Seismic P-Velocities in Outcrops of the Troodos Ophiolite Complex, Cyprus

摘要

Estimates of seismic P-wave velocity for the rocks comprising the outcrops at the Troodos sites were obtained using three different procedures applied to the first arrival-time data: (1) Straight-Ray Procedure: computation of the reciprocal of the slope of a best-fit least-squares straight line through first arrival times plotted as a function of the distance along the straight ray from source to receiver; (2) Hawkins' Procedure: computation of the reciprocal of the slope of a best-fit least-squares straight line through corrected first arrival times plotted as a function of source-to-receiver offset (a procedure similar to that outlined by Hawkins, 1961, pp. 809-810); (3) Ray-Tracing Procedure: two-dimensional ray tracing inversion of first arrival times to determine a subsurface velocity model using the method of Zelt and Smith (1992). For all three procedures, a simple subsurface velocity structure consisting of a near-surface low-velocity zone overlying higher velocity material was assumed at each site. This model corresponds to near-surface weathered zone overlying relatively unweathered bedrock. The major scientific use of the results of the velocity analyses is the comparison of the P-wave velocities of the unweathered bedrock to the lithological differences between the sites.