%0 Journal Article %1 malin_etal:1996 %A Malin, P. E. %A Lou, M. %A Rial, J. A. %D 1996 %J Geophysical Research Letters %K geophysics seismology %N 24 %P 3547--3550 %R 10.1029/96GL03424 %T Fr waves: A second fault-guided mode with implications for fault property studies %U http://dx.doi.org/10.1029/96GL03424 %V 23 %X Previous work has shown that earthquake S-waves can become fault zone guided-waves. We present observational evidence for a second type of earthquake-generated, fault-guided seismic wave, apparently involving coupled P- and S-waves. Our data are from a fault located in igneous rocks in Owens Valley, California. In analogy to standard Love and Rayleigh waves, we suggest that purely S-type modes be indicated on seismograms by "FL" and the new coupled P- and S-type by "FR". Since FR waves are sensitive to both the local P- and S-wave velocities, their presence implies unique conditions in and near the fault. Modeling of our seismograms suggests a differential reduction in these velocities, with a larger change in bulk modulus than in shear modulus. We propose that this reduction is due to unsaturated fractures within the core of the fault. We view FR waves as a new tool for detecting and characterizing highly fractured fault zones, providing important information on the relation of earthquakes and subsurface fluid conduits.

@article{malin_etal:1996, abstract = {Previous work has shown that earthquake S-waves can become fault zone guided-waves. We present observational evidence for a second type of earthquake-generated, fault-guided seismic wave, apparently involving coupled P- and S-waves. Our data are from a fault located in igneous rocks in Owens Valley, California. In analogy to standard Love and Rayleigh waves, we suggest that purely S-type modes be indicated on seismograms by "FL" and the new coupled P- and S-type by "FR". Since FR waves are sensitive to both the local P- and S-wave velocities, their presence implies unique conditions in and near the fault. Modeling of our seismograms suggests a differential reduction in these velocities, with a larger change in bulk modulus than in shear modulus. We propose that this reduction is due to unsaturated fractures within the core of the fault. We view FR waves as a new tool for detecting and characterizing highly fractured fault zones, providing important information on the relation of earthquakes and subsurface fluid conduits.}, added-at = {2012-09-01T13:08:21.000+0200}, author = {Malin, P. E. and Lou, M. and Rial, J. A.}, biburl = {https://www.bibsonomy.org/bibtex/2b5b28a3bfc8fc6072d081b35503d597a/nilsma}, doi = {10.1029/96GL03424}, interhash = {74f27bf10258dc7a891d4e59d1c71e13}, intrahash = {b5b28a3bfc8fc6072d081b35503d597a}, issn = {0094-8276}, journal = {Geophysical Research Letters}, keywords = {geophysics seismology}, number = 24, pages = {3547--3550}, timestamp = {2021-02-09T13:22:13.000+0100}, title = {Fr waves: A second fault-guided mode with implications for fault property studies}, url = {http://dx.doi.org/10.1029/96GL03424}, volume = 23, year = 1996 }