HR: 17:00h
AN: G12A-05    [PDF]
TI: Measuring Fault Slip - Why and How?
AU: * Hudnut, K W
EM: hudnut@usgs.gov
AF: U. S. Geological Survey, 525 S. Wilson Ave., Pasadena, CA 91106
AU: Aagaard, B
AF: U. S. Geological Survey, 525 S. Wilson Ave., Pasadena, CA 91106
AU: Anderson, G
AF: U. S. Geological Survey, 525 S. Wilson Ave., Pasadena, CA 91106
AU: Aspiotes, A
AF: U. S. Geological Survey, 525 S. Wilson Ave., Pasadena, CA 91106
AU: Bevis, M
AF: Ohio State University, 2070 Neil Ave., Columbus, OH 43210
AU: Borsa, A
AF: IGPP - U. C. San Diego, 9500 Gilman Dr., La Jolla, CA 92093
AU: Heaton, T
AF: Caltech, 1201 E. California Blvd., Pasadena, CA 91125
AU: King, N
AF: U. S. Geological Survey, 525 S. Wilson Ave., Pasadena, CA 91106
AU: Minster, J
AF: IGPP - U. C. San Diego, 9500 Gilman Dr., La Jolla, CA 92093
AU: Stark, K
AF: U. S. Geological Survey, 525 S. Wilson Ave., Pasadena, CA 91106
AB: To improve our understanding of earthquake physics, we must make observations of parameters that determine friction on the fault surface during rupture. Observables may include, for example, 3D point trajectories to fully record near-field dynamic phenomena such as slip pulses, as well as details of slip variation along strike. We have devised and tested new methods for observing these quantities in nature. First, we observed the details of topography along the 1999 Hector Mine surface rupture using Airborne Laser Swath Mapping. This allowed us to estimate slip variation along-strike of the fault, in some places, with higher spatial resolution than has ever before been possible. The results are, however, complex due to ground surface irregularity and pre-existing topographic features. Evidently, slip variations along strike are greater than previously recognized, implying extreme slip heterogeneity. We provide a simple explanation for how such rapid slip variations could provide the source for high-frequency seismically radiated energy, at least in the near field. Second, we have developed the concept for, and built a working prototype of, a GPS Fault Slip Sensor spanning the San Andreas fault. In addition to augmenting seismic early warning systems, such instrumentation could also provide unique records of near-field ground motions. Inertial sensors such as seismic instruments are not able to differ between a tilt and an acceleration, whereas GPS measurements can differentiate these, and can be made with respect to an absolute frame of reference. Other practical limitations exist, however, in both kinds of instrumentation and we will describe how they may best be integrated into a system that will achieve both the scientific observational objectives and support earthquake early warning.
DE: 1206 Crustal movements--interplate (8155)
DE: 1242 Seismic deformations (7205)
DE: 5104 Fracture and flow
DE: 7205 Continental crust (1242)
DE: 7209 Earthquake dynamics and mechanics
SC: Geodesy [G]
MN: 2003 Fall Meeting