Propagation Look‐Up Tables for Infrasound Celerity and Back‐Azimuth Deviation Available to Purchase

Emily A. Morton, Stephen J. Arrowsmith
Published: 01 October 2014
Seismological Research Letters (2014) 85 (6): 1223–1233.
DOI: https://doi.org/10.1785/0220140124
... and temporally ( Garcés et al. , 1998 ; Drob et al. , 2003 , 2010 ). Of particular importance for association and location is to have some constraints on the celerity (horizontal distance from source to receiver divided by travel time of sound wave) and the back‐azimuth deviation (bias in the recorded back...
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View PDF for article title, The Development of Global Probabilistic Propagation Look‐Up Tables for Infrasound Celerity and <span class="search-highlight">Back</span>‐<span class="search-highlight">Azimuth</span> <span class="search-highlight">Deviation</span>
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Journal Article

Comment on “ P -Wave Back-Azimuth and Slowness Anomalies Observed by an IMS Seismic Array LZDM” by Chunyue Hao and Zhong Zheng Available to Purchase

Lei Li
Published: 01 August 2011
Bulletin of the Seismological Society of America (2011) 101 (4): 1971–1975.
DOI: https://doi.org/10.1785/0120100256
...Lei Li Abstract At the LZDM seismic array, Hao and Zheng (2010) observed extremely large back-azimuth and slowness deviations for teleseismic P waves, the maximum values of which were 87.1° for back-azimuth deviation and 8.68 s/° for slowness deviation. Hao and Zheng argued that the majority...
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View PDF for article title, Comment on “ P -Wave <span class="search-highlight">Back</span>-<span class="search-highlight">Azimuth</span> and Slowness Anomalies Observed by an IMS Seismic Array LZDM” by Chunyue Hao and Zhong Zheng
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Add to Citation Manager for Comment on “ P -Wave <span class="search-highlight">Back</span>-<span class="search-highlight">Azimuth</span> and Slowness Anomalies Observed by an IMS Seismic Array LZDM” by Chunyue Hao and Zhong Zheng
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The effect of correcting for wind bias on infrasound location accuracy. (a) Predicted back‐azimuth deviation (colored dots) from ray tracing at predicted ground intercepts for a source at the true location. Posterior density functions over epicenter using (b) uncorrected infrasound back azimuths and (c) corrected infrasound back azimuths.

The effect of correcting for wind bias on infrasound location accuracy. (a)... Available to Purchase

Published: 30 December 2020
Figure 5. The effect of correcting for wind bias on infrasound location accuracy. (a) Predicted back‐azimuth deviation (colored dots) from ray tracing at predicted ground intercepts for a source at the true location. Posterior density functions over epicenter using (b) uncorrected infrasound back
Image
Number of detections in the early coda as a function of (left) event longitude or (right) latitude and relative back azimuth (deviation in degree from the theoretical event back azimuth [BAZ]) for each of the five arrays. The early coda is defined as the time window between the theoretical Lg arrival (corresponding to a group velocity of 3.5 km/s) and the time limit (tlim, red vertical line in Fig. 5). The black squares correspond to the relative final asymptotic back azimuth (AZf–BAZ). Different deviation behaviors for the arrays KKAR, MKAR, ABKAR, and BVAR between the eastern earthquakes and western earthquakes are observed. The vertical dashed line marks the longitude limit delimiting two groups of events: the western and eastern groups.

Number of detections in the early coda as a function of (left) event longit... Available to Purchase

Published: 24 January 2017
Figure 6. Number of detections in the early coda as a function of (left) event longitude or (right) latitude and relative back azimuth (deviation in degree from the theoretical event back azimuth [BAZ]) for each of the five arrays. The early coda is defined as the time window between
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Array beam and slowness plots of PKKKP and P′•d•P′ waves for event J. The lower slowness plots were made for time periods between the colored dashed lines. The time window between the dashed red lines (1735 to 1950 s) captures lower-mantle P′•d•P′ waves, the window between the dashed blue lines (2260 to 2300 s) captures several branches of PKKKP, and the time window between the dashed green lines (2320 to 2420 s) brackets upper-mantle P′•d•P′ waves. Note that slowness and back-azimuth deviations in these recordings are expected due to the complicated lateral variations in crustal structure beneath LASA (e.g., Greenfield and Sheppard, 1969; Iyer, 1971).

