摘要
川滇交界东段NE向昭通、莲峰断裂带的研究程度较低.为了了解该断裂带是否存在发生强震/大地震的危险背景,我们基于区域活动构造与动力学、重新定位的小震分布和震源机制解、历史地震破裂区、GPS形变场、现代地震活动及其参数图像等多学科的信息进行综合研究.结果表明:昭通、莲峰断裂带是川滇-华南活动块体/地块边界带的一部分,也是活动及变形的大凉山次级块体与相对稳定的华南地块之间的边界带;结构上表现为2个平行展布、朝南东推覆的断裂带,现今运动为带有显著逆冲分量的右旋走滑性质.沿昭通断裂带无大地震的时间至少为1700余年,目前存在地震空区.GPS变形图像反映昭通、莲峰断裂带已不同程度闭锁.另外,昭通断裂带的鲁甸附近以及莲峰断裂带的南段分别存在异常低b值区或高应力区.已由低b值区和小震空白区识别出昭通断裂带上的鲁甸—彝良之间存在高应力闭锁段,并估计出其潜在地震的最大矩震级为MW7.4.本研究因此认为昭通断裂带存在发生强震/大地震的中-长期危险背景,而莲峰断裂带的危险性还需进一步研究.
The NE-trending Zhaotong and Lianfeng fault zones of the eastern Sichuan-Yunnan border region are poorly studied on earthquake issues. To know whether the two fault zones have seismic potential for strong and major earthquakes, we make a comprehensive study by integrating multidisciplinary data of active tectonics and regional dynamics, distribution of relocated small earthquakes and focal mechanism solutions, historical earthquake rupture-areas, GPS deformation field, modern seismicity and its parameter patterns, etc. Our study shows that the Zhaotong and Lianfeng fault zones are a part of the boundary separating the Siehuan-Yunnan block and the South China block, and also the margin between the active and deformed secondaryfaulted block of Daliangshan and the relatively stable South China block. Structurally, the fault zones appear as two parallel and southeastward thrusting fault zones with the currently right- lateral strike slip faulting along with significant thrusting components. Along the Zhaotong fault zone the time without major earthquakes is proved to have been over 1700 years at least, and a seismic gap exists there. The GPS deformation patterns suggest that the Zhaotong and Lianfeng fault zones have locked in different degrees. Also, several areas of low b-values or high stress exist on the Zhaotong fault zone near Ludian and on the southern segment of the Lianfeng fault zone. A locked or highly stressed fault segment of the Zhaotong fault zone between Ludian and Yiliang has been identified from low b-values and lack of current small earthquakes, and the moment magnitude for a maximum potential event on this fault segment is estimated to be about Mw7.4. We therefore conclude that mid- to long-term seismic potential for strong or major earthquakes exists on the Zhaotong fault zone. But, the seismic potential of the Lianfeng fault zone still needs to be studied further.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第10期3361-3372,共12页
Chinese Journal of Geophysics
基金
国家科技支撑计划项目课题(2012BAK19B01-01)专题
中国地震局M7工作专项(2013)资助
