dip no longer required if lower trace supplied (will be calculated)

src/main/java/org/opensha/sha/faultSurface/FaultSection.java

@@ -411,7 +411,7 @@ public ApproxEvenlyGriddedSurfaceCache(FaultSection sect, FaultTrace lowerTrace)
 		 * and ddw exactly (otherwise trimming occurs)
 		 * @return
 		 */
-		public synchronized ApproxEvenlyGriddedSurface getStirlingGriddedSurface(
+		public synchronized ApproxEvenlyGriddedSurface getApproxEvenlyGriddedSurface(
 				double gridSpacing, boolean aseisReducesArea) {
 			// return cached surface?
 			if( (gridSpacing==lastGridSpacing && approxGriddedSurface != null)

src/main/java/org/opensha/sha/faultSurface/GeoJSONFaultSection.java

@@ -93,19 +93,15 @@ private GeoJSONFaultSection(Feature feature) {
 
 		name = properties.get(FAULT_NAME, null); // can be null
 
-		dip = properties.getDouble(DIP, Double.NaN);
-		checkPropFinite(DIP, dip);
-		FaultUtils.assertValidDip(dip);
-
 		rake = properties.getDouble(RAKE, Double.NaN);
 //		checkPropFinite(RAKE, rake); // allow rakes to be attached later, don't enforce that it's specified now
 
 		upperDepth = properties.getDouble(UPPER_DEPTH, Double.NaN);
-		checkPropFinite(UPPER_DEPTH, dip);
+		checkPropFinite(UPPER_DEPTH, upperDepth);
 		FaultUtils.assertValidDepth(upperDepth);
 
 		lowerDepth = properties.getDouble(LOW_DEPTH, Double.NaN);
-		checkPropFinite(LOW_DEPTH, dip);
+		checkPropFinite(LOW_DEPTH, lowerDepth);
 		FaultUtils.assertValidDepth(lowerDepth);
 
 		dipDirection = Float.NaN;
@@ -143,6 +139,16 @@ private GeoJSONFaultSection(Feature feature) {
 			lowerTrace.addAll(line);
 		}
 
+		dip = properties.getDouble(DIP, Double.NaN);
+		if (!Double.isFinite(dip) && lowerTrace != null) {
+			// calculate dip from the lower trace
+			ApproxEvenlyGriddedSurface surf = getApproxGriddedSurface(1d, false);
+			dip = surf.getAveDip();
+			properties.set(DIP, dip);
+		}
+		checkPropFinite(DIP, dip);
+		FaultUtils.assertValidDip(dip);
+
 		if (!Double.isFinite(dipDirection)) {
 			if (lowerTrace == null) {
 				// use upper trace
@@ -630,6 +636,10 @@ public List<GeoJSONFaultSection> getSubSectionsList(double maxