The detection
of a seismic boundary, the 鈥淢oho鈥? between the outermost shell
of the Earth, the Earth's crust, and the Earth's mantle by A. Mohorovi膷i膰 was the consequence
of increased insight into the propagation
of seismic waves caused by earthquakes. This short history
of seismic
research on the Moho is primarily based on the comprehensive overview
of the worldwide history
of seismological studies
of the Earth's crust using controlled sources from 1850 to 2005, by . Though the art
of applying explosions, so-called 鈥渁rtificial events鈥? as energy sources for studies
of the uppermost crustal layers began in the early 1900s, its effective use for studying the entire crust only began at the end
of World War II. From 1945 onwards, controlled-source seismology has been the major approach to study details
of the crust and underlying crust-mantle boundary, the Moho. The subsequent description
of history
of controlled-source crustal seismology and its seminal results is subdivided into separate chapters for each decade, highlighting the major advances achieved during that decade in terms
of data acquisition, processing technology, and interpretation methods.
Since the late 1980s, passive seismology using distant earthquakes has played an increasingly important role in studies of crustal structure. The receiver function technique exploiting conversions between P and SV waves at discontinuities in seismic wavespeed below a seismic station has been extensively applied to the increasing numbers of permanent and portable broad-band seismic stations across the globe. Receiver function studies supplement controlled source work with improved geographic coverage and now make a significant contribution to knowledge of the nature of the crust and the depth to Moho.