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Array analysis and precise source location of deep tremor in Cascadia
Author(s)
Language
English
Obiettivo Specifico
3.2. Tettonica attiva
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/115 (2010)
Publisher
The American Geophysical Union
Issued date
June 5, 2010
Subjects
Abstract
We describe a new method to estimate the S‐P time of tremor‐like signals and its
application to the nonvolcanic tremor recorded in July 2004 by three dense arrays in
Cascadia. The cross correlation between vertical and horizontal components indicates that
very often the high‐amplitude tremor signal contains sequences of P and S waves
characterized by constant S‐P times (TS‐P) in the range 3.5–7 s. A detailed observation of
the three component seismograms stacked over the array stations confirms the presence of
P and S wave sequences. The knowledge of the TS‐P poses a strong constrain on the
source‐array distance, which dramatically reduces the uncertainty on source locations
when used with more traditional array processing techniques. Data were analyzed using
the zero lag cross‐correlation technique (ZLCC) to estimate the propagation properties
of the most correlated phases in the wavefield. Detailed polarization analyses were
computed using the covariance matrix method in the time domain. Polarization parameters,
joint with the results of ZLCC, allows for the discrimination between P and S coherent
waves. Results show that the tremor wavefield is composed mostly by shear waves,
although a consistent amount of coherent P waves is often observable. The comparison of
the back azimuth at the three arrays indicate that the source of deep tremor migrates over a
wide area, and often many independent sources located far from each other are active at
the same time. The tremor source was located by a probabilistic method that uses the
results of ZLCC, given a velocity model. When available, the inclusion of the TS‐P time in
the location procedure strongly reduces the depth range, with a distribution of hypocenters
very near the subduction interface. This result, significantly different compared with
previous less precise locations, makes the Cascadia nonvolcanic tremor more similar to the
nonvolcanic tremor recorded in Japan, at least in cases of measurable TS‐P. The
polarization azimuth aligned with the slow slip direction and the source located on the
plate interface indicate that deep tremor and slow slip are two different manifestations of a
common phenomenon related with the subduction dynamics.
application to the nonvolcanic tremor recorded in July 2004 by three dense arrays in
Cascadia. The cross correlation between vertical and horizontal components indicates that
very often the high‐amplitude tremor signal contains sequences of P and S waves
characterized by constant S‐P times (TS‐P) in the range 3.5–7 s. A detailed observation of
the three component seismograms stacked over the array stations confirms the presence of
P and S wave sequences. The knowledge of the TS‐P poses a strong constrain on the
source‐array distance, which dramatically reduces the uncertainty on source locations
when used with more traditional array processing techniques. Data were analyzed using
the zero lag cross‐correlation technique (ZLCC) to estimate the propagation properties
of the most correlated phases in the wavefield. Detailed polarization analyses were
computed using the covariance matrix method in the time domain. Polarization parameters,
joint with the results of ZLCC, allows for the discrimination between P and S coherent
waves. Results show that the tremor wavefield is composed mostly by shear waves,
although a consistent amount of coherent P waves is often observable. The comparison of
the back azimuth at the three arrays indicate that the source of deep tremor migrates over a
wide area, and often many independent sources located far from each other are active at
the same time. The tremor source was located by a probabilistic method that uses the
results of ZLCC, given a velocity model. When available, the inclusion of the TS‐P time in
the location procedure strongly reduces the depth range, with a distribution of hypocenters
very near the subduction interface. This result, significantly different compared with
previous less precise locations, makes the Cascadia nonvolcanic tremor more similar to the
nonvolcanic tremor recorded in Japan, at least in cases of measurable TS‐P. The
polarization azimuth aligned with the slow slip direction and the source located on the
plate interface indicate that deep tremor and slow slip are two different manifestations of a
common phenomenon related with the subduction dynamics.
References
Del Pezzo, E., M. La Rocca, and J. Ibanez (1997), Observation of high frequency
waves using dense arrays at Teide Volcano, Bull. Seismol. Soc.
Am., 87, 1637–1647.
Dragert, H., K. Wang, and T. S. James (2001), A silent slip event on the
deeper Cascadia subduction interface, Science, 292, 1525–1528,
doi:10.1126/science.1060152.
Frankel, A., S. Hough, P. Friberg, and R. Busby (1991), Observations of
Loma Prieta aftershocks from a dense array in Sunnyvale, California,
Bull. Seismol. Soc. Am., 81, 1900–1922.
