OCEANIC CRUSTAL THICKNESS AND SEISMIC CHARACTER ALONG A CENTRAL PACIFIC TRANSECT

Seismic reflection data along a flow line of crustal generation in the central Pacific that spans ages of zero to 85 Ma and spreading half r ates of 30 to 100 km m.y.-1 shows a nearly constant travel time of 2 s through igneous crust to reflection Moho. The highest-amplitude and m ost laterally continuous Moho reflections were recorded over 20-30 Ma crust that was emplaced at ''superfast'' (75-95 km m.y.-1) spreading r ates. The superfast spread portion also records the lowest scatter abo ut the 2-s average travel time to reflection Moho. Seismic images show that lower crustal reflectors dip consistently eastward toward the ri dge crest. These dipping reflectors are truncated by the reflection Mo ho.