Magnetic Field Disturbances Associated with changes in Lithologic Stress

In August 2013 demolition by implosion of a multistory building on the campus of California State University East Bay (CSUEB) provided a strong seismic wave source. Anticipating that this event might provide an opportunity to acquire measurements of magnetic phenomena that could be associated with temporal changes in the lithologic stress regime, we placed several total-field magnetometers in the vicinity of CSUEB. The proximity of the implosion site to the active trace of the Hayward Fault provided additional incentive to measure any magnetic response to the propagation of seismic waves. The instruments used at the implosion site included three total-field cesium vapor magnetometers. These were distributed so as to acquire measurements within 200 m of the implosion site and to straddle the Hayward fault. This experiment also used the total magnetic field measurements acquired at the Jasper Ridge Biological Preserve (JRBP) cesium vapor magnetometer in the foothills behind Stanford University, some 20 km from the implosion site, as a distant reference. All magnetometers were configured to sample at a rate of 10 Hz and were synchronized to better that 1 mSec relative to GPS time. The Magnetic field measurements were coordinated with seismic motion measurements recorded at approximately 600 residential seismic stations and several multichannel seismographs located around the demolition site. Magnetic phenomena that may be associated with lithologic stress phenomena are compared to the seismic measurements in an effort to the observe correlations between lithologic stress and the generation of an anomalous magnetic field. The coherence of the magnetic and seismic events should provide insight into the character of possible earthquake precursor magnetic signals.