In the northern segment of the North-South seismic zone there are unbroken active faults, on which no Ms≥7. 0 earthquakes have occurred for a long time. These faults can be identified by jointly investigating active tectonics and faulting pattern of strong earthquakes in this region. A viscoelastic stress model is used to estimate the potential earthquake risk on these unbroken active faults. This model could aptly describe transient coseismic elastic response and short-term postseismic exponential strain relaxation. Based on the evolution model of Coulomb failure stress, the spatial pattern of seismicity following the Dieterich rate- and state-dependent constitutive law was calculated. The result of earthquake damage probability estimation indicates that the regions having the risk level from high to low are sequentially the Ruoergai-Jiuzhaigou region of east Kunlun fault, middle and southern Liupanshan fault, Tongxin region of middle and southern Xiangshan-Tianjingshan fault, Tianzhu-Dajing region, middle and west segments of western Qinling Mountain fault and east segment of western Qinling Mountain fault.%综合活动构造与重要活动断裂带的历史及现今强震震源区或破裂分布等资料,南北地震带北段存在长期缺少Ms≥7.0地震的破裂空段.为了考察这些空段的地震危险性,首先采用Burgers体黏弹介质模型,计算周围有记载以来的历史强震在空段引起的库仑应力动态演化；其次结合背景地震发生率,采用Dieterich模型分析历史强震对空段地震活动的影响,讨论了空段所在区域的地震发生概率.结果显示,南北地震带北段强震破裂空段的地震危险性程度自高到低依次是:东昆仑活动断裂带东段的若尔盖—九寨沟段、六盘山断裂带中南段空段、香山—天景山段裂中南段同心空段、天祝—大靖空段、西秦岭北缘断裂带中西段、西秦岭北缘断裂带东段.该结果可为南北地震带北段的地震危险性估计提供参考.
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