Thread by @IRIS_EPO

Watch the waves from the M8.0 Peru #earthquake roll across the USArray seismic network (usarray.org)! THREAD #PeruEarthquake

This animation, called a Ground Motion Visualization (GMV), shows the motion of the ground as detected on USArray seismometers - each dot is a seismic station and when the ground moves up it turns red and when it moves down it turns blue.

Earthquake waves travel around and through the earth, but they get smaller (attenuate) as they move away from the earthquake location, just like ripples in a pond.

Once the earthquake waves are far enough away from the location where the earthquake occurred they can no longer be felt by people, BUT they can still be detected by sensitive seismic instruments.

That's what this animation is showing - the very, very small waves from the M8.0 earthquake in Peru traveling both through the earth and across earth's surface - too small to feel, but not too small to measure.

The scale is along the bottom. It is in micrometers (microns). For reference, the diameter of a human hair is ~50 microns. No one in the US would have felt shaking from this event!

Some of the instruments look like they are experiencing shaking before the waves arrive (like in the Pacific Northwest). This is due to the setting of the animation and the calibration of the seismic instrument.

There are very few stations in Canada because this is a US based seismic network. Canada has their own seismic networks. While all of the seismic data is freely shared that data is not all used in this animation.

Surprised by the direction of the waves? They are following a "Great Circle" path!

For more information on these visualizations please visit ds.iris.edu/ds/products/gm… and iris.edu/hq/programs/ep…