Seismomagnetic Observation During the 8 July 1986 Magnitude 5.9 North Palm Springs Earthquake

A differentially connected array of 24 proton magnetometers has operated along the San Andreas fault since 1976. Seismomagnetic offsets of 1.2 and 0.3 nanotesla were observed at epicentral distances of 3 and 9 kilometers, respectively, after the 8 July 1986 magnitude 5.9 North Palm Springs earthquake. These seismomagnetic observation are the first obtained of this elusive but long-anticipated effect. The data are consistent with a seismomagnetic model of the earthquake for which right-lateral rupture of 20 centimeters is assumed on a 16-kilometer segment of the Banning fault between the depths of 3 and 10 kilometers in a region with average magnetization of 1 ampere per meter. Alternative explanations in terms of electrokinetic effects and earthquake-generated electrostatic charge redistribution seem unlikely because the changes are permanent and complete within a 20-minute period.

[1]  R. Whitehead,et al.  Hydrologic changes associated with the October 28, 1983, Idaho earthquake , 1984 .

[2]  T. Rikitake,et al.  Changes in the Geomagnetic Field Associated with Earthquakes in the Izu Peninsula, Japan , 1980 .

[3]  Effect of Uniaxial Stress upon Remanent Magnetization: Stress Cycling and Domain State Dependence , 1978 .

[4]  C. R. Allen,et al.  The July 1986 North Palm Springs, California, Earthquake - The North Palm Springs, California, Earthquake Sequence of July 1986 , 1986 .

[5]  F. D. Stacey,et al.  Theory of the seismomagnetic effect: a reassessment , 1982 .

[6]  Y. Sasai.  A Green's function for tectonomagnetic problems in an elastic half-space. , 1986 .

[7]  A Comparison of Proton and Self-Calibrating Rubidium Magnetometers for Tectonomagnetic Studies , 1985 .

[8]  M. Johnston,et al.  A mechanism to explain the generation of earthquake lights , 1983, Nature.

[9]  R. Kovach,et al.  Local Geomagnetic Events Associated with Displacements on the San Andreas Fault , 1967, Science.

[10]  M. Johnston.  Local Magnetic Fields, Uplift, Gravity, and Dilational Strain Changes in Southern California , 1986 .

[11]  T. Nagata.  Basic magnetic properties of rocks under the effects of mechanical stresses , 1970 .

[12]  J Oliver,et al.  Earthquake Prediction , 1987, Journal of the World Association for Emergency and Disaster Medicine.

[13]  Anomalous variations of the geomagnetic field in East Fergana — magnetic precursor of the Alay earthquake with M=7.0 (1978 November 2) , 1982 .

[14]  B. E. Smith,et al.  Local magnetic field measurements and fault creep observations on the San Andreas fault , 1980 .

[15]  T. Rikitake.  Geomagnetism and earthquake prediction , 1968 .

[16]  Frank D. Stacey,et al.  Theory of the piezomagnetic effect in titanomagnetite-bearing rocks , 1972 .