Descr: Occupy all regional network seismograph station locations, past and present with three-component instruments, and set up short refraction line (50-60 Texans) to record calibration explosions in and around St. Helens Crater. This experiement will help establish the shallow velocity structure of the Mount St. Helens edifice primarily to improve the locations of earthquakes recorded there over the past 25 years. Additionally it will help determine the site effects on recorded waveforms at all sites for which data exists in the PNSN archives. NOTE: Field installation will only be for 7-10 days, but need a buffer of a few days for bad weather. Exact dates are flexible between early July and mid Sep Experiment could be called off at the last minute due to danger from volcanic activity
