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Five Short Historical Earthquake Surface Ruptures near the Silk Road, Gansu Province, China

2010; Seismological Society of America; Volume: 100; Issue: 2 Linguagem: Inglês

10.1785/0120080282

1943-3573

Xiwei Xu, Robert S. Yeats, Ge Yu,

High-pressure geophysics and materials

Five historical earthquakes (M ≥7) have occurred along the Hexi Corridor at the northeastern margin of the Tibetan Plateau since A.D. 180. These are the A.D. 180 Gaotai earthquake (M 7.5), the 1609 Hongyazi earthquake (M 7.25), the 1927 Gulang earthquake (M 8.0), the 1932 Changma earthquake (M 7.6), and the 1954 Shandan earthquake (M 7.3). They are predominantly reverse slip, except for the 1932 Changma and the 1954 Shandan earthquakes. The Changma earthquake is char- acterized by left-lateral faulting with a reverse component, while the Shandan earth- quake by right-lateral faulting with a normal component. Fieldinvestigationsindicatethatthelengthofthesurface-rupturezoneisonly28km for the A.D. 180 earthquake, 11 km for the 1609 earthquake, 23 km for the 1927 earth- quake, and 5.1 km for the 1954 earthquake, much shorter than that predicted using an empirical equation between moment magnitude (Mw), surface-rupture length (SRL), coseismic displacement (D), maximum displacement (MD), average displacement (AD), and mode value combined displacement statistic (MVCDS): Mw � 5:91� 0:609logSRL × Dfor strike-slip faults, Mw � 5:81 � 0:653logSRL × Dfor reverse faults, and Mw � 6:93 � 0:82logAD × MVCDSfor all faults. This may be common for reverse faulting earthquakes worldwide and suggests that trying to estimate magnitudes of past earthquakes from one type of even the most recent surface-rupture data is unreliable and the empirical equations between magnitude, coseismic slip, and surface-rupture length should be applied with caution to seismic hazard assessment on active thrust faults.