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coda length

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Journal Article

A Coda-Length Magnitude Scale For New England

M. P. Chaplin, S. R. Taylor, M. N. Toksöz
Published: 01 October 1980
Seismological Research Letters (1980) 51 (4): 15–22.
DOI: https://doi.org/10.1785/gssrl.51.4.15
...M. P. Chaplin; S. R. Taylor; M. N. Toksöz Abstract An empirical coda-length (signa] duration) magnitude scale is developed to estimate magnitudes for earthquakes in New England. The formula is based on the mean signal duration, T (in seconds), measured from 45 local earthquakes and is given by: m b...
View PDF for article title, A <span class="search-highlight">Coda</span>-<span class="search-highlight">Length</span> Magnitude Scale For New England
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Trilinear regression between the moment magnitudes and coda length (equation 10) of the detected seismic events (and their distribution on top and right of the figure, respectively) obtained for this case study located in the western Canada sedimentary basin (WCSB, see the complete seismic catalog in Ⓔ Table S1) compared with other coda‐magnitude scales reported for other sites of the world (summarized in Table 1) and with the IS‐TLP for the province of Alberta, where any seismic event of magnitude ≥2.0 must be reported to the regulator (Shipman et al., 2018). The color version of this figure is available only in the electronic edition.

Trilinear regression between the moment magnitudes and coda length (equatio...

Published: 03 April 2019
Figure 8. Trilinear regression between the moment magnitudes and coda length (equation  10 ) of the detected seismic events (and their distribution on top and right of the figure, respectively) obtained for this case study located in the western Canada sedimentary basin (WCSB, see the complete
Image
Well-located coda-length magnitude ≥2.3 earthquakes, January 1976 through May 2001, as determined by the Pacific Northwest Seismograph Network. Black bars show the orientation of P axes as determined by routine first-motion analysis of well-located events with shallow P axes (plunge ≤ 30°). Most first-motion solutions have shallow P axes; only one event is omitted because of steep P-axis plunge.

Well-located coda-length magnitude ≥2.3 earthquakes, January 1976 through M...

Published: 01 December 2002
Figure 9. Well-located coda-length magnitude ≥2.3 earthquakes, January 1976 through May 2001, as determined by the Pacific Northwest Seismograph Network. Black bars show the orientation of P axes as determined by routine first-motion analysis of well-located events with shallow P axes (plunge
Journal Article

Simultaneous inversion for Q and source parameters of microearthquakes accompanying hydraulic fracturing in granitic rock

Michael Fehler, W. Scott Phillips
Published: 01 April 1991
Bulletin of the Seismological Society of America (1991) 81 (2): 553–575.
DOI: https://doi.org/10.1785/BSSA0810020553
... drops were found to be larger near the edges of the seismic zone, in regions that had not been seismically active during previous injections. The seismic moments determined from spectra were used to obtain a coda length-to-moment relation. Then, moments were estimated for 1149 events from measurements...
View PDF for article title, Simultaneous inversion for Q and source parameters of microearthquakes accompanying hydraulic fracturing in granitic rock
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Journal Article

Source spectra of great earthquakes: Teleseismic constraints on rupture process and strong motion

Heidi Houston, Hiroo Kanamori
Published: 01 February 1986
Bulletin of the Seismological Society of America (1986) 76 (1): 19–42.
DOI: https://doi.org/10.1785/BSSA0760010019
... parameters are measured from the short-period P -wave train: the maximum amplitude; the period at maximum amplitude; the time between the first arrival and when the maximum amplitude is attained; and coda length. An extension, m^ b , of the teleseismic magnitude, m b , is defined using the maximum amplitude...
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Journal Article

Sensitivity and Stability Analysis of Coda Quality Factors at The Geysers Geothermal Field, California

Aglaja Blanke, Grzegorz Kwiatek, Patricia Martínez‐Garzón, Marco Bohnhoff
Published: 09 April 2019
Bulletin of the Seismological Society of America (2019) 109 (3): 959–975.
DOI: https://doi.org/10.1785/0120180219
..., including lapse time, magnitude range, moving window width, total coda length, and seismic‐sensor components. The choice of quality criteria—signal‐to‐noise ratio and coda Q uncertainties ( 2 σ ( Q C ( f ) ) )—are found to be most sensitive factors. Testing different window lengths and lapse times results...
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View PDF for article title, Sensitivity and Stability Analysis of <span class="search-highlight">Coda</span> Quality Factors at The Geysers Geothermal Field, California
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Journal Article

Propagation of Crustal-Waveguide-Trapped Pg and Seismic Velocity Structure in the South Indian Shield

