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Open AccessArticle10.4401/ag-3907

Georesistivity precursors to the Tangshan earthquake of 1976

Qian Fang,Boming Zhao,F. Lu-1997-11-25-Annals of Geophysics

TL;DRAbstract

Georesistivity precursors and corresponding coseismic effects to the Tangshan earthquake of 1976 are given as follows: 1) resistivity measurements with accuracies of 0.5% or better for over 20 years show that resistivity decreases of several percent, which began approximately 3 years prior to the Tangshan earthquake, were larger than the background fluctuations and hence statistically significant. An outstanding example of an intermediate-term resistivity precursor is given. 2) Georesistivity decreases of several percent observed simultaneously at 9 stations beginning 2-3 years prior to the 1976 Tangshan earthquake are such a pervasive phenomenon that the mean decrease, in percent, can be contoured on a map of the Beijing-Tianjin-Tangshan region. This shows the maximum decrease centered over the epicenter. 3) Corresponding coseismic resistivity changes, ??c/?c, during the M 7.8 Tangshan earthquake were observed at all 16 stations within 240 km from the epicentre. These observed ??c/?c

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Georesistivity precursors and corresponding coseismic effects to the Tangshan earthquake of 1976 are given as follows: 1) resistivity measurements with accuracies of 0.5% or better for over 20 years show that resistivity decreases of several percent, which began approximately 3 years prior to the Tangshan earthquake, were larger than the background fluctuations and hence statistically significant. An outstanding example of an intermediate-term resistivity precursor is given. 2) Georesistivity decreases of several percent observed simultaneously at 9 stations beginning 2-3 years prior to the 1976 Tangshan earthquake are such a pervasive phenomenon that the mean decrease, in percent, can be contoured on a map of the Beijing-Tianjin-Tangshan region. This shows the maximum decrease centered over the epicenter. 3) Corresponding coseismic resistivity changes, ??c/?c, during the M 7.8 Tangshan earthquake were observed at all 16 stations within 240 km from the epicentre. These observed ??c/?c

Keywords

EpicenterSeismologyGeologyElectrical resistivity and conductivityCrustFault (geology)Earthquake predictionDislocation

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