怒江断裂现今错动速率与地震危险性

PRESENT-DAY SLIP RATES AND POTENTIAL EARTHQUAKE RISKS ALONG THE NUJIANG FAULT

针对怒江水电开发问题的争论之一:怒江断裂带的现今活动性及其地震危险性。通过分析怒江地区最新GPS观测数据,采用剖面投影方法估算得到怒江断裂亚碧罗—六库段、六库—赛格段和赛格以南段的右旋走滑速率分别为(4.7±0.8)mm/a、(6.4±1.1)mm/a和(4.3±0.3)mm/a,拉张速率分别为(3.9±0.6)mm/a、(5.6±1.1)mm/a和(4.5±0.3)mm/a。结合怒江地区的地震资料,分别通过弹性能累积量和同震位错量与震级间的统计关系进行地震危险性分析,认为上述断裂段分别具有发生6.4级、6.5级和6.4级地震的危险性,且不排除发生更大震级地震的可能。由于怒江断裂大体沿怒江展布,为保证水坝安全,其选址和抗震设防强度要求应当考虑以上断层活动性和地震危险性评估结果。

Disputes arise during the hydroelectric development along the Nujiang River, among which we focus on the present activity of the Nujiang Fault and its potential earthquake risks. Using velocity profiles derived from an updated GPS dataset in the Nujiang region, slip rates are estimated as 4.7± 0.8, 6.4± 1.1, and （ 4.3±0.3 ） mm/a right-laterally and 3.9± 0.6, 5.6± 1.1, and （ 4.5±0.3 ） mm/a extensionally along the Yabiluo-Liuku, Liuku-Saige, and south Saige segments of the Nujiang Fault, respectively. According to the relationship between accumulated amount of elastic energy and fault slip rate and that between earthquake magnitude and rupture displacement, above estimates and earthquake catalog suggest potentials of earthquakes with magnitudes 6.4, 6.5, and 6.4 or even larger on the Yabiluo-Liuku, Liuku-Saige, south Saige segments, respectively. Provided that the surface trace of the Nujiang Fault is distributed generally along the Nujiang River, our estimates of fault slip rates and seismic potentials should be taken into account in dam siting and determining requirements of seismic fortification for safety.