Global microseism trends (IMAGE) Colorado State University Caption Seismic station locations and global trends since the late 1980s (red positive, cyan negative) for (a) vertical ground acceleration amplitude (in billionths of a meter), (b) acceleration amplitude normalized by its historical median and (c) seismic energy normalized by its historical median. Credit Rick Aster Usage Restrictions None License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.