地震研究

基于2019—2023年的流动重力观测资料,使用经典平差获得各测期测点重力值,得到研究区不同时间尺度的重力场变化结果; 使用GAMMA软件对InSAR同震观测数据进行干涉处理,获取2021年青海玛多M_S7.4地震的同震形变场。结果显示:玛多M_S7.4地震震前研究区异常变化主要集中在震中附近,以负变化为主; 地震前后1年期的重力场变化形成了“四象限”的分布特征; 震后研究区重力场发生大范围的反向变化,但随着震后调整,震中区域东部的重力场变化量较西部更大,与双断层滑动模型给出的滑动量分布结果一致。玛多地震在LOS向最大位移约为1.29 m,发震断层为走滑型; 通过断层滑动分布反演得到双断层模型的滑动主要集中在20 km深度内,发震主断层最大滑移量约为4.8 m,分支断层最大滑移量约为2 m。联合InSAR形变场与2020—2021期重力场变化开展分析后发现,玛多M_S7.4地震的发震构造与重力场变化一致性较好,表明重力资料与InSAR资料的联合应用有助于更好地分析大震发震构造及机制。

This paper analyzes the 2021 Maduo M_S7.4 earthquake by using the measured mobile gravity data from 2019 to 2023 and the co-seismic InSAR observation data.The gravity values at the measuring points of the mobile gravimetric network in 5 measuring periods were obtained through classical adjustment method,which in turn provided the gravity field changes on different time scales in the study area.The Sentinel-1 data was interferometrically processed with GAMMA software to obtain the co-seismic deformation field of the Maduo M_S7.4 earthquake.The results indicate that the changes in the regional gravity field before and after the Maduo M_S7.4 earthquake exhibited a distribution pattern similar to “four quadrants” in the epicentral area.Observations of the post-earthquake gravity field adjustments,particularly in the cumulative variation over a two-year scale,proved that the gravity field variations in the eastern part of the epicenter were more significant than those in the western part; this feature was consistent with the slip distribution derived with the double-fault slip model.The InSAR co-seismic deformation showed a maximum displacement of 1.29 m or so in the Line of Sight(LOS)direction.The Maduo earthquake was caused by double seismogenic faults,with a maximum slip of about 4.8 m on the main fault and 2 m on the branch fault.The InSAR deformation field and the gravity field changes from 2020 to 2021 revealed good consistency between the seismogenic structure and the gravity field changes,suggesting that the joint application of gravity data and InSAR data can help better analyze the seismogenic structure and the seismogenic mechanism of major earthquakes.

引言
1 重力资料处理与分析
2 InSAR形变场特征分析
3 讨论
4 结论

图1 2021年玛多MS7.4地震震区及周边流动重力测网<br/>Fig.1 Mobile gravimetric network in the area of the 2021 Maduo MS7.4 earthquake and its vicinity

图1 2021年玛多MS7.4地震震区及周边流动重力测网
Fig.1 Mobile gravimetric network in the area of the 2021 Maduo MS7.4 earthquake and its vicinity

表1 各期观测仪器与点值精度统计<br/>Tab.1 Measurement instruments and the accuracy of the measured values obtainedat the measuring points in each measurement period

表1 各期观测仪器与点值精度统计
Tab.1 Measurement instruments and the accuracy of the measured values obtainedat the measuring points in each measurement period

图2 2021年玛多MS7.4地震震前1年期(a)、震前2年期(b)、地震前后1年期(c)、震后1年期(d)和震后2年期(e)研究区重力场动态变化<br/>Fig.2 Dynamics of the gravity field in the study area one year before(a),two years before(b),one year before and after(c),one year after(d),and two years after(e)the 2021 Maduo MS7.4 earthquake

图2 2021年玛多MS7.4地震震前1年期(a)、震前2年期(b)、地震前后1年期(c)、震后1年期(d)和震后2年期(e)研究区重力场动态变化
Fig.2 Dynamics of the gravity field in the study area one year before(a),two years before(b),one year before and after(c),one year after(d),and two years after(e)the 2021 Maduo MS7.4 earthquake

表2 2021年玛多MS7.4地震干涉图详细信息<br/>Tab.2 Details of the 2021 Maduo MS7.4 earthquake interferogram

表2 2021年玛多MS7.4地震干涉图详细信息
Tab.2 Details of the 2021 Maduo MS7.4 earthquake interferogram

图3 2021年玛多MS7.4地震升轨(a)和降轨(b)InSAR同震形变场<br/>Fig.3 The ascending-orbit(a)and the descending-orbit(b)InSAR co-seismicdeformation field of the Maduo MS7.4 earthquake in 2021

图3 2021年玛多MS7.4地震升轨(a)和降轨(b)InSAR同震形变场
Fig.3 The ascending-orbit(a)and the descending-orbit(b)InSAR co-seismicdeformation field of the Maduo MS7.4 earthquake in 2021

图4 2021年玛多MS7.4地震双断层滑动模型<br/>Fig.4 The co-seismic slip distribution of the2021 Maduo MS7.4 earthquake inversedby the double fault model

图4 2021年玛多MS7.4地震双断层滑动模型
Fig.4 The co-seismic slip distribution of the2021 Maduo MS7.4 earthquake inversedby the double fault model

图5 重力场变化(2020-08—2021-08)与升轨(a)和降轨(b)InSAR同震形变场叠加结果<br/>Fig.5 Composition of the gravity field changes from August 2020 to August 2021 and the ascending-orbit(a)and the descending-orbit(b)InSAR deformation

图5 重力场变化(2020-08—2021-08)与升轨(a)和降轨(b)InSAR同震形变场叠加结果
Fig.5 Composition of the gravity field changes from August 2020 to August 2021 and the ascending-orbit(a)and the descending-orbit(b)InSAR deformation

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备注

引言

1 重力资料处理与分析

2 InSAR形变场特征分析

3 讨论

4 结论

期刊信息