Array beam and slowness plots of PKKKP and P ′ • d • P ′ waves for ev... Available to Purchase

Published: 01 December 2011
, the window between the dashed blue lines (2260 to 2300 s) captures several branches of PKKKP , and the time window between the dashed green lines (2320 to 2420 s) brackets upper-mantle P ′ • d • P ′ waves. Note that slowness and back-azimuth deviations in these recordings are expected due
Image
Deviation of Lg coda from the theoretical event back azimuth (BAZ) (a) eastward or (b) westward for two earthquakes recorded by KKAR. (Top) Each detection dot is characterized by a back azimuth (given by angle), an apparent velocity (coded by color scale), and an arrival time (given by radius). The arrows indicate the direction of deviation. (Bottom) Seismogram of the central station of the array. The theoretical arrival times of Pn, Sn, and Lg waves are taken for a group velocity of 8, 4.7, and 3.5  km/s, respectively. Pn and Sn arrivals are marked by black vertical lines in the seismograms, and Lg arrival is marked by a blue vertical line and a blue circle in the seismograms and polar plots. KKAR, Karatau array.

Deviation of Lg coda from the theoretical event back azimuth (BAZ) (a) ea... Available to Purchase

Published: 24 January 2017
Figure 1. Deviation of Lg coda from the theoretical event back azimuth (BAZ) (a) eastward or (b) westward for two earthquakes recorded by KKAR. (Top) Each detection dot is characterized by a back azimuth (given by angle), an apparent velocity (coded by color scale), and an arrival time (given
Journal Article

Detailed Analysis of the Far‐Regional Seismic Coda in Kazakhstan Using Array Processing Available to Purchase

Claire Labonne, Olivier Sèbe, Alexandr Smirnov, Stéphane Gaffet, Yves Cansi, Natalya Mikhailova
Published: 24 January 2017
Bulletin of the Seismological Society of America (2017) 107 (2): 611–623.
DOI: https://doi.org/10.1785/0120160015
...Figure 6. Number of detections in the early coda as a function of (left) event longitude or (right) latitude and relative back azimuth (deviation in degree from the theoretical event back azimuth [BAZ]) for each of the five arrays. The early coda is defined as the time window between...
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View PDF for article title, Detailed Analysis of the Far‐Regional Seismic Coda in Kazakhstan Using Array Processing
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Journal Article

Back‐Azimuth Estimation of Air‐to‐Ground Coupled Infrasound from Transverse Coherence Minimization Open Access

Jordan W. Bishop, Matthew M. Haney, David Fee, Robin S. Matoza, Kathleen F. McKee, John J. Lyons
Published: 02 October 2023
The Seismic Record (2023) 3 (4): 249–258.
DOI: https://doi.org/10.1785/0320230023
... weighted coherence ( C Z I = 0.85 ) and then returns to ∼57° with decreasing coherence ( C Z I = 0.48 ; Fig.  3k ). The back‐azimuth estimate at the maximum mean weighted coherence (53°) is deviated ∼1° from the source back‐azimuth (52°). Figure 3. Transverse coherence...
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View PDF for article title, <span class="search-highlight">Back</span>‐<span class="search-highlight">Azimuth</span> Estimation of Air‐to‐Ground Coupled Infrasound from Transverse Coherence Minimization
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Journal Article

On the Importance of Using Directional Information in the Search for Lower Mantle Reflectors Open Access

Federica Rochira, Christine Thomas
Published: 18 April 2023
The Seismic Record (2023) 3 (2): 96–104.
DOI: https://doi.org/10.1785/0320220038
..., we measure slowness, back azimuth, and travel time of the signals, and use this information to backproject to the point of reflection. In our test dataset, we observe deviations from the predicted values in slowness and back azimuth in the range of 0.1–2.3 s/° and 1–20°, respectively. These values...
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View PDF for article title, On the Importance of Using Directional Information in the Search for Lower Mantle Reflectors
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Image
P‐wave particle motion recorded at KO.SVAN station for (a) 92 events from BAZ1 and (b) 34 events from BAZ2 directions. Black dashed lines show the mean apparent back‐azimuth obtained from P‐wave particle motion from multiple events (blue lines) using the principal component analysis (PCA). Red line shows the mean theoretical back‐azimuth for the group of events calculated by the station and earthquake location parameters. In the case of a correctly oriented sensor, black and red lines (mean apparent and theoretical back‐azimuth lines) overlap. The sensor deviation angle for the station is 8.4°±1.9° and 12.2°±1.9° for BAZ1 and BAZ2, respectively. (c) Rayleigh‐wave polarization results (median 9.0°, mean 6.4°±8.0°) for the same station obtained from 36 events. The gray area indicates the standard deviation around the mean. Mean and standard deviation are influenced by the back‐azimuthal range between 80° and 110°, whereas the median value of the Rayleigh‐wave method and the result of the P‐wave method show comparable results. The color version of this figure is available only in the electronic edition.

