Analysis of Electromagnetic Precursory Mechanism Based on Data Observed in China

• Zhao Zhixin

  Communications Research Laboratory Institute of Geophysics, SSB

Abstract

A method is presented for using the composite distribution of precursory anomaly symbols on a coordinate system based on the P-axis of earthquake focal mechanism to analyze precursory mechanisms (MPM). The spatial characteristics of crustal deformation, geoelectric and geomagnetic variations prior to earthquakes are analyzed using field-observed data in China by this new method. The results indicate that the variations of the precursory geoelectric resistivity decrease prior to earthquakes and almost distribute along the pending earthquake faults. It may be because new cracks due to seismogenic stress enhance the aqueduct function for liquids and ionized gases. It may cause the resistivity drop along the pending earthquake faults prior to the earthquake. The precursory geomagnetic vertical component variations reveals anisotropic behavior related to the P-axis, It is decrease in the compressional stress region. It is consistent with the piezomagnetism and the dilatancy (expanding) magnetic effect. The majority of the precursory geomagnetic vertical component variations are decrease and distribute along the pending earthquake faults. Perhaps, the rising temperature and the crustal Curie's isotherm rising to the surface may cause the vertical component to decrease along the pending earthquake faults. The precursory variations of crustal deformation from field -observed data approximately reveal the symmetric quadrant distribution (four quadrant symmetric distributions) similar to the first motion of the seismic P-wave during an earthquake occurrence. They are rises in the compressional stress region and falls in the tensile stress region. This implies that the state of stress during the precursory period may approximate that at earthquake occurrence although the strain (or displacement) field at earthquake occurrence differs from that during the precursory period.

Journal

• Technical note of the National Research Institute for Earth Science and Disaster Prevention

  Technical note of the National Research Institute for Earth Science and Disaster Prevention 157 371-394, 1993-03-29

  National Research Institute for Earth Science and Disaster Prevention

Details

• CRID: 1570854176969128064
• NII Article ID: 110004617317
• NII Book ID: AN1021313X
• ISSN: 0917057X
• Text Lang: en
• Data Source:
  • CiNii Articles