V. G. Krishna, D. S. Ramesh
Published: 01 October 2000
Bulletin of the Seismological Society of America (2000) 90 (5): 1281–1294.
DOI: https://doi.org/10.1785/0119990028
... and the coda in the few available seismograms at offsets greater than 220 km ( Fig. 2 ) may indicate a very irregular distribution of scatterers and a short horizontal correlation length. Alternatively, since the travel paths involved for these distances are from KUD to GBA, which seem to cross the Closepet...
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View PDF for article title, Propagation of Crustal-Waveguide-Trapped Pg and Seismic Velocity Structure in the South Indian Shield
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Journal Article

Microearthquake survey of the Miramichi, New Brunswick, epicentral region, 1985

Kenneth B. S. Burke, Robert J. Wetmiller, Maurice Lamontagne, M. Jeffrey Carr, Craig Hickey
Published: 01 December 1989
Canadian Journal of Earth Sciences (1989) 26 (12): 2567–2577.
DOI: https://doi.org/10.1139/e89-219
.... The activity was episodic, with days of few earthquakes being followed by periods when events clustered together in miniswarms. Coda-magnitude relationships for five stations were established from regression analysis of scaled coda lengths of events on the MEQ 800 records and Nuttli magnitudes determined...
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Journal Article

Microearthquake distribution and mechanisms of faulting in the Fontana-San Bernardino area of Southern California

David Hadley, Jim Combs
Published: 01 October 1974
Bulletin of the Seismological Society of America (1974) 64 (5): 1477–1499.
DOI: https://doi.org/10.1785/BSSA0640051477
... a magnitude scale (1.5 to 3.3) based on coda lengths recorded by instruments peaked at 20 Hz. Forty-five hypocenters from the analysis of over 6,000 hr of low-noise records define two northeast trending lineations within the western portion of the Valley. A composite first-motion plot of 22 microearthquakes...
View PDF for article title, Microearthquake distribution and mechanisms of faulting in the Fontana-San Bernardino area of Southern California
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Journal Article

Small earthquakes, structure, and tectonics of the Puget Sound region

Robert S. Crosson
Published: 01 October 1972
Bulletin of the Seismological Society of America (1972) 62 (5): 1133–1171.
DOI: https://doi.org/10.1785/BSSA0620051133
..., earthquakes are reliably located as deep as 50 km and a few isolated events may be deeper. No strong lineations are observed in the pattern of hypocenters, although there are some general zones of high activity within the array. Magnitude estimates are successfully based on a coda-length scheme. Recurrence...
View PDF for article title, Small earthquakes, structure, and tectonics of the Puget Sound region
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QC‾(f) curves with st. dev. (error bars) per center frequency for (a) station HVC and (b) station FNF. Different line styles indicate tested total coda lengths of 6 and 10 s duration.

Q C ‾ ( f ) curves with st. dev. (error bars) per center frequenc...

Published: 09 April 2019
Figure 7. Q C ‾ ( f ) curves with st. dev. (error bars) per center frequency for (a) station HVC and (b) station FNF. Different line styles indicate tested total coda lengths of 6 and 10 s duration.
Image
Coda magnitudes of the Rangely events. (a) Magnitude–frequency distribution of the Rangely events. Open triangles are number of events in each 0.1 magnitude bin. The red squares show the distribution of the cumulative number of events larger than each magnitude bin. The black line shows the b‐value fit, and the magnitude of completeness is marked at the top. (b) Magnitude–time plot of the Rangely events. Magnitude is coda length magnitude defined by Mc=1.8log10T−1.0. Symbol size is proportional to event magnitude. The color version of this figure is available only in the electronic edition.

Coda magnitudes of the Rangely events. (a) Magnitude–frequency distribution...

Published: 01 July 2022
shows the b ‐value fit, and the magnitude of completeness is marked at the top. (b) Magnitude–time plot of the Rangely events. Magnitude is coda length magnitude defined by M c = 1.8 log 10 T − 1.0 . Symbol size is proportional to event magnitude. The color version of this figure
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Example of accelerometric records (in black) for the 15 November 2007 event of magnitude 4.3 located 13 km to the west-southwest of Bagnères (east component). Station codes refer to Figure 2c. Ground velocity is plotted in gray to make the low frequencies more apparent. Note the strong variations in amplitude, frequency content, and coda length.

Example of accelerometric records (in black) for the 15 November 2007 event...

Published: 01 August 2011
the strong variations in amplitude, frequency content, and coda length.
Image
κ0coda of all stations as a function of coda window length for different choices of the coda onset for (a) Tcoda=20  s, (b) Tcoda=40  s, and (c) Tcoda=2.3(TS−TP)+TS (black lines) after the origin time of the earthquake. Epicentral distances range between 5 and 120 km. Light line represents the mean ± one standard deviation. The color version of this figure is available only in the electronic edition.

κ 0 coda of all stations as a function of coda window length for diff...

