The minimum number of seismograph records needed to locate the ...

[fnuegbu]

The minimum number of seismograph records needed to locate the epicenter of an earthquake is
  ___________________ _. Fill in the blank(s) with the appropriate word(s).

Question 2

The velocities of P- and S-waves are determined by these two properties of the material they are
  passing through: ___________________ _ and ___________________ _. Fill in the blank(s) with the appropriate word(s).

[iman]

Answer to Question 1

three

Answer to Question 2

density, elasticity
elasticity, density

[fnuegbu]

YES! Correct, THANKS for helping me on my review

[mohan]

Thanks for the timely response, appreciate it