地震研究

南北地震带是中国强震频发区之一,分析该区域重力场时空变化趋势对理解强震机理、构造变形具有重要意义。引入二维水平梯度分析方法,基于2016年9月—2021年9月所获取的5期时变重力数据,计算南北地震带时变水平梯度值,结合研究区地震信息和地质构造资料,分析2017年以来研究区M_S≥5.0震中区域地震震前时变水平梯度与地震活动的时空分布特征。结果表明:研究区M_S≥5.3地震震中区域震前时变水平梯度特征与震级呈正相关; M_S≥6.0地震震中区域震前时变水平梯度高值带逐渐沿块体边界、大型断裂展布,极大值大于1.7 μGal/km,区域标准差大于0.4 μGal/km。

The North-South Seismic Belt is one of the regions where strong earthquakes occur frequently in China.Analyzing the temporal and spatial variation trend of the gravitational field on this belt is of great significance for understanding the mechanism of strong earthquakes and the tectonic deformation.In this paper,a two-dimensional horizontal gradient analysis method is introduced.Based on five periods of time-varying gravity data obtained from September 2016 to September 2021,the time-varying horizontal gradient values of the North-South Seismic Belt are calculated.Based on the records of the historical earthquakes(M_S≥5.0)and the geological structure in the study area,the temporal and spatial distribution characteristics of the pre-earthquake time-varying horizontal gradient and the historical earthquakes(M_S≥5.0)in the study area since 2017 are analyzed.The results indicate that the time-varying horizontal gradient before the M_S≥5.3 earthquakes is positively correlated with the magnitude of these earthquakes.Before the M_S≥6.0 earthquakes,the high-value zone of the time-varying horizontal gradient gradually extends along the block boundaries and the large faults.In addition,the maximum value can be greater than 1.7 μGal/km,and the regional standard deviation can be greater than 0.4 μGal/km.

引言
1 研究区概况及数据来源
2 二维水平梯度分析方法原理
3 地震发震特征分析
4 结论

图1 南北地震带历史地震和构造块体分布<br/>Fig.1 Historical earthquakes and tectonic blocksin the North-South Seismic Belt area

图1 南北地震带历史地震和构造块体分布
Fig.1 Historical earthquakes and tectonic blocksin the North-South Seismic Belt area

图2 水平梯度提取方法<br/>Fig.2 Extraction method for the horizontal gradient

图2 水平梯度提取方法
Fig.2 Extraction method for the horizontal gradient

表1 不同时间尺度的时变水平梯度均值及标准差<br/>Tab.1 Mean values and standard deviation of thetime-varying gradient in different time scales

表1 不同时间尺度的时变水平梯度均值及标准差
Tab.1 Mean values and standard deviation of thetime-varying gradient in different time scales

表2 南北地震带MS≥5.0地震震中区域时变水平梯度极大值及区域标准差<br/>Tab.2 Maximum value of the time-variable horizontal gradient and rigional deviation in the epicentral area(MS≥5.0)

表2 南北地震带MS≥5.0地震震中区域时变水平梯度极大值及区域标准差
Tab.2 Maximum value of the time-variable horizontal gradient and rigional deviation in the epicentral area(MS≥5.0)

图3 孕震区域时变水平梯度值特征统计<br/>Fig.3 Features of the time-varying horizontalgradient values in the seismogenic zone

图3 孕震区域时变水平梯度值特征统计
Fig.3 Features of the time-varying horizontalgradient values in the seismogenic zone

图4 2016年9月—2021年9月南北地震带中部地区时变水平梯度分布<br/>Fig.4 Distribution of the time-varying horizontal gradient in the central part of theNorth-South Seismic Belt from September 2016 to September 2021

图4 2016年9月—2021年9月南北地震带中部地区时变水平梯度分布
Fig.4 Distribution of the time-varying horizontal gradient in the central part of theNorth-South Seismic Belt from September 2016 to September 2021

图5 2017年9月—2021年9月南北地震带中部地区时变水平梯度分布(断裂同图 4)<br/>Fig.5 Distribution of the time-varying horizontal gradient in the central part of the North-South Seismic Belt from September 2017 to September 2021(faults are shown in Fig.4)

图5 2017年9月—2021年9月南北地震带中部地区时变水平梯度分布(断裂同图 4)
Fig.5 Distribution of the time-varying horizontal gradient in the central part of the North-South Seismic Belt from September 2017 to September 2021(faults are shown in Fig.4)

图6 2018年9月—2021年9月南北地震带中部地区时变水平梯度分布(断裂同图 4)<br/>Fig.6 Distribution of the time-varying horizontal gradient in the central part of the North-South Seismic Belt from September 2018 to September 2021(faults are shown in Fig.4)

图6 2018年9月—2021年9月南北地震带中部地区时变水平梯度分布(断裂同图 4)
Fig.6 Distribution of the time-varying horizontal gradient in the central part of the North-South Seismic Belt from September 2018 to September 2021(faults are shown in Fig.4)

图7 2019年9月—2021年9月南北地震带中部地区时变水平梯度分布(断裂同图 4)<br/>Fig.7 Time-varying horizontal gradient distribution in the central part of the North-South Seismic Belt from September 2019 to September 2021(faults are shown in Fig.4)

图7 2019年9月—2021年9月南北地震带中部地区时变水平梯度分布(断裂同图 4)
Fig.7 Time-varying horizontal gradient distribution in the central part of the North-South Seismic Belt from September 2019 to September 2021(faults are shown in Fig.4)

图8 2020年9月—2021年9月南北地震带中部地区时变水平梯度分布(断裂同图 4)<br/>Fig.8 Distribution of the time-varying horizontal gradient in the central part of the North-South Seismic Belt from September 2020 to September 2021(faults are shown in Fig.4)

图8 2020年9月—2021年9月南北地震带中部地区时变水平梯度分布(断裂同图 4)
Fig.8 Distribution of the time-varying horizontal gradient in the central part of the North-South Seismic Belt from September 2020 to September 2021(faults are shown in Fig.4)

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备注

引言

1 研究区概况及数据来源

2 二维水平梯度分析方法原理

3 地震发震特征分析

4 结论

期刊信息