Understanding fault rupture during major earthquakes, and the resulting ground motions, is limited by our observational capabilities. Observations of very large amplitude seismic waves, especially direct measurements of displacement, would make a significant improvement in constraining the size of dynamic strains that trigger remote seismicity and in revealing details of the source rupture process. For example, accelerometers capture the details of strong ground shaking near the source, but it is difficult to convert the acceleration measurements unambiguously to displacement which is required for determining the source time history. Broad-band seismometers are more sensitive, and have better resolution of ground motion, but frequently clip, saturate, or become non-linear even at great distances from a large earthquake. Interferometric Synthetic Aperture Radar (InSAR) observations can produce spatially rich images of some components of surface displacement surrounding a rupture, but InSAR fails in many regions and has no temporal resolution to resolve dynamic phenomena. Global Positioning System (GPS) geodetic measurements have been important for resolving static offsets, but are usually sampled at such a low rate that resolving details of the rupture process was not frequently attempted.

Our group has worked on GPS seismic signals for the Denali, Tokachi-Oki, Parkfield, and San Simeon Earthquakes. Our model for the Tokachi-Oki rupture can be seen here. Please click on the publications listed below for more information about the other earthquakes.

Our work is funded by NFS (EAR-0337206 and EAR-0538116) and the USGS NEHRP (Tokachi-Oki earthquake). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of NSF.

Please send questions and comments to kristinem.larson at gmail.com

Archived Results at IRIS:

• Denali and Tokachi-Oki

Publications:

• Larson, K., P. Bodin, and J. Gomberg, Using 1 Hz GPS Data to Measure Deformations Caused by the Denali Fault Earthquake, Science, Vol. 300, 1421-1424, 2003. reprint (pdf).
  Online supplement can be downloaded directly from Science

• Gomberg, J., P. Bodin, K. Larson, H. Dragert, Earthquakes nucleated by transient deformations - a fundamental process evident in observations surrounding the M7.9 Denali Fault Alaska Earthquake, Nature, 427, 621 - 624, (12 Feb 2004) (pdf).

• Ji, C., K. M. Larson, Y. Tan, K. Hudnut and K. Choi, Slip history of the 2003 San Simeon Earthquake constrained by combining 1-Hz GPS, strong motion, and teleseismic data, Geophys. Res. Lett., Vol. 31, No.17, L17608, 10.1029/2004GL020448, 2004, (pdf).

• Miyazaki, S., K. Larson, K. Choi, K. Hikima, K. Koketsu, P. Bodin, J. Haase, G. Emore, and A. Yamagiwa, Modeling the rupture process of the 2003 Tokachi-Oki earthquake using 1-Hz GPS data, Geophys. Res. Lett., Vol.31,No.21,L21603, 2004, (pdf).

• Choi, K., A. Bilich, K. Larson, and P. Axelrad, Modified sidereal filtering: Implications for high-rate GPS positioning Geophys. Res. Lett., Vol. 31, No.22, L22608, 2004, (pdf).

• Agnew, D. C. and K. M. Larson, Finding the Repeat Times of the GPS Constellation, GPS Solutions, (pdf), 2006.

• Emore, G., J. Haase, K. Choi, K. M. Larson, and A. Yamagiwa, Recovering absolute seismic displacements through combined use of 1-Hz GPS and strong motion accelerometers, BSSA, Vol 97:2, 357-378, 2007 (pdf).

• Larson, K., A. Bilich, and P. Axelrad, Improving the precision of high-rate GPS, J. Geophys. Res., 112, B05422, doi:10.1029/2006JB004367, 2007 (pdf)

• Bilich, A., J. Cassidy, and K. M. Larson, GPS Seismology: Application to the 2002 Mw=7.9 Denali Fault Earthquake, BSSA, April 2008; v. 98; no. 2; p. 593-606; doi: 10.1785/0120070096, (pdf).

• Larson, K., GPS Seismology, J. Geodesy, special issue for the IGS, Vol. 83 (3) (2009), 227-233, 2009 (pdf)

Background Information on High-Rate GPS