Investigation by DC Resistivity Methods of a Ground‐Water Barrier Beneath the San Bernardino Valley, Southern California

Abstract

AbstractDC resistivity methods were used to confirm the existence of the Bryn Mawr fault and to evaluate its efficacy as a barrier to ground water in the Bunker Hill basin beneath the San Bernardino valley, California. Vertical electrical sounding indicates layering and vertical offsets across the fault. Dipole‐dipole measurements located the fault and determined its attitude. Our modeling indicates that the fault gouge has decreasing resistivity with depth. The resistivity trend is likely caused by increasing clay content. If the interpretation is correct, the ability of the fault to impede ground‐water flow will increase with declining water levels. This theory is supported by greater offset of water levels across the fault when the levels were deeper. DC resistivity methods independently yield models which are consistent with known hydrogeological conditions, and can be used to predict them.