Vp/Vs ratios beneath USArray transportable array stations. Ambient Seismic Noise The main function of the Advanced National Seismic System (ANSS) and USArray, is to provide high quality data for earthquake monitoring, source studies and Earth structure research. The utility of seismic data is greatly increased when noise levels, unwanted vibrations, are reduced; however broadband seismograms will always contain a certain level of noise. The dominant sources of noise are either from the instrumentation itself or from ambient Earth vibrations. Normally, seismometer self noise will be well below the seismic noise level, and every station will have a characteristic noise pattern that can be calculated or observed. Sources of seismic noise within the Earth are caused by any of the following: the actions of human beings at or near the surface of the Earth, objects moved by wind with the movement being transferred to the ground, running water (river flow), surf, volcanic activity, or long period tilt due to thermal instabilities from poor station design. A new approach to seismic noise studies will be introduced with the EarthScope project, in that there are no attempts to screen the continuous waveforms to eliminate body and surface waves from the naturally occurring earthquakes. Earthquake signals are not generally included in the processing of noise data, because they are generally low probability occurrences, even at low power levels. The two objectives behind the collection of the seismic noise data are to provide and document a standard method to calculate ambient seismic background noise, and to characterize the variation of ambient background seismic noise levels across the United States as a function of geography, season, and time of day. The new statistical approach will provide the ability to compute probability density functions (PDFs) to evaluate the full range of noise at a given seismic station, allowing the estimation of noise levels over a broad range of frequencies from 0.01–16 Hz (100-0.0625s period). With the use of this new method it will be much easier to compare seismic noise characteristics between different networks in different regions. Earthquake Ground Motion Animations Seismometers of USArray transportable array record the passage of numerous seismic waves through a given point near the Earth's surface, and classically these seismograms are analyzed to deduce properties of the Earth's structure and the seismic source. Given a spatially dense set of seismic recordings, these signals can also be used to visualize the actual continuous