Introduction
| 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. |
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This project specifically exploits high-rate GPS measurements to improve our understanding of the rupture process of the Mw 7.9 Denali Fault earthquake of 3 November 2002. The first phase of this project assesses the technical issues relating to the reliability and utility of these new GPS observations. In the second phase, the resulting data are used to complement existing seismic data: (1) to better understand the ground motions from the Denali earthquake that triggered earthquakes remotely, and (2) to use the surface waves at far-regional distances to validate rupture models of the Denali Fault earthquake mainshock.
Some New Results:
See a Rupture Animation our GRL paper
The model results (in red) are courtesy of Chen Ji (Caltech). The observations are from IISC (Bangalore, India).
If the earthquake happened at T=0, is that a precursor?
This research is funded by NSF and the USGS NEHRP program.
