Distribution of seismic intensities of the November 6, 1988, Lancang-Gengma earthquakes and their surface ruptures in Yunnan Province, China
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On November 6, 1988, two earthquakes with magnitude>7 occurred on the Lancang-Gengma fault zone in south-west China. The extensive destruction and loss of lives resulted mainly from widespread collapse of unreinforced masonry and mud brick structures; the maximum preliminary intensity of the Lancang earthquakes was IX on the Chinese scale, which is similar to the Modified Mercall scale, and the highest preliminary intensity of the Gengma earthquake was probably X.
The surface manifestation of tectonic activity of the Lancang earthquake was the occurrence of the earthquake-related extensional ground cracks and small fault scarps in the epicentral region. The cracks with small fault scarps occurred mainly in four relatively continuous north-northwest-trending linear zones that ranged from a few hundred meters to 6 km in length. The area within which the cracks and small scarps occurred is 35 km long by 3 km wide. The maximum net throw and the dextral horizontal offset were 1.5m and 1.4m, respectively.
Clear evidence of new surface faulting caused by the Gengma earthquake includes a series of relatively continuous north-northwest-trending linear ground crack zones and a 5 km long section of fault scarps. The total length of the surface rupture zones of the Gengma earthquakes is about 24 km, with 3.5m maximum net throw and 3m maximum right-lateral slip.
Both earthquakes were associated with surface faulting showing a combination of normal and right lateral motion. The distribution of seismic intensities and surface rupture characteristics of these two earthquakes are discussed in this paper.
Key wordsLancang-Gengma earthquakes Yunnan Province seismic intensity surface ruptures fault scarps
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- Aki, K., 1978. Characterization of barriers on an earthquake fault.J. Geophys. Res.,84, 6140–6148.Google Scholar
- Bruhn, R. L., Gibber, P. R. and Parry, W. T., 1987. Rupture characteristics of normal faults, an example from the Wasatch fault zone, Utah.Continental Extensional Tectonics. editted by Coward,M. P. Dewey, T. F. and Hancock, P. L., Geol. Soc. Publ. No. 28, 337–353.Google Scholar
- Philip, H. and Meghraoui, M., 1984. Structural analysis and interpretation of the surface deformations of the E1 Asnam earthquake of October 10, 1980.Tectonics,2, No. 1, 17–47.Google Scholar
- Research Group on Lancang-Gengma earthquake area, Inst. Geol., SSB, 1989. A preliminary report on the results of integrated investigation of Lancang-Gengma earthquake area.Seismology and Geology,11, 1, 135–136(in Chinese with English abstract).Google Scholar