%0 Journal Article %1 hough_etal:1994 %A Hough, S. E. %A Ben-Zion, Y. %A Leary, P. %D 1994 %J Bulletin of the Seismological Society of America %K geophysics seismology %N 3 %P 761--767 %T Fault-zone waves observed at the southern Joshua Tree earthquake rupture zone %U http://www.bssaonline.org/cgi/content/abstract/84/3/761 %V 84 %X Waveform and spectral characteristics of several aftershocks of the M 6.1 22 April 1992 Joshua Tree earthquake recorded at stations just north of the Indio Hills in the Coachella Valley can be interpreted in terms of waves propagating within narrow, low-velocity, high-attenuation, vertical zones. Evidence for our interpretation consists of: (1) emergent P arrivals prior to and opposite in polarity to the impulsive direct phase; these arrivals can be modeled as headwaves indicative of a transfault velocity contrast; (2) spectral peaks in the S wave train that can be interpreted as internally reflected, low-velocity fault-zone wave energy; and (3) spatial selectivity of event-station pairs at which these data are observed, suggesting a long, narrow geologic structure. The observed waveforms are modeled using the analytical solution of Ben-Zion and Aki (1990) for a plane-parallel layered fault-zone structure. Synthetic waveform fits to the observed data indicate the presence of NS-trending vertical fault-zone layers characterized by a thickness of 50 to 100 m, a velocity decrease of 10 to 15\% relative to the surrounding rock, and a P-wave quality factor in the range 25 to 50.

@article{hough_etal:1994, abstract = {Waveform and spectral characteristics of several aftershocks of the M 6.1 22 April 1992 Joshua Tree earthquake recorded at stations just north of the Indio Hills in the Coachella Valley can be interpreted in terms of waves propagating within narrow, low-velocity, high-attenuation, vertical zones. Evidence for our interpretation consists of: (1) emergent P arrivals prior to and opposite in polarity to the impulsive direct phase; these arrivals can be modeled as headwaves indicative of a transfault velocity contrast; (2) spectral peaks in the S wave train that can be interpreted as internally reflected, low-velocity fault-zone wave energy; and (3) spatial selectivity of event-station pairs at which these data are observed, suggesting a long, narrow geologic structure. The observed waveforms are modeled using the analytical solution of Ben-Zion and Aki (1990) for a plane-parallel layered fault-zone structure. Synthetic waveform fits to the observed data indicate the presence of NS-trending vertical fault-zone layers characterized by a thickness of 50 to 100 m, a velocity decrease of 10 to 15\% relative to the surrounding rock, and a P-wave quality factor in the range 25 to 50.}, added-at = {2012-09-01T13:08:21.000+0200}, author = {Hough, S. E. and Ben-Zion, Y. and Leary, P.}, biburl = {https://www.bibsonomy.org/bibtex/27190110b873a149a381b03498132d6cb/nilsma}, day = 1, interhash = {180755f0b3ae052882164b94a7a3be5c}, intrahash = {7190110b873a149a381b03498132d6cb}, journal = {Bulletin of the Seismological Society of America}, keywords = {geophysics seismology}, month = jun, number = 3, pages = {761--767}, timestamp = {2021-02-09T13:22:13.000+0100}, title = {Fault-zone waves observed at the southern Joshua Tree earthquake rupture zone}, url = {http://www.bssaonline.org/cgi/content/abstract/84/3/761}, volume = 84, year = 1994 }