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| Titel |
Frictional properties of sedimentary rocks and natural fault gouge from the Longmenshan Fault Zone, Sichuan, China |
| VerfasserIn |
Berend A. Verberne, Changrong He, Christopher J. Spiers |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250038655
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| Zusammenfassung |
| The Longmenshan Fault Zone (LFZ) in southwestern China slipped catastrophically during
the Great Wenchuan Earthquake of May 2008. In this contribution, we report friction
experiments performed on samples collected from the region of the LFZ hit by the event. The
materials tested consisted of simulated gouges prepared from intact clay-rich mudstone and
sandstone, a calcite limestone, plus a natural fault gouge from a trenched, surface
rupture cutting the mudstone and sandstone. The clay-rich samples, including the
natural gouge, were dominated by illite and quartz. In our experiments, we sheared
1-mm-thick gouge layers between saw-cut driver blocks, using a triaxial testing
machine at conditions corresponding to ~2 km depth in the LFZ. Temperature was
varied from 25 to 150Ë C and, to investigate the velocity dependence of friction,
we stepped the shear displacement rate between 1.22 and 0.122 μm/s. Our results
show that the natural gouge was more illite-rich and much weaker than the protolith
mudstone and sandstone, and showed a steady-state friction coefficient of ~0.4
compared with ~0.6 for the latter. The limestone gouge displayed values of 0.6-0.7.
All samples, except the limestone, showed stable, velocity-strengthening slip. The
limestone showed velocity-strengthening at 25-50Ë C, but quasi-static oscillations at
100-150Ë C along with velocity-weakening behavior at 150Ë C. We apply our
results to discuss the role of the sedimentary rocks studied during events such as the
Wenchuan earthquake, and argue that the clay-rich sediments of the region may have a
damping effect upon ruptures propagating from depth, whereas the limestone may
accelerate propagation, producing significant stress drops and enhancing seismic risks. |
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