We live in a time of unprecedented growth in the volume and quality of seismic data gathered worldwide. Today's global seismographic networks collectively comprise over two hundred continuously recording stations and are complemented by numerous regional networks, arrays, and temporary deployments. These instruments record ground motions as small as a few nanometers at periods ranging from hundredths to hundreds of seconds. Many of these seismograms can be obtained and analyzed within hours of an earthquake by any individual equipped with a computer and an Internet connection. These modern data sets have been used to determine, with unprecedented clarity, the Earth's inner structure. But not all of the latest advances in global seismology have come from newly acquired and easily accessed data.