南北地震带垂直形变速率梯度与强震活动研究

Velocity Gradient of Vertical Deformation and Strong Earthquake Activity on the North—South Seismic Belt

垂直形变梯度能够有效反映区域构造运动的垂直差异变化程度。我们利用长时间段的水准资料结合GPS资料计算垂直形变梯度值,计算结果显示垂直形变速率梯度的空间分布与构造分布具有显著的相关性,南北地震带垂直形变速率梯度异常最显著区域在鲜水河断裂带、龙门山断裂带和小江—则木河断裂带附近,其次是青藏高原东北缘地区的庄浪河断裂带与冷龙岭断裂带交会区域,2016年门源6.4级地震就发生在这一异常区域内,但是从垂直形变速率梯度的高梯度区域分布来看,在天祝至景泰一带也有发生强震的背景。三大断裂交会区域是整个南北地震带构造活动最为强烈的区域,应该注意该地区未来强震发生的危险性。

Vertical deformation gradient can effectively reflect the rate of vertical change in the unit distance, and vertical deformation velocity gradient can reflect the strength of the earth＇s crust tectonic activities. In this paper, we use long period leveling data combined with GPS data to calculate vertical deformation gradients. Leveling and GPS are two different means of monitoring, but the result is approximately the same in vertical deformation gradient. The calculation results show that the relevance of the spatial distribution of vertical deformation velocity gradient and tectonic distribution is obvious. The most significant gradient anomalies in the North--South Seismic Belt appear on the Xianshuihe fault, Longmenshan fault and Xiaojiang--Zemuhe fault, the second gradient anomalies in the northeastern Tibet plateau appear on the Zhuanglanghe fault and Lenglongling fault, and the 2016 Menyuan M6.4 earthquake occurred in this abnormal area. From the high gradient distribution of vertical deformation, there is also possibility of earthquake around Tianzhu and Jingtai. The tectonic activities of North--South Seismic Belt has become stronger especially in the intersection area of the three major fault zone.