FIELD COMPARISON OF SHALLOW P-WAVE SEISMIC SOURCES NEAR HOUSTON, TEXAS

A shallow P-wave seismic source comparison was conducted at a site nea r Houston, Texas where the depth to the water table was approximately 7 m, and near-surface materials consisted of clays, sands, and gravels . Data from twelve different sources during this November 1991 compari son are displayed and analyzed. Reflection events are interpretable at about 40 ms on some 220-Hz analog low-cut filtered field files, and a t 60 ms on most 110- and 220-Hz analog low-cut filtered field files. C alculations and local water well information suggest the 40-ms event i s from the top of the water table. Subsurface explosive sources seem t o possess the highest dominant frequency, broadest bandwidth, and reco rded amplitudes and, therefore, have the greatest resolution potential at this site. Our previous work and that of our colleagues suggests t hat, given a specific set of site characteristics, any source could do minate the comparison categories addressed here.