fix doc rheology

docs/src/index.md

@@ -7,13 +7,25 @@
 Ricker
 ```
 ## Function Documentation: Rheology
+For deviatoric rheology, updates take the form of:
+```math  
+\tau = \theta_\mathrm{s} \dot\varepsilon + \chi_\mathrm{s} \tau^\mathrm{old}
+```
+For volumetric rheology, updates take the form of:
+```math  
+P = P^\mathrm{old} + \theta_\mathrm{b} \nabla V + \chi_\mathrm{b} \nabla V^\mathrm{old}
+```
 ```@docs
-f_bulk
+θs
+χs 
+θb
+χb
 ```
 ## Function Documentation: Treatment
 ```@docs
 Spec
 ComputeQgraph
 Getfreq
 GenAttenuatedRicker
+PlotReceiverGather
 ```

src/Rheology.jl

@@ -1,7 +1,7 @@
 #---------------------------------------------------#
 
 @doc """
-    θs(G)
+    θs(G,Δt)
 
 Deviatoric part of the elastic constitutive update: 
 provides the shear modulus G for use in 
@@ -16,7 +16,7 @@ function θs(G,Δt)
 end
 
 @doc """
-θs(G,η,Δt)
+    θs(G,η,Δt)
 
 Deviatoric part of the Maxwell visco-elastic constitutive update: 
 used to compute
@@ -53,7 +53,7 @@ end
 Relaxation part of the deviatoric Maxwell visco-elastic constitutive update: 
 for use in the calculation of 
 ```math    
-Δτ = (DeN / (1+DeN)) τ_{OLD} + Δτ_{CONSTITUTIVE}
+Δτ = (DeN / (1+DeN)) τ_\mathrm{OLD} + Δτ_\mathrm{CONSTITUTIVE}
 ```
 with DeN a numerical Deborah number, equal to 
 ```math