%0 Journal Article %1 li_etal:1997a %A Li, Yong-Gang %A Ellsworth, William L. %A Thurber, Clifford H. %A Malin, Peter E. %A Aki, Keiiti %D 1997 %J Bulletin of the Seismological Society of America %K geophysics seismics %N 1 %P 210--221 %T Fault-zone guided waves from explosions in the San Andreas Fault at Parkfield and Cienaga Valley, California %U http://www.bssaonline.org/cgi/content/abstract/87/1/210 %V 87 %X ault-zone guided waves were successfully excited by near-surface explosions in the San Andreas fault zone both at Parkfield and Cienega Valley, central California. The guided waves were observed on linear, three-component seismic arrays deployed across the fault trace. These waves were not excited by explosions located outside the fault zone. The amplitude spectra of guided waves show a maximum peak at 2 Hz at Parkfield and 3 Hz at Cienega Valley. The guided wave amplitude decays sharply with observation distance from the fault trace. The explosion-excited fault-zone guided waves are similar to those generated by earthquakes at Parkfield but have lower frequencies and travel more slowly. These observations suggest that the fault-zone wave guide has lower seismic velocities as it approaches the surface at Parkfield. We have modeled the waveforms as S waves trapped in a low-velocity wave guide sandwiched between high-velocity wall rocks, resulting in Love-type fault-zone guided waves. While the results are nonunique, the Parkfield data are adequately fit by a shallow wave guide 170 m wide with an S velocity 0.85 km/sec and an apparent Q 30 to 40. At Cienega Valley, the fault-zone wave guide appears to be about 120 m wide with an S velocity 0.7 km/sec and a Q 30.

@article{li_etal:1997a, abstract = {ault-zone guided waves were successfully excited by near-surface explosions in the San Andreas fault zone both at Parkfield and Cienega Valley, central California. The guided waves were observed on linear, three-component seismic arrays deployed across the fault trace. These waves were not excited by explosions located outside the fault zone. The amplitude spectra of guided waves show a maximum peak at 2 Hz at Parkfield and 3 Hz at Cienega Valley. The guided wave amplitude decays sharply with observation distance from the fault trace. The explosion-excited fault-zone guided waves are similar to those generated by earthquakes at Parkfield but have lower frequencies and travel more slowly. These observations suggest that the fault-zone wave guide has lower seismic velocities as it approaches the surface at Parkfield. We have modeled the waveforms as S waves trapped in a low-velocity wave guide sandwiched between high-velocity wall rocks, resulting in Love-type fault-zone guided waves. While the results are nonunique, the Parkfield data are adequately fit by a shallow wave guide 170 m wide with an S velocity 0.85 km/sec and an apparent Q 30 to 40. At Cienega Valley, the fault-zone wave guide appears to be about 120 m wide with an S velocity 0.7 km/sec and a Q 30.}, added-at = {2012-09-01T13:08:21.000+0200}, author = {Li, Yong-Gang and Ellsworth, William L. and Thurber, Clifford H. and Malin, Peter E. and Aki, Keiiti}, biburl = {https://www.bibsonomy.org/bibtex/217bbe404905c4148a2f249643639258a/nilsma}, day = 1, interhash = {8c18d4d8d71f9338f3a2c535c44d96ea}, intrahash = {17bbe404905c4148a2f249643639258a}, journal = {Bulletin of the Seismological Society of America}, keywords = {geophysics seismics}, month = feb, number = 1, pages = {210--221}, timestamp = {2021-02-09T13:26:58.000+0100}, title = {Fault-zone guided waves from explosions in the San Andreas Fault at Parkfield and Cienaga Valley, California}, url = {http://www.bssaonline.org/cgi/content/abstract/87/1/210}, volume = 87, year = 1997 }