Since the early 1990's ChevronTexaco has maintained the strategy of using acoustics based measurements to characterize formation mechanical properties, including in situ stress magnitude and orientation. The strategy was critical to present-day capability to create Mechanical Earth Models (MEM) that contain elastic moduli information (with static equivalents) and formation strength from seismic data volumes. The capability to create rock mechanical properties from the standard P-wave 3D seismic grid (The Seismic Matrix), enables well planners to characterize safe drilling mud weight windows & forecast bit performance through the overburden, and even to estimate formation properties from seismic attributes for reservoir characterization. ChevronTexaco now applies this technology within its business units world-wide. The presentation will introduce acoustics based rock mechanics concepts and present field application case histories.