On May 29, 1976 (at Beijing time 20h23m and 22h00m) two strong earthquakes of magnitude 7.5 and 7.6 respectively occurred in Long Ling of Yunnan province. The epicentral area (Intensity Ⅷ-Ⅸ) lies in a middle mountain region with granite outcrops. The widespread rock-fall from the weathered granite crust forms the chief hazard caused by the strong shocks.This paper emphatically Analyses the geological conditions causing earthquake rock-fall which occurred mostly on the two steeper flanks of a narrow ridge separating erosional valleys and in granite bodies of the Yen’shanian orogeny-, especially in those of the first and second stages of intrusion (γ53(1),γ53(2)). Comparing with the two subsequent intrusive stages (γ53(3), γ53(4)) the first and the second stages are characterizied by less homogeneous texture and relatively higher content of easily weathered minerals in mineral constituents. In addition, under similar geologic and geomorphologic conditions the earthquake rock-fall largely happened on such slopes where vegetation (particularly the deeply rooted one) is lacking.Finally, it is suggested that the Long Ling earthquake is similar in ground failure to those shocks occurring in mountain area in recent years, predominating in seismogenic gravitative failure. The earthquake rock-fall of such a large scale, however, has never been known before.
. 1977, 地震剥落——花岗岩地区的一种典型震害. 地质科学, 12(4): 394-398.
. A TYPICAL EARTHQUAKE HAZARD IN GRANITE AREA ——EARTHQUAKE ROCK-FALL[J]. Chinese Journal of Geology, 1977, 12(4): 394-398.