Gomberg, J., J. L. Rubinstein, Z. Peng, K. C. Creager, J. E. Vidale, and
P. Bodin (2007), Widespread triggering of nonvolcanic tremor in California,
Science, doi:10.1126/science.1149164.
Jurkevics, A. (1988), Polarization analysis of three‐component array data,
Bull. Seismol. Soc. Am., 78(5), 1725–1743.
Kao, H., S.‐J. Shan, H. Dragert, G. Rogers, J. F. Cassidy, andK. Ramachandran
(2005), A wide depth distribution of seismic tremors along the northern
Cascadia margin, Nature, 436, doi:10.1038/nature03903.
Kao, H., S.‐J. Shan, H. Dragert, G. Rogers, J. F. Cassidy, K. Wang, T. S.
James, and K. Ramachandran (2006), Spatial‐temporal patterns of seismic
tremors in northern Cascadia, J. Geophys. Res., 111, B03309,
doi:10.1029/2005JB003727.
Kao, H., S. Shan, G. Rogers, and H. Dragert (2007), Migration characteristics
of seismic tremors in the northern Cascadia margin, Geophys. Res.
Lett. 34, L03304, doi:10.1029/2006GL028430.
La Rocca, M., G. Saccorotti, E. Del Pezzo, and J. Ibanez (2004), Probabilistic
source location of explosion quakes at Stromboli Volcano estimated
with multiple array data, J. Volcanol. Geotherm. Res., 131, 123–142,
doi:10.1016/S0377-0273(03)00321-4.
La Rocca, M., W. McCausland, D. Galluzzo, S. Malone, G. Saccorotti, and
E. Del Pezzo (2005), Array measurements of deep tremor signals in the
Cascadia subduction zone, Geophys. Res. Lett., 32, L21319, doi:10.1029/
2005GL023974.
La Rocca, M., D. Galluzzo, S. Malone, W. McCausland, G. Saccorotti, and
E. Del Pezzo (2008), Testing of small‐aperture array analysis using welllocated
earthquakes, and application to the location of deep tremor, Bull.
Seismol. Soc. Am., 98(2), doi:10.1785/0120060185.
La Rocca, M., K. C. Creager, D. Galluzzo, S. Malone, J. E. Vidale, J. R.
Sweet, and A. G. Wech (2009), Cascadia tremor located near plate interface
constrained by S minus P wave times, Science, 323, 620–623,
doi:10.1126/science.1167112.
McCausland, W. (2006), Tracking subduction tremor in Cascadia using
regional network and small aperture seismic array data, Ph.D. dissertation,
Univ. of Wash., Seattle.
McCausland, W., S. Malone, and D. Johnson (2005), Temporal and spatial
occurrence of deep nonvolcanic tremor: From Washington to northern
California, Geophys. Res. Lett., 32, L24311, doi:10.1029/2005GL024349.
McCausland, W., K. C. Creager, M. La Rocca, and S. Malone (2010),
Short‐term and long‐term tremor migration patterns of the Cascadia
2004 tremor and slow slip episode using small aperture seismic arrays,
J. Geophys. Res., doi:10.1029/2008JB006063, in press. Melbourne, T. I., W. M. Szeliga, M. M. Miller, and V. M. Santillan (2005),
Extent and duration of the 2003 Cascadia slow earthquake, Geophys.
Res. Lett., 32, L04301, doi:10.1029/2004GL021790.
Nadeau, R. M., and D. Dolenc (2005), Nonvolcanic tremors deep beneath
the San Andreas fault, Science, 307, 389, doi:10.1126/science.1107142.
Obara, K. (2002), Nonvolcanic deep tremor associated with subduction in
southwest Japan, Science, 296, 1679–1681, doi:10.1126/science.1070378.
Obara, K., and H. Hirose (2006), Nonvolcanic deep low‐frequency tremors
accompanying slow slips in the southwest Japan subduction zone,
Tectonophysics, 417, 33–51, doi:10.1016/j.tecto.2005.04.013.
Payero, J. S., V. Kostoglodov, N. Shapiro, T. Mikumo, A. Iglesias, X. Pérez‐
Campos, and R. W. Clayton (2008), Nonvolcanic tremor observed in
the Mexican subduction zone, Geophys. Res. Lett., 35, L07305,
doi:10.1029/2007GL032877.
