RESEARCH ON ACTIVITY OF ZHANGJIAKOU-BOHAI FAULT ZONE BASED ON GPS OBSERVATIONS

doi:10.3969/j.issn.0253-4967.2020.01.007

Abstract

Abstract:

The northwestern section of the Zhangjiakou-Bohai fault zone starts in the west of Zhangjiakou, extending southeast through Huailai, Shunyi and Tianjin and entering into the Bohai Sea, with a width up to several tens of kilometers, narrow in the west and wide in the east. The Neogene-Quaternary has extended in the northwest and southeast direction, forming a large regional active structure. There are many earthquakes of magnitude 7 or above in the history on the Zhangjiakou-Bohai fault zone and it is also a strong earthquake activity zone in eastern China. Therefore, the modern tectonic activities of this fault zone have an important impact on regional seismic hazard, and are of great significance for earthquake prediction and disaster reduction.
In this paper, using the mobile GPS station observation data of 1999, 2007, 2009, 2011, 2013 and 2015, and with the rigid-linear elastic block motion model equation proposed by LI Yan-xing, the horizontal deformation rate and strain rate of the Zhangjiakou-Bohai fault zone of the five adjacent periods of 1999—2007, 2007—2009, 2009—2011, 2011—2013 and 2013—2015 were calculated, the tectonic activity characteristics and evolution of the fault zone were studied. The results show that in the five periods, the average deformation rate of the Zhangjiakou-Bohai fault zone is 1.74mm/a, the left-lateral strike-slip rate is 1.59mm/a, and the compression rate is -0.59mm/a. The Zhangjiakou-Bohai fault zone is characterized by left-lateral strike-slip and compression on the whole, and the left-lateral strike-slip rate is greater than the compression rate at each period. The strike-slip rate is significantly greater than the compression rate, indicating that the activity of Zhangjiakou-Bohai fault zone is dominated by left-lateral strike-slip faulting with compression. The minimum principal strain rate of the Zhangjiakou-Bohai fault zone in the five periods varies from -12.06×10^-9/a to -4.62×10^-9/a, and the average minimum principal strain axis direction is N63.9°E, with little change in direction. The maximum principal strain rate varies from 1.55×10^-9/a to 5.99×10^-9/a, and the average maximum principal strain axis direction is N333.9°W, the direction does not change much. The strike of the Zhangjiakou-Bohai fault zone is NWW(the overall strike is calculated by N300°W), and the normal strain rate of the fault zone is -5.87×10^-9/a(being compressional), and the shear strain rate is 12.70×10^-9/a. The shear strain rate on the fault zone is about twice the value of the normal strain rate, and the shear strain rate of the fault zone is greater than the normal strain rate, which indicates the shear stress of the 5 periods of 1999—2007, 2007—2009, 2009—2011, 2011—2013 and 2013—2015 is relatively significant, suggesting that the fault plain is dominated by left-lateral shear stress. This suggests that the Japan 3·11 earthquake has little effect on the deformation strain of the Zhangjiakou-Bohai fault zone, and it does not change the nature of activity of the fault zone. The tectonic activity is still inheriting. Since the tectonic activity of the Zhangjiakou-Bohai fault zone has gradually decreased after the Japan 3·11 earthquake, the deformation strain evolution trend has gradually returned to a unified consistent state. Therefore, the deformation strain state of the Zhangjiakou-Bohai fault zone does not have the condition for strong earthquakes.

Key words: GPS horizontal deformation, Zhangjiakou-Bohai fault zone, left-lateral strike-slip rate, compression rate, normal strain rate, shear strain rate

摘要：

文中基于1999年、 2007年、 2009年、 2011年、 2013年以及2015年6期GPS区域站观测资料, 计算得到了5个相邻时段中张家口-渤海断裂带的水平形变速率和应变率, 据此研究了该断裂带的活动性演化特征。结果表明, 在5个时段中, 张家口-渤海断裂带的总体形变速率平均为1.74mm/a, 左旋走滑速率平均为1.59mm/a, 压缩速率平均为-0.59mm/a。张家口-渤海断裂带各时段的左旋走滑速率均大于压缩速率, 说明其活动性以左旋走滑活动为主, 兼有压缩运动。在5个时段中最小主应变率均小于0, 为压性, 最大主应变率>0, 为张性。张家口-渤海断裂带的主压应力方向均为NEE-SWW向, 主张应力方向NNW-SSE向; 正应变率均为负数, 为压性; 断裂带的剪应变率值相对于正应变率较大, 表明剪应力较强, 各时段均以左旋剪切应力作用为主。张家口-渤海断裂带的构造活动具有继承性, 在日本3·11大地震后, 其构造活动性呈现逐步减小的趋势。

关键词: GPS水平形变, 张家口-渤海断裂带, 左旋走滑速率, 压缩速率, 正应变率, 剪应变率

CLC Number:

P315.2

CHEN Fu-chao, GUO Liang-qian, ZHENG Zhi-jiang. RESEARCH ON ACTIVITY OF ZHANGJIAKOU-BOHAI FAULT ZONE BASED ON GPS OBSERVATIONS[J]. SEISMOLOGY AND GEOLOGY, 2020, 42(1): 95-108.

陈阜超, 郭良迁, 郑智江. 基于GPS观测的张家口-渤海断裂带活动性[J]. 地震地质, 2020, 42(1): 95-108.

Figures/Tables 13

Fig. 1 Distribution map of GPS stations in the Zhangjiakou-Bohai fault zone.

Fig. 2 Comparison of movement rates of GPS stations before and after model fitting.

Fig. 3 Deformation rate of Zhangjiakou-Bohai fault zone during 1999—2007.

Fig. 4 Deformation rate of Zhangjiakou-Bohai fault zone during 2007—2009.

Fig. 5 Deformation rate of Zhangjiakou-Bohai fault zone during 2009—2011.

Fig. 6 Deformation rate of Zhangjiakou-Bohai fault zone during 2011—2013.

Fig. 7 Deformation rate of Zhangjiakou-Bohai fault zone during 2013—2015.

Table1 Rate and direction of each time period

年份	1999—2007	2007—2009	2009—2011	2011—2013	2013—2015
平均位移方向/(°)	274	268	287	281	272
方向变化/(°)	286~263	292~268	321~256	247~330	268~278
位移速率/mm·a^-1	2.0	1.36	2.23	1.47	0.76
走滑速率/mm·a^-1	1.82	1.16	2.18	1.39	0.67
压缩速率/mm·a^-1	-0.88	-0.72	-0.50	-0.48	-0.35

Fig. 8 Principal strain rate of Zhangjiakou-Bohai fault zone during 1999—2007.

Fig. 9 Principal strain rate of Zhangjiakou-Bohai fault zone during 2007—2009.

Fig. 10 Principal strain rate of Zhangjiakou-Bohai fault zone during 2009—2011.

Fig. 11 Principal strain rate of Zhangjiakou-Bohai fault zone during 2011—2013.

Fig. 12 Principal strain rate of Zhangjiakou-Bohai fault zone during 2013—2015.

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