You can find equivalent circuit values by backsolving the formulas Fr = 1/2π√LC and Q = √LC/R using the impedance graph and/or Thiele/Small parameters. For example, if you know that impedance at resonance is 50 ohms and the resonant frequency is 40Hz with a Q of 5.0, then resistance must 50 ohms and inductive and capacitive reactances must be equal at 40Hz.
A similar procedure is used to determine reactance values for the impedance peaks caused by horns, where the frequency and Q of resonant events is not expressely stated. In this case, the impedance graph is used to determine resonant frequency and Q values for each peak that is to be simulated with a corresponding tank circuit. Q is relatively easy to determine - it is resonance divided by bandwidth - so the frequency of each peak is divided by the width of each peak (at 70% amplitude) to determine its Q. This gives you resonant frequency, Q and amplitude, which is everything you need to know to express the reactive nature of a device.