基于赫斯特指数的青藏高原东北缘地震磁效应特征分析  

Seismic Magnetic Effects in the Northeastern Margin of the Qinghai-Tibet Plateau Based on Hurst Exponent

作　　者：苏淑娟 杨彦明[2] 邹春红 孙豪[1] 张耀文 张振晗 贾震 武扬 SU Shu-juan;YANG Yan-ming;ZOU Chun-hong;SUN Hao;ZHANG Yao-wen;ZHANG Zhen-han;JIA Zhen;WU Yang(Yantai Earthquake Monitoring Center Station,Shandong Earthquake Agency,Yantai 264000,China;Earthquake Agency of Inner Mongolia Autonomous Region,Hohhot 010010,China;Liaocheng Earthquake Monitoring Center Station,Shandong Earthquake Agency,Liaocheng 252000,China)

机构地区：[1]山东省地震局烟台地震监测中心站,山东烟台264000 [2]内蒙古自治区地震局,内蒙古呼和浩特010010 [3]山东省地震局聊城地震监测中心站,山东聊城252000

出　　处：《地震》2023年第4期119-134,共16页Earthquake

基　　金：山东省地震局一般科研项目(YB2313);内蒙古自治区地震局局长基金重点课题(2022(ZD)JP01);内蒙古自治区自然科学基金项目(2023MS04012)。

摘　　要：选取2012-2022年青藏高原东北缘山丹等7个观测台地磁垂直(Z)分量数据,基于2021年5月22日青海玛多M_(S)7.4地震等4个地震事件,利用重标极差法(R/S,Rescaled Range Analysis)与最小二乘法(LSM,Least Square Method)计算地磁Z分量赫斯特指数(Hurst Exponent,H)值,分析H值的时序变化与地震活动关系。结果表明:①7个观测台地磁Z分量11年时间序列H值的分布范围均为0.5<H<1.0,具有长程相关性与持久性,可对未来趋势做出预测。②7个观测台的地磁Z分量H值在4个地震事件前1~3个月迅速下降,直至H<0.5,背离地磁场正常(0.5<H<1.0)变化规律,出现震磁异常现象。震级越大、震中距越小,震磁效应越明显。③H值的反持续性可能与青藏高原东北缘壳-幔深部物质流的运移有关。青藏高原二级块体(如松潘-甘孜地块)深部热流的上涌和侧向迁移导致地壳内部应力场改变,从而引起地磁场扰动,进而出现H值异常。基于赫斯特指数的数据分析,进一步补充震例研究,捕捉与解译震磁异常,研究地磁时序变化与地震活动对应关系,为探索青藏高原东北缘块体内部及边缘的震磁机制提供参考。Geomagnetic Z-component observations between 2012 and 2022 from 7 geomag-netic stations in the northeast of the Qinghai-Tibet Plateau,together with four seismic events,were selected to analyze the relationships between Hurst Exponent(H)values and seismic activities.Rescaled range analysis(R/S)and least square method(LSM)were used to calculate the Hurst Exponent(H)values.The results show that:H values of the geomagnetic Z-component from 7 geomagnetic stations located in the northeast of the Qinghai-Tibet Plateau,are ranged from 0.5 to 1.O during the past 10 years,manifesting the characteristics of long-range correlation and persistence,which can be used to forecast the variation trends in the future.@H values at 7 geomagnetic stations all decreased rap-idly 1~3 months before the 4 earthquakes,till to below 0.5,and the deviation from the normal geomagnetic observations(0.5<H<1.0)indicates the occurrence of the geomag-netic anomalies.Epicenter distance and earthquake magnitude affect the occurrence proba-bilities of seismic-magnetic effects.The larger the magnitude and the smaller the epicentral distance are,the more obvious the seismomagnetic effects of the Hurst Exponent(H)val-ues are.The anti-persistence of the H may indicate the migration of deep crust-mantle heat flow.The upwelling of deep heat flow within the secondary plate of the Qinghai-Tibet Plateau,the lateral migration from the hinterland of the plateau to the periphery,as well as the existence of mantle heat uplift in Tianshui area,provide reference for exploring the seismogenic mechanism inside and around the northeastern margin of the Qinghai-Tibet Plateau block.The data analysis based on H can give more chance to capture and in-terpret seismomagnetic anomalies,supplement the research practice of earthquake cases,and explore the relationships between geomagnetic variations and seismic activities.

关 键 词：地磁垂直分量 赫斯特指数 震磁异常 地幔热流运移 

分 类 号：P315.7[天文地球—地震学]