P ‐wave particle motion recorded at KO.SVAN station for (a) 92 events from ... Available to Purchase

Published: 27 January 2021
deviation around the mean. Mean and standard deviation are influenced by the back‐azimuthal range between 80° and 110°, whereas the median value of the Rayleigh‐wave method and the result of the P ‐wave method show comparable results. The color version of this figure is available only in the electronic
Image
Distributions of back‐azimuth errors corresponding to the frequency bandwidths. (a) Back‐azimuth errors at each passband. The back‐azimuth errors are denoted by gray circles. Error bars were plotted using the average and standard deviation obtained from the errors at each passband. (b) Accuracy of back‐azimuth estimation by applying single (gray box plots) and multiple (black box plots) passband to the automatic array system. At the right side of each box plot, information such as maximum (max), upper quartile (Q3), median (med), lower quartile (Q1), minimum (min), and number of data (N) are provided.

Distributions of back‐azimuth errors corresponding to the frequency bandwid... Available to Purchase

Published: 17 February 2023
Figure 6. Distributions of back‐azimuth errors corresponding to the frequency bandwidths. (a) Back‐azimuth errors at each passband. The back‐azimuth errors are denoted by gray circles. Error bars were plotted using the average and standard deviation obtained from the errors at each passband. (b
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Plot to show possible refraction and departure from plane‐wave behavior. (a) Ratio of peak transverse strain Ett to peak radial strain Err, for coordinates oriented to the back azimuth to the earthquake. (b) The same ratio, but for coordinates rotated to minimize this ratio. (c) Difference between the back azimuth and the direction that minimizes the ratio; because the strains are the same for directions 180° apart, the maximum deviation is 90°. In all panels, the large square at 236° back azimuth is for the Samoa earthquake on day 272, 2009, and the large square at 133° back azimuth is for the Peru earthquake on 174, 2001 (see Fig. 6). Table S7 lists the ratios for the back azimuth and the azimuth giving the smallest transverse strains.

Plot to show possible refraction and departure from plane‐wave behavior. (a... Available to Purchase

Published: 22 July 2014
. (c) Difference between the back azimuth and the direction that minimizes the ratio; because the strains are the same for directions 180° apart, the maximum deviation is 90°. In all panels, the large square at 236° back azimuth is for the Samoa earthquake on day 272, 2009, and the large square at 133
Image
Plot to show possible refraction and departure from plane‐wave behavior. (a) Ratio of peak transverse strain Ett to peak radial strain Err, for coordinates oriented to the back azimuth to the earthquake. (b) The same ratio, but for coordinates rotated to minimize this ratio. (c) Difference between the back azimuth and the direction that minimizes the ratio; because the strains are the same for directions 180° apart, the maximum deviation is 90°. In all panels, the large square at 236° back azimuth is for the Samoa earthquake on day 272, 2009, and the large square at 133° back azimuth is for the Peru earthquake on 174, 2001 (see Fig. 6). Table S7 lists the ratios for the back azimuth and the azimuth giving the smallest transverse strains.

Plot to show possible refraction and departure from plane‐wave behavior. (a... Available to Purchase

Published: 22 July 2014
. (c) Difference between the back azimuth and the direction that minimizes the ratio; because the strains are the same for directions 180° apart, the maximum deviation is 90°. In all panels, the large square at 236° back azimuth is for the Samoa earthquake on day 272, 2009, and the large square at 133
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Analysis of measurements on stations QHDCD and NXHYU. (a) The upper two panels depict the distribution of events used for annual measurements from 2014 to 2022. The colored circles denote PCA measurements, and the inverted triangle denotes the station. The lower panel depicts the overall measurements over 2018–2019. (b) Deviation of measurement varies with back azimuth for station QHDCD. The gray solid circles denote individual measurements based on each event. The red solid lines denote the optimized periodic function. (c) Deviation of measurement varies with back azimuth for station NXHYU. The color version of this figure is available only in the electronic edition.

Analysis of measurements on stations QHDCD and NXHYU. (a) The upper two pan... Available to Purchase

Published: 18 October 2024
the overall measurements over 2018–2019. (b) Deviation of measurement varies with back azimuth for station QHDCD. The gray solid circles denote individual measurements based on each event. The red solid lines denote the optimized periodic function. (c) Deviation of measurement varies with back azimuth
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(a,d,g,j) Beamforming summary showing the beams. (b,e,h,k) back azimuths. (c,f,i,l) Slownesses for which the main Pdiff phase (black waveforms/circles) and Pdiff+ postcursor (waveforms/triangles color‐coded by event) have their strongest energy. The back azimuth (Baz) deviation in panels (b,e,h,k) is with respect to the source back azimuth. The red dashed line in each panel indicates the source–ULVZ azimuth. The curved lines in panels (a,d,g,j) mark the Pdiff+ arrival times for the ULVZ proposed by Li et al. (2022), predicted by the 2DWT (Hauser et al., 2008) for 10% (yellow), 20% (light orange), and 30% (dark orange) reductions in VP. The black vertical dashed lines at 10 s in panels (a,d,g,j) separate the main stacks from the postcursor stacks.

