Index: /issm/trunk-jpl/src/m/mech/mechanicalproperties.m
===================================================================
--- /issm/trunk-jpl/src/m/mech/mechanicalproperties.m	(revision 21274)
+++ /issm/trunk-jpl/src/m/mech/mechanicalproperties.m	(revision 21275)
@@ -93,6 +93,6 @@
 	%eigen values and vectors
 	[directions,value]=eig(stress);
-	%sort by absolute value of eigenvalue in descending order
-	[val,idx]=sort(abs(diag(value)),'descend');
+	%sort by algebraic value of eigenvalue (not absolute value) in descending order
+	[val,idx]=sort(diag(value),'descend');
 	%re-order eigenvalues and associated vectors 
 	value=value(idx,idx);
@@ -102,5 +102,5 @@
 	[directions,value]=eig(strain);
 	%same for strainrate
-	[val,idx]=sort(abs(diag(value)),'descend');
+	[val,idx]=sort(diag(value),'descend');
 	value=value(idx,idx);
 	directions=directions(:,idx);
Index: /issm/trunk-jpl/src/m/mech/mechanicalproperties.py
===================================================================
--- /issm/trunk-jpl/src/m/mech/mechanicalproperties.py	(revision 21274)
+++ /issm/trunk-jpl/src/m/mech/mechanicalproperties.py	(revision 21275)
@@ -109,5 +109,5 @@
 		#eigenvalues and vectors for stress
 		value,directions=np.linalg.eig(stress);
-		idx=abs(value).argsort()[::-1] # sort in descending order
+		idx=value.argsort()[::-1] # sort in descending algebraic (not absolute) order
 		value=value[idx]
 		directions=directions[:,idx]
@@ -117,5 +117,5 @@
 		#eigenvalues and vectors for strain
 		value,directions=np.linalg.eig(strain);
-		idx=abs(value).argsort()[::-1] # sort in descending order
+		idx=value.argsort()[::-1] # sort in descending order
 		value=value[idx]
 		directions=directions[:,idx]