Published: 18 June 2019
Figure 4. κ 0 coda of all stations as a function of coda window length for different choices of the coda onset for (a)  T coda = 20    s , (b)  T coda = 40    s , and (c)  T coda = 2.3 ( T S − T P ) + T S (black lines) after the origin
Image
Relationships between various magnitudes for earthquakes in the study area. Solid lines denote equal values of quantities on two axes. (a) mf determined from felt area using the relationship in Figure 4 as a function of mbLg. Arrows indicate mf or mbLg values likely are minima based on poorly defined felt area or small seismic signals. (b) mf, mbLg, and ML as a function of coda-length magnitude, Mc. (c) mbLg measured near 1 Hz; ML and mf as a function of Mn (mbLg determined between about 3 and 10 Hz). (d) mbLg, ML, and mf as a function of maximum intensity on MM scale. Intensity 1 indicates not felt.

Relationships between various magnitudes for earthquakes in the study area....

Published: 01 August 2008
likely are minima based on poorly defined felt area or small seismic signals. (b)  m f , m b Lg , and M L as a function of coda-length magnitude, M c . (c)  m b Lg measured near 1 Hz; M L and m f as a function of M n ( m b Lg determined between about 3 and 10 Hz). (d)  m b Lg
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Used window length of the P-wave coda as a function of epicentral distance. The traveltime curves are drawn using the regional velocity model from Farías et al. (2010) for depths down to 110 km and the ak135 model (Kennett et al., 1995) for greater depths. Light gray rectangular indicates the used epicentral distance, whereas the dark gray area indicates the window lengths to be extracted for an earthquake characterized by a source depth of 100 km.

Used window length of the P-wave coda as a function of epicentral distance....

Published: 08 June 2016
Figure 5. Used window length of the P-wave coda as a function of epicentral distance. The traveltime curves are drawn using the regional velocity model from Farías et al. (2010) for depths down to 110 km and the ak135 model ( Kennett et al., 1995 ) for greater depths. Light gray rectangular
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Q0 and η values versus the length of coda window.The color version of this figure is available only in the electronic edition.

Q 0 and η values versus the length of coda window.The color version of ...

Published: 07 June 2016
Figure 7. Q 0 and η values versus the length of coda window.The color version of this figure is available only in the electronic edition.
Image
Qc as a function of the length of the coda window LW, measured at 6 Hz in the Pyrenees. Two examples of coda onset are shown: (a) tW=30  s and (b) tW=50  s after the origin time of the earthquake. Epicentral distances range between 50 and 80 km.

Q c as a function of the length of the coda window L W , measured a...

Published: 01 June 2013
Figure 2. Q c as a function of the length of the coda window L W , measured at 6 Hz in the Pyrenees. Two examples of coda onset are shown: (a)  t W =30  s and (b)  t W =50  s after the origin time of the earthquake. Epicentral distances range between 50 and 80 km.
Image
Schematic ray paths illustrate possible models for coda. (1) The coda scatter or take a longer refracted path in the deep subsurface. The direct coda ray has the same path length as the primary ray in the shallow subsurface. Energy from both primary and coda rays briefly reverberates in the shallow subsurface. (2) The addition path length of a coda ray is confined to the shallow subsurface. (3) A coda ray is scattered off the free surface and produces a surface wave. Model (1) is the most compatible with observations. See text.

Schematic ray paths illustrate possible models for coda. (1) The coda scatt...

Published: 01 October 2009
Figure 2. Schematic ray paths illustrate possible models for coda. (1) The coda scatter or take a longer refracted path in the deep subsurface. The direct coda ray has the same path length as the primary ray in the shallow subsurface. Energy from both primary and coda rays briefly reverberates
Image
Deviation of κ0,coda from the value of κ0,coda that is used in this study according to equation (9) for (a) different choices of the coda wave onset time chosen between 10 and 50 s (given as lapse time after the event origin time) and (b) different choices of the coda window length selected between 10 and 50 s. The deviation is given from the value of κ0,coda computed for a variable coda‐wave onset time following equation (8) and a fixed coda window length of 20 s (coda‐wave window definition used in this study). The thin gray lines correspond to the different Kiban–Kyoshin network (KiK‐net) sites used in this study. The thick solid and dashed lines are the mean and standard deviation computed from all sites. Only events with an epicentral distance smaller than 50 km are used for this figure. The color version of this figure is available only in the electronic edition.

Deviation of κ 0 , coda from the value of κ 0 , coda ...

Published: 10 August 2023
choices of the coda window length selected between 10 and 50 s. The deviation is given from the value of κ 0 , coda computed for a variable coda‐wave onset time following equation  (8) and a fixed coda window length of 20 s (coda‐wave window definition used in this study). The thin gray