| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF SOUTHERN CALIFORNIA, LOS ANGELES, CALIFORNIA 90089-0740
Abstract
Two instances of fault zone trapped seismic waves have been observed. At an active normal fault in crystalline rock near Oroville in northern California, trapped waves were excited with a surface source and recorded at five near-fault borehole depths with an oriented three-component borehole seismic sonde. At Parkfield, California, a borehole seismometer at Middle Mountain recorded at least two instances of the fundamental and first higher mode seismic waves of the San Andreas fault zone. At Oroville recorded particle motions indicate the presence of both Love and Rayleigh normal modes. The Love-wave dispersion relation derived for an idealized wave guide with velocity structure determined by body-wave travel-time inversion yields seismograms of the fundamental mode that are consistent with the observed Love-wave amplitude and frequency. Applying a similar velocity model to the Parkfield observations, we obtain a good fit to the trapped wavefield amplitude, frequency, dispersion, and mode time separation for an asymmetric San Andreas fault zone structure—a high-velocity half-space to the southwest, a low-velocity fault zone, a transition zone containing the borehole seismometer, and an intermediate velocity half-space to the northeast. In the Parkfield borehole seismic data set, the locations (depth and offset normal to fault plane) of natural seismic events which do or do not excite trapped waves are roughly consistent with our model of the low velocity zone. We conclude that it is feasible to obtain near-surface borehole records of fault zone trapped waves. Because trapped modes are excited only by events close to the fault zone proper—thereby fixing these events in space relative to the fault—a wider investigation of possible trapped mode waveforms recorded by a borehole seismic network could lead to a much refined body-wave/tomographic velocity model of the fault and to a weighting of events as a function of offset from the fault plane. It is an open question whether near-surface sensors exist in a stable enough seismic environment to use trapped modes as an earth monitoring device.
This article has been cited by other articles:
|
|
 |
|
  T. Mizuno, Y. Kuwahara, H. Ito, and K. Nishigami Spatial Variations in Fault-Zone Structure along the Nojima Fault, Central Japan, as Inferred from Borehole Observations of Fault-Zone Trapped Waves Bulletin of the Seismological Society of America, April 1, 2008; 98(2): 558 - 570. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Shakal, H. Haddadi, V. Graizer, K. Lin, and M. Huang Some Key Features of the Strong-Motion Data from the M 6.0 Parkfield, California, Earthquake of 28 September 2004 Bulletin of the Seismological Society of America, September 1, 2006; 96(4B): S90 - S118. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. R. Johnson and R. M. Nadeau Asperity Model of an Earthquake: Dynamic Problem Bulletin of the Seismological Society of America, February 1, 2005; 95(1): 75 - 108. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Can Seismic Waves Be Trapped inside an Inactive Fault Zone? The Case Study of Nocera Umbra, Central Italy Bulletin of the Seismological Society of America, August 1, 2002; 92(6): 2217 - 2232.
|
|
|
|
|
|
Study of the 1999 M 7.1 Hector Mine, California, Earthquake Fault Plane by Trapped Waves Bulletin of the Seismological Society of America, May 1, 2002; 92(4): 1318 - 1332.
|
|
|
|
|
|
Damage and Ground Shaking in the Town of Nocera Umbra during Umbria-Marche, Central Italy, Earthquakes: The Special Effect of a Fault Zone Bulletin of the Seismological Society of America, June 1, 2001; 91(3): 511 - 519.
|
|
|
|
|
|
Y.-G. Li, W. L. Ellsworth, C. H. Thurber, P. E. Malin, and K. Aki Fault-zone guided waves from explosions in the San Andreas fault at Parkfield and Cienega Valley, California Bulletin of the Seismological Society of America, February 1, 1997; 87(1): 210 - 221. [Abstract] [PDF]
|
|
|
|
|
|
J. K. Hammer and C. A. Langston Modeling the effect of San Andreas fault structure on receiver functions using elastic 3D finite difference Bulletin of the Seismological Society of America, October 1, 1996; 86(5): 1608 - 1622. [Abstract] [PDF]
|
|
|
|
|
|
Y.-G. Li and J. E. Vidale Low-velocity fault-zone guided waves: Numerical investigations of trapping efficiency Bulletin of the Seismological Society of America, April 1, 1996; 86(2): 371 - 378. [Abstract] [PDF]
|
|
|
|
|
|
B.-S. Huang, T.-l. Teng, and Y. T. Yeh Numerical modeling of fault-zone trapped waves: Acoustic case Bulletin of the Seismological Society of America, December 1, 1995; 85(6): 1711 - 1717. [Abstract] [PDF]
|
|
|
|
|
|
D. Jongmans and P. E. Malin Microearthquake S-wave observations from 0 to 1 km in the Varian well at Parkfield, California Bulletin of the Seismological Society of America, December 1, 1995; 85(6): 1805 - 1820. [Abstract] [PDF]
|
|
|
|
 |
|
 Y.-G. Li, Y.-G. Li, K. Aki, J. E. Vidale, W. H. K. Lee, and C. J. Marone Fine Structure of the Landers Fault Zone: Segmentation and the Rupture Process Science, July 15, 1994; 265(5170): 367 - 370. [Abstract] [PDF]
|
|
|
|
|
|
S. E. Hough, Y. Ben-Zion, and P. Leary Fault-zone waves observed at the southern Joshua Tree earthquake rupture zone Bulletin of the Seismological Society of America, June 1, 1994; 84(3): 761 - 767. [Abstract] [PDF]
|
|
|
|
|
|
R. Nadeau, M. Antolik, P. A. Johnson, W. Foxall, and T. V. McEvilly Seismological studies at Parkfield III: Microearthquake clusters in the study of fault-zone dynamics Bulletin of the Seismological Society of America, April 1, 1994; 84(2): 247 - 263. [Abstract] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
