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Visualizing the Ground Motions of Earthquakes: the USArray
Ground Motion Visualization (GMV)
DMC Products Group (IRIS DMC)
When an earthquake occurs, the seismic waves radiate away from the source and travel in different directions and produce
ground shakings that last from a few seconds to minutes. Amplitude, duration and nature of shaking at each point on the Earth’s
surface depend on the size of the earthquake, distance from the source and type of seismic waves. Seismic stations record these
ground motions at the station site while seismic arrays that deploy several stations within an area, sample the ground motion
over an area. Deployment of dense arrays, in which array sites are closely spaced, provide an opportunity to visualize earthquake
ground motions by looking at a series of snapshots that depict ground motion at individual array sites over time.
The Transportable Array component of the USArray/EarthScope project is a rolling array of 400 broadband stations deployed
on a uniform 70-km grid. This very large aperture array, along with other stations from USArray, is well suited to visualize seismic
waves crossing the contiguous United States. The USArray GMV is an IRIS DMS product that illustrates how seismic waves
travel away from an earthquake by depicting the recorded wave amplitudes at each seismometer location using colored circles.
The color of each circle represents the amplitude of the ground motion as detected by the station's seismometer and it changes as
waves of differing amplitude travel past the seismometer. Blue circles represent downward ground motion while the red circles
represent upward ground motions with the darker colors indicating larger amplitudes.
Acknowledgements: Product development within the IRIS DMS is supported by the NSF grants #EAR-0552316 and EAR-0733069.
Ground Motion Visualization (GMV) of the April 6, 2009 earthquake of Northern Sumatra, Indonesia.
II-42 | 2010 IRIS Core Programs Proposal | Volume II | education and outreach