(a,d,g,j) Beamforming summary showing the beams. (b,e,h,k) back azimuths. (... Open Access

Published: 06 September 2024
(Baz) deviation in panels (b,e,h,k) is with respect to the source back azimuth. The red dashed line in each panel indicates the source–ULVZ azimuth. The curved lines in panels (a,d,g,j) mark the P diff + arrival times for the ULVZ proposed by Li et al. (2022) , predicted by the 2DWT
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Diagram showing the coordinate systems and relationship between seismometer components and seismic signals. The clockwise deviation angle from the geographic north (North) to the sensor orientation (BHN) is called the station misorientation angle (φ), θc is the back azimuth calculated from source–station along the great circle path, and θa is the measured back azimuth with P wave and Rayleigh‐wave particle motion (modified from Niu and Li, 2011; Wang et al., 2016).

Diagram showing the coordinate systems and relationship between seismometer... Available to Purchase

Published: 19 January 2024
Figure 2. Diagram showing the coordinate systems and relationship between seismometer components and seismic signals. The clockwise deviation angle from the geographic north (North) to the sensor orientation (BHN) is called the station misorientation angle ( φ ), θ c is the back
Journal Article

Event Location with Sparse Data: When Probabilistic Global Search is Important Available to Purchase

Stephen Arrowsmith, Junghyun Park, Il‐Young Che, Brian Stump, Gil Averbuch
Published: 30 December 2020
Seismological Research Letters (2021) 92 (2A): 976–985.
DOI: https://doi.org/10.1785/0220200292
...Figure 5. The effect of correcting for wind bias on infrasound location accuracy. (a) Predicted back‐azimuth deviation (colored dots) from ray tracing at predicted ground intercepts for a source at the true location. Posterior density functions over epicenter using (b) uncorrected infrasound back...
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View PDF for article title, Event Location with Sparse Data: When Probabilistic Global Search is Important
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BSRN results from all processed events (open symbols) and from events passing automatic quality criteria (green solid fill). The sensor orientation of −3.0°±0.6° is the average of the 55 solid estimates. (a–c) Only larger events with high NXcr and T2R pass the criteria resulting in highly consistent orientation estimates. (a) NXcr versus magnitude, (b) NXCr versus T2R, (c) T2R versus magnitude. (d–f) Sensor misorientation (true back‐azimuth BAZ vs. estimated back‐azimuth ObsBAZ) on y axis versus (d) magnitude, (e) back azimuth, and (f) distance. Red solid line is average whereas dashed lines are 2‐σ standard deviations of mean (red) and of standard deviation (blue). Squares for M≥5.4; circles for 5.2≤M&lt;5.4; diamonds for 5.0≤M&lt;5.2; triangles for 4.8≤M&lt;5.0; and inverted triangle for M≤4.8. The color version of this figure is available only in the electronic edition.

BSRN results from all processed events (open symbols) and from events passi... Available to Purchase

Published: 01 April 2020
the criteria resulting in highly consistent orientation estimates. (a) NXcr versus magnitude, (b) NXCr versus T 2 R , (c)  T 2 R versus magnitude. (d–f) Sensor misorientation (true back‐azimuth BAZ vs. estimated back‐azimuth ObsBAZ) on y axis versus (d) magnitude, (e) back azimuth, and (f
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The coordinate systems and wave‐propagation direction (particle‐motion direction or polarization) from source to station in an ideal Earth. The clockwise deviation angle between geographic north (north) and sensor orientation (BHN) is defined as the misorientation (). θc is the back azimuth, calculated from source–station geometry, and θa is the back azimuth measured from P‐wave particle motion (modified from Niu and Li, 2011).

The coordinate systems and wave‐propagation direction (particle‐motion dire... Available to Purchase

Published: 18 May 2016
is the back azimuth, calculated from source–station geometry, and θ a is the back azimuth measured from P ‐wave particle motion (modified from Niu and Li, 2011 ).
Image
The coordinate systems and wave‐propagation direction (particle‐motion direction or polarization) from source to station in an ideal Earth. The clockwise deviation angle between geographic north (north) and sensor orientation (BHN) is defined as the misorientation (). θc is the back azimuth, calculated from source–station geometry, and θa is the back azimuth measured from P‐wave particle motion (modified from Niu and Li, 2011).

The coordinate systems and wave‐propagation direction (particle‐motion dire... Available to Purchase

Published: 18 May 2016
is the back azimuth, calculated from source–station geometry, and θ a is the back azimuth measured from P ‐wave particle motion (modified from Niu and Li, 2011 ).