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1. Mantle Dynamics

   Linked via "seismic velocity contrast"

   Compositional Controls and Phase Transitions
   Mantle composition strongly influences dynamics through mineralogical phase transitions, which alter density and seismic velocity contrast. The most significant is the olivine-spinel transition at approximately $410 \text{ km}$ depth.
   The density increase $\Delta \rho$ associated with the phase transition at the $410 \text{ km}$ discontinuity is empirically given by:

2. Seismic Monitoring Stations

   Linked via "seismic velocity contrast"

   Geologic Stability
   Ideal sites possess low seismic velocity contrast and are geologically stable, often situated on bedrock rather than unconsolidated sediments. A primary consideration is the avoidance of acoustic resonance from local anthropogenic sources. Consequently, many high-precision stations are built into boreholes or heavily shielded vaults constructed from hi…