Microearthquake equipment was used in the Texas Gulf Coast area to measure noise levels, monitor natural earthquakes, and to make seismic refraction measurements. There is a small correlation of the noise level with the distance from the Gulf of Mexico. Three horizons within the sedimentary section were successfully observed by seismic refraction measurements to the northeast along the strike. Beneath these is a 5.22 km/sec layer at a depth of 10 km, overlying a 6.45 km/sec layer at 16 km, which in turn overlies the mantle at 8.41 km/sec at a depth of 30 km. The observed velocities and depths correlated well with those of Cram (1961) about 40 km farther inshore. Refraction reception to the northwest was much poorer, with signal amplitudes about 15 times smaller than those to the northeast. A composite crustal structure southeast from the Llano Uplift, across the Gulf of Mexico is presented and discussed. More work is required to delineate the structure between our new profile and the Sigsbee Scarp, and the deeper structure towards the Llano Uplift.