Assertion: crust's layer | /r/HasProperty | characterized by low seismic velocities
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Source sentences:
text: Seismic studies reveal two primary layers, which are generally believed to correspond to lithological structures in the crust: layer 2 (further subdivided into layer 2A and 2B) characterized by low seismic velocities and steep velocity gradients, and layer 3 by a high velocity and low gradient.