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| Titel |
New evidence that the 1999 Mw=7.6 Chi-Chi earthquake is a characteristic earthquake: Deciphering long-term (30 ka) fault slip vectors on the northern Chelungpu fault from fold scarps on alluvial terraces |
| VerfasserIn |
Maryline Le Béon, John Suppe  , Manoj Jaiswal, Yue-Gau Chen, Michaela Ustaszewski |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094748
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| Publikation (Nr.) |
 EGU/EGU2014-10179.pdf |
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| Zusammenfassung |
| In convergent tectonic setting, fold scarps on alluvial terraces provide a quantitative long-term record of the amount of slip through an underlying fault bend since abandonment of the terraces. Cumulative slip can be computed in 3 independent ways, based on the terrace height in the hanging-wall relative to base level, the fold-scarp relief, and the width of the fold-scarp limb. We use these techniques to invert for fault-slip magnitude and azimuth from fold scarps on dated alluvial terraces in the hanging wall of the northern Chelungpu thrust, located at the piedmont of the Taiwan fold-and-thrust belt. Three main levels of alluvial terraces show progressive folding by kink-band migration in relation to the underlying fault geometry, forming a main N-S fold scarp up to ~193 m high and secondary E-W scarps. Based on scarp relief, the 3D deformation of the highest terrace T1, OSL-dated at ~30 ka, leads to 523 ± 81 m cumulative slip oriented N338° ± 6°, which is parallel to the 1999 Mw=7.6 Chi-Chi coseismic displacements in this area (N333° to N341°), but strongly different from the azimuth of interseismic deformation (N285°). In a similar direction, scarp reliefs on terraces T2 and T3, OSL-dated at ~22 ka and ~17 ka respectively, yield slip values of 432 ± 78 m and 271 ± 62 m, respectively. The slip and age results indicate a constant fault slip rate of 17.7 ± 2.2 mm/a along N338° ± 6°. Late Quaternary shortening rates observed at 4 sites along the fault vary in similar proportion to Chi-Chi coseismic displacements. Together with the colinearity of long-term and coseismic slip vectors at our study site, this suggests that Chi-Chi earthquake is a characteristic earthquake for the Chelungpu thrust with an average recurrence of ~440 years for the last ~30 ka. |
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