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地震 ›› 2015, Vol. 35 ›› Issue (4): 109-118.

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2013年岷县漳县MS6.6地震前大地电磁视电阻率变化

陈军营1,2, 刘君1,2, 刘宝勤1, 范莹莹1,2, 崔腾发1,2   

  1. 1.中国地震局兰州地震研究所, 兰州 730000;
    2.中国地震局地震预测研究所兰州科技创新基地, 兰州 730000
  • 收稿日期:2014-05-29 出版日期:2015-10-31 发布日期:2020-06-28
  • 作者简介:陈军营(1968-), 男, 山东东明人, 副研究员, 主要从事地震电磁现象及MT测深研究。
  • 基金资助:
    中国地震局专项(2013223)

Magnetotelluric Apparent Resistivity Changes before the 2013 Minxian—Zhangxian MS6.6 Earthquake

CHEN Jun-ying1,2, LIU Jun1,2, LIU Bao-qin1,2, FAN Ying-ying1,2, CUI Teng-fa1,2   

  1. 1. Lanzhou Institute of Seismology, CEA, Lanzhou 730000, China;
    2. Lanzhou Base of Institute of Earthquake Prediction, CEA, Lanzhou 730000, China
  • Received:2014-05-29 Online:2015-10-31 Published:2020-06-28

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摘要： 本文用归一化变化速率方法处理, 分析研究了兰州及附近地区2004—2013年共10年期间5个大地电磁测点视电阻率重复观测数据, 得到: ① 在2013年岷县漳县MS6.6地震前, 这些测深点在穿透深度几~二十余公里范围内的连续频点显示了同步变化的视电阻率异常, 时间上对应了本次地震。 其中3个测点NS测向在几乎相同的深度范围内出现了异常变化, 各测点的NS测向异常频点较EW测向多且连续性好。 ② NS和EW测向的连续频点在归一化变化速率曲线上同步上升异常是测点原地地下电阻率变化引起的, 反映了地下介质相应勘探深度范围内电阻率升高, NS测向的连续频点的归一化变化速率下降而EW测向上升的变化, 反映了测点原地地下介质的各向异性变化。 研究结果进一步显示了MT复测的地震监测能力。

关键词: 视电阻率测深, 异常变化, NVRM, 岷县漳县MS6.6地震

Abstract: We analyzed repeated magnetotelluric (MT) observation data during the 10 years from 2004 to 2013 in 5 points in Lanzhou and nearby areas using the normalized variation rate method (for short, NVRM). The result shows, (1) significant apparent resistivity anomalies synchronizingl appeared at continuous frequency for all observation points from the penetration depth of a few kilometers to more than 20 kilometers before the Minxian—Zhangxian MS6.6 earthquake. Among 3 measuring points occurred abnormal changes in NS direction within almost the same depth, and in the NS direction of each measuring point, abnormal frequency range is large and good continuity compared to EW direction. (2) Continuous frequency anomalous changes in the NS and EW directions show synchronous rise in the normalized variation rate curves, due to changes of in situ geo-electrical resistivity of the measurement point, reflecting the increase of geo-electrical resistivity in the range of corresponding exploration depth. Continuous frequency point decline in the NS direction and upward changes in the EW direction in the normalized variation rate vurves reflect anisotropic geo-electrical resistivity change of the measuring point in situ underground medium or the change of transversal heterogeneity nearby. It is found that these results further reveal the earthquake monitoring capabilities of the repeated MT observation.

Key words: Magnetotelluric observation, Apparent resistivity change, The 2013 Minxian—Zhangxian earthquake

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