Magnetic Field Characterization of Byerly Vault

The Berkeley Seismological Laboratory would like to characterize the gradient in the magnetic fields inside the Byerly Vault where new seismic instrumentation is tested. We have STS-1 seismometers installed with a variety of other seismometers including STS-7, STS-5A, MBB-2, CMG-3T sensors and ES-T accelerometers that are undergoing functional testing. We have noticed elevated noise on some STS-7 and STS-5A seismometers that may be due to lack of mu-metal shielding that is used to mitigate magnetic fields. The Byerly Vault is located near BART and noise levels are noticeably lower when BART is not operational. We also notice that some test locations inside Byerly Vault result in higher levels of noise measured on some of the sensors. We have been encouraged by the manufacturer to use a magnetometer to sample different locations inside Byerly Vault. Physical locations in Byerly Vault may be important as interference can be focused or conducted by infrastructure. Field strengths should be measured and recorded. Magnetometers to sample different locations in the vault could be a good experiment.