汶川、芦山和康定地震造成的鲜水河断裂带库仑应力变化及对地震危险性的影响

通过估算汶川、芦山和康定地震造成的鲜水河断裂带库仑应力变化,并与其长期构造应力加载速率进行比较,分析3次地震对鲜水河断裂带未来地震危险性的影响。结果显示,汶川和芦山地震对康定地震的发生分别起到促进和推迟作用;3次地震造成的总应力扰动主要来自汶川和康定地震。在线性应力加载条件下,当断层面等效摩擦系数μ′=0时,3次地震的相继发生会使鲜水河断裂带八美至磨西(除康定地震破裂带外)的地震提前0~5a,其余地区推迟0~4a;当μ′=0.4时,3次地震会使道孚至猪腰子海子(康定地震破裂带除外)的地震提前0~6a,其余地区推迟0~2a。考察了不同流变学结构对计算结果的影响,发现下地壳上地幔粘滞性系数越低,介质粘滞性响应造成的库仑应力变化越大,沿走向的变化越剧烈,其贡献基本与同震相当,对地震提前/延迟时间估计结果的影响最大可达3a。

Coulomb Stress Changes Along the Xianshuihe Fault Induced by the Wenchuan,Lushan and Kangding Earthquakes and Their Impacts on Seismic Potentials

Coulomb stress changes along the Xianshuihe fault induced by the Wenchuan, Lushan and Kangding earthquakes are calculated and compared with long term tectonic loading rates in order to assess seismic potential change on the fault due to these earthquakes. The results show that the Kangding earthquake was advanced and delayed by the Wenchuan and Lushan earthquakes, respectively.Most of the Coulomb stress changes along the Xianshuihe fault are due to the Wenchuan and Kangding earthquakes.Under a linear stress loading assumption, advance/delay times of earthquake recurrence are calculated along the fault.In the case assuming μ′=0, the earthquake recurring times could be advanced by approximately 0-5 years at locations between Bamei and Moxi〖JP2〗（except the rupture zone of the Kangding earthquake), and delayed by 0-4 years at the other regions, respectively.If μ′=0.4, the advance times of earthquake recurrence are estimated as 0-6 years in the range between Daofu and Zhuyaozihaizi, and the delay times are calculated to be 0-2 〖JP3〗years out of the range.As our knowledge is so limited about the rheological structures on both sides of the Xianshuihe fault, the impact of its variation on the results is also investigated.Our research shows that the lower the viscosities of the lower crust and the upper mantle, the larger the Coulomb stress change due to viscous relaxation would be, and the more rapidly it changes along fault strike.Furthermore, the contribution of the viscous relaxation is comparable to that of coseismic rupture, resulting in advance/delay times of earthquake recurrence of up to 3 years.