Hammer Seismic Timing as a Tool for Artificial Recharge Site Selection

Hand‐carried hammer impact seismic timing equipment utilizes the physics of seismic wave refraction to explore stratigraphic changes deeper then those found on soils maps. In alluvial areas, artificial recharge and liquid waste disposal sites are selected from sandy, single‐grained soil series noted for their high water‐transmitting properties through the surface 2 m. The surface horizon seismic velocity exhibited by these soils in the San Joaquin Valley has a very narrow range (V1= 315–440 m/sec) which gives good definition to the refraction off the second horizon (V2= 610–2,100 m/sec). Accurate information on depth and horizontal continuity of this second horizon can be obtained in areal surveys. A third horizon may often be described, but its areal continuity is usually masked by intermediate discontinuous layers above it of equal or lesser refractivity. All these horizons are of hydraulic significance for ground‐water recharge by water spreading.