摘要
1927年古浪发生8级大地震,此次地震给古浪及邻近地区造成了轻重不等的破坏。对这次地震的发震构造,前人的研究结果存在较大分歧。本研究根据成丛小震发生在大震断层面附近的原则及参考前人对该地震发震构造的认识,采用1985年到2012年发生在地震破裂区的精定位地震目录,选定了2个长条状研究区域,将模拟退火算法和高斯-牛顿算法结合,利用小震密集程度求解主震断层面的走向与倾角。在此基础上考虑区域构造应力参数,给出了已求得的断层面上的滑动角。然后结合已有的深部构造研究结果以及地表考察结果,简单讨论了此次地震的孕震环境和发震机制。文中反演到的断层1位于此次地震等震线的最高烈度(Ⅺ度)圈内,表明反演到的震源断层可能就是控制此次地震的发震构造。另外,首次发现在主干断裂中南部有1个小震成丛区,也能反演出1个断层,这可能是地震时震区整体发生了逆时针旋转而在主干断裂之上新发育的张性地震断层。
The Gulang M8.0 great earthquake occurred in 1927,many places in Gulang and adjacent areas had suffered destruction in various degrees. So far,divergences exist in the former studies on its seismogenic structure. It is known that clustered small earthquakes often occur in vicinities of fault plane of large earthquake. In this study,the precisely relocated earthquakes which occurred near the earthquake rupture zone between 1985 and 2012 are used,and two strip-shaped zones of clustered small earthquakes are chosen according to the previous studies of the causative structure of this earthquake. Based on the simulated annealing and Gauss-Newtonian nonlinear inversion algorithms,we obtained fault plane parameters of the earthquake such as strike,dip,and location using data of densely concentrated small events. On this condition,rake angles of the fault plane are further inferred from regional tectonic stress parameter. Then we discussed briefly the seismogenic environment and causal mechanism of the earthquake,combined with the results of deep tectonics and surface investigations. The focal fault we inverted locates within the meizoseismal area（ intensity Ⅺ）of the Gulang M8.0 in 1927,suggesting that the focal fault obtained by inversion is possibly the causative structure of this earthquake. Besides,we found a clustered zone of small earthquakes near the south-central part of the main fault,and a fault plane could be derived from them,which we think might be a tensional seismic fault developed on the main fault when the whole earthquake-hit region rotated counterclockwise during the big earthquake.
出处
《地震地质》
EI
CSCD
北大核心
2015年第3期818-828,共11页
Seismology and Geology
基金
中国地震局兰州地震研究所地震科技发展基金(2012Y03)
甘肃省青年科技基金计划(145RJYA316)
中国地震科学台阵探测项目(A34)共同资助
关键词
小震丛集
古浪地震
断层面解
发震构造
small earthquake clustering, the Gulang earthquake, fault plane solution, causative structures
