The Xiaojiang fault is an active boundary fault on the southeastern Tibetan Plateau. Historical earthquake records indicate that the Xiaojiang fault has been struck by at least four multi-segment rupturing events. Why and where the Xiaojiang fault is prone to multi-segment earthquakes need to be well studied. To investigate the multi-segment seismic hazard of the Xiaojiang fault, we divide the Xiaojiang fault, the nearby Qujiang fault, and Jianshui fault, into 34 fault segments according to the new geological mapping results. We build four possible multi-segment rupture combination models, and then analyze the geological studies to select appropriate fault slip rates. We use the selected fault slip rates and the Magnitude-Frequency relationship to model the future seismicity rates for these rupture combinations. We find that the multi-segment rupture combination model developed from the historical rupture events that did not rupture through the step-over with a 12-km-width and the adjoining segments with strike difference ≥28°, showing the effectiveness of consuming the strain accumulation on the fault in our calculation. Finally, we calculate the Peak Ground Acceleration (PGA) values from the compatible multi-segment rupture combination model. Our results show that the PGA value is relatively lower around the middle section of the Xiaojiang fault, which agrees with the multi-segment rupturing tendency from historical seismicity and paleo-earthquakes studies. The high probabilities of the multi-segment rupturing for the Xiaojiang fault are determined by the fault segment distribution based on the new geological mapping results.

小江断裂是青藏高原东南部的一条活动边界断裂。历史地震记录表明，小江断层至少受到过四次多段破裂事件的撞击。小江断层为什么会发生多段地震，在什么地方容易发生多段地震有待深入研究。为研究小江断裂的多段地震危险性，根据新的地质填图结果，将小江断裂、附近的曲江断裂和建水断裂划分为34个断层段。我们建立了四种可能的多段破裂组合模型，然后分析地质研究以选择合适的断层滑动率。我们使用选定的断层滑动率和震级-频率关系来模拟这些破裂组合的未来地震活动率。我们发现多段破裂组合模型是由历史破裂事件发展而来的，这些事件没有通过12公里宽的跨步和走向差异≥28°的相邻段，显示了消耗应变的有效性在我们的计算中累积在故障上。最后，我们根据兼容的多段破裂组合模型计算峰值地面加速度 (PGA) 值。结果表明，小江断裂中段附近的PGA值相对较低，这与历史地震和古地震研究的多段破裂趋势一致。小江断裂多段破裂的高概率是由基于新地质填图结果的断裂段分布决定的。