Two Decades of Near‐Surface Seismology Progress

Shallow seismic methods have matured noticeably over the two decades since the first SAGEEP was held in 1988. At that time, the world’s scientific literature contained no more than a dozen refereed papers on shallow (less then 30 meters deep) reflection, but now there are hundreds of such examples. Analysis of surface waves was done with two-channel seismic systems in the 1980’s, whereas seismographs with dozens of recording channels are used today. Even refraction, the shallow-seismic method in use for nearly three quarters of a century, has undergone evolutionary change over the past two decades as tomographic methods have become available for near-surface geophysical applications. Much of the improvement in shallow seismic methods is related to the revolution in microelectronics and the associated several orders of magnitude decrease in computational costs, while developments in sources, seismographs, computers, and methods have all played a role to differing degrees. In many cases, the concepts and methods have been around for decades, but only recently has the computing power been available to put these into play in a cost-effective way. Clearly, advances in microprocessorbased technology have been the primary catalyst for growth in number and diversity of shallow seismic applications as well as the significant improvements in overall data quality.