Preston, L. A., K. C. Creager, R. S. Crosson, T. M. Brocher, and A. M. Trehu
(2003), Intraslab earthquakes: Dehydration of the Cascadia slab, Science,
302, 1197–1200, doi:10.1126/science.1090751.
Rogers, G., and H. Dragert (2003), Episodic tremor and slip on the Cascadia
subduction zone: The chatter of silent slip, Science, 300, 1942–1943,
doi:10.1126/science.1084783.
Royle, G. T., A. J. Calvert, and H. Kao (2006), Observations of nonvolcanic
tremor during the northern Cascadia slow‐slip event in February
2002, Geophys. Res. Lett., 33, L18313, doi:10.1029/2006GL027316.
Rubinstein, J. L., M. La Rocca, J. E. Vidale, K. C. Creager, and A. G.
Wech (2008), Tidal modulation of nonvolcanic tremor, Science, 319,
186–189, doi:10.1126/science.1150558.
Saccorotti, G., and E. Del Pezzo (2000), A probabilistic approach to the
inversion of data from a seismic array and its application to volcanic
signals, Geophys. J. Int., 143, 249–261, doi:10.1046/j.1365-
246x.2000.00252.x.
Schwartz, S. Y., and J. M. Rokosky (2007), Slow slip events and seismic
tremor at circum‐pacific subduction zones, Rev. Geophys., 45, RG3004,
doi:10.1029/2006RG000208.
Shelly, D. R., G. C. Beroza, and S. Ide (2006), Low‐frequency earthquakes
in Shikoku, Japan, and their relationship to episodic tremor and slip,
Nature, 442, 188–191, doi:10.1038/nature04931.
Wech, A. G., and K. C. Creager (2007), Cascadia tremor polarization evidence
for plate interface slip, Geophys. Res. Lett., 34, L22306,
doi:10.1029/2007GL031167.
Wessel, P., and W. H. F. Smith (1998), New, improved version of the
Generic Mapping Tools released, Eos Trans. AGU, 79(47), 579,
doi:10.1029/98EO00426.
waves using dense arrays at Teide Volcano, Bull. Seismol. Soc.
Am., 87, 1637–1647.
Dragert, H., K. Wang, and T. S. James (2001), A silent slip event on the
deeper Cascadia subduction interface, Science, 292, 1525–1528,
doi:10.1126/science.1060152.
Frankel, A., S. Hough, P. Friberg, and R. Busby (1991), Observations of
Loma Prieta aftershocks from a dense array in Sunnyvale, California,
Bull. Seismol. Soc. Am., 81, 1900–1922.
Gomberg, J., J. L. Rubinstein, Z. Peng, K. C. Creager, J. E. Vidale, and
P. Bodin (2007), Widespread triggering of nonvolcanic tremor in California,
Science, doi:10.1126/science.1149164.
Jurkevics, A. (1988), Polarization analysis of three‐component array data,
Bull. Seismol. Soc. Am., 78(5), 1725–1743.
Kao, H., S.‐J. Shan, H. Dragert, G. Rogers, J. F. Cassidy, andK. Ramachandran
(2005), A wide depth distribution of seismic tremors along the northern
Cascadia margin, Nature, 436, doi:10.1038/nature03903.
Kao, H., S.‐J. Shan, H. Dragert, G. Rogers, J. F. Cassidy, K. Wang, T. S.
James, and K. Ramachandran (2006), Spatial‐temporal patterns of seismic
tremors in northern Cascadia, J. Geophys. Res., 111, B03309,
doi:10.1029/2005JB003727.
Kao, H., S. Shan, G. Rogers, and H. Dragert (2007), Migration characteristics
of seismic tremors in the northern Cascadia margin, Geophys. Res.
Lett. 34, L03304, doi:10.1029/2006GL028430.
La Rocca, M., G. Saccorotti, E. Del Pezzo, and J. Ibanez (2004), Probabilistic
source location of explosion quakes at Stromboli Volcano estimated
with multiple array data, J. Volcanol. Geotherm. Res., 131, 123–142,
doi:10.1016/S0377-0273(03)00321-4.
La Rocca, M., W. McCausland, D. Galluzzo, S. Malone, G. Saccorotti, and
E. Del Pezzo (2005), Array measurements of deep tremor signals in the
Cascadia subduction zone, Geophys. Res. Lett., 32, L21319, doi:10.1029/
2005GL023974.
La Rocca, M., D. Galluzzo, S. Malone, W. McCausland, G. Saccorotti, and
E. Del Pezzo (2008), Testing of small‐aperture array analysis using welllocated
earthquakes, and application to the location of deep tremor, Bull.
Seismol. Soc. Am., 98(2), doi:10.1785/0120060185.
La Rocca, M., K. C. Creager, D. Galluzzo, S. Malone, J. E. Vidale, J. R.
Sweet, and A. G. Wech (2009), Cascadia tremor located near plate interface
constrained by S minus P wave times, Science, 323, 620–623,
doi:10.1126/science.1167112.
McCausland, W. (2006), Tracking subduction tremor in Cascadia using
regional network and small aperture seismic array data, Ph.D. dissertation,
Univ. of Wash., Seattle.
McCausland, W., S. Malone, and D. Johnson (2005), Temporal and spatial
occurrence of deep nonvolcanic tremor: From Washington to northern
California, Geophys. Res. Lett., 32, L24311, doi:10.1029/2005GL024349.
McCausland, W., K. C. Creager, M. La Rocca, and S. Malone (2010),
Short‐term and long‐term tremor migration patterns of the Cascadia
2004 tremor and slow slip episode using small aperture seismic arrays,
J. Geophys. Res., doi:10.1029/2008JB006063, in press. Melbourne, T. I., W. M. Szeliga, M. M. Miller, and V. M. Santillan (2005),
Extent and duration of the 2003 Cascadia slow earthquake, Geophys.
Res. Lett., 32, L04301, doi:10.1029/2004GL021790.
Nadeau, R. M., and D. Dolenc (2005), Nonvolcanic tremors deep beneath
the San Andreas fault, Science, 307, 389, doi:10.1126/science.1107142.
Obara, K. (2002), Nonvolcanic deep tremor associated with subduction in
southwest Japan, Science, 296, 1679–1681, doi:10.1126/science.1070378.
Obara, K., and H. Hirose (2006), Nonvolcanic deep low‐frequency tremors
accompanying slow slips in the southwest Japan subduction zone,
Tectonophysics, 417, 33–51, doi:10.1016/j.tecto.2005.04.013.
Payero, J. S., V. Kostoglodov, N. Shapiro, T. Mikumo, A. Iglesias, X. Pérez‐
Campos, and R. W. Clayton (2008), Nonvolcanic tremor observed in
the Mexican subduction zone, Geophys. Res. Lett., 35, L07305,
doi:10.1029/2007GL032877.
Preston, L. A., K. C. Creager, R. S. Crosson, T. M. Brocher, and A. M. Trehu
(2003), Intraslab earthquakes: Dehydration of the Cascadia slab, Science,
302, 1197–1200, doi:10.1126/science.1090751.
Rogers, G., and H. Dragert (2003), Episodic tremor and slip on the Cascadia
subduction zone: The chatter of silent slip, Science, 300, 1942–1943,
doi:10.1126/science.1084783.
Royle, G. T., A. J. Calvert, and H. Kao (2006), Observations of nonvolcanic
tremor during the northern Cascadia slow‐slip event in February
2002, Geophys. Res. Lett., 33, L18313, doi:10.1029/2006GL027316.
Rubinstein, J. L., M. La Rocca, J. E. Vidale, K. C. Creager, and A. G.
Wech (2008), Tidal modulation of nonvolcanic tremor, Science, 319,
186–189, doi:10.1126/science.1150558.
Saccorotti, G., and E. Del Pezzo (2000), A probabilistic approach to the
inversion of data from a seismic array and its application to volcanic
signals, Geophys. J. Int., 143, 249–261, doi:10.1046/j.1365-
246x.2000.00252.x.
Schwartz, S. Y., and J. M. Rokosky (2007), Slow slip events and seismic
tremor at circum‐pacific subduction zones, Rev. Geophys., 45, RG3004,
doi:10.1029/2006RG000208.
Shelly, D. R., G. C. Beroza, and S. Ide (2006), Low‐frequency earthquakes
in Shikoku, Japan, and their relationship to episodic tremor and slip,
Nature, 442, 188–191, doi:10.1038/nature04931.
Wech, A. G., and K. C. Creager (2007), Cascadia tremor polarization evidence
for plate interface slip, Geophys. Res. Lett., 34, L22306,
doi:10.1029/2007GL031167.
Wessel, P., and W. H. F. Smith (1998), New, improved version of the
Generic Mapping Tools released, Eos Trans. AGU, 79(47), 579,
doi:10.1029/98EO00426.
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