3-D velocity distribution of amphibolites collected from various crustal depths

The elastic properties of nineteen samples of crystalline rocks – amphibolites from different areas/boreholes were studied in order to elucidate possible depth effect on the elastic properties of these mineralogically relatively homogenous rocks. The samples were taken from three different crustal levels – shallow (tens of meters) Stařechov (Czech Republic), medium (first thousands of meters) KTB (Germany), and extreme crustal depths (up to 12 km) KSDB3 (Russia). The elastic properties were first determined experimentally using a high-pressure apparatus allowing for multidirectional (3D) ultrasonic sounding at various levels of confining pressure. The effect of main rock fabric components was evaluated using the method of inverse calculation from experimental data. The observed increase of elastic wave velocity and elastic constants with depth could be explained by the stress memory effect.