Papers Published

1. Yong-Gang Li and Ellsworth, W.L. and Thurber, C.H. and Malin, P.E. and Aki, K., Fault-zone guided waves from explosions in the San Andreas fault at Parkfield and Cienega Valley, California, Bull. Seismol. Soc. Am. (USA), vol. 87 no. 1 (1997), pp. 210 - 21 .
   (last updated on 2007/04/09)

   Abstract:
   Fault-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

   Keywords:
   Earth crust;faulting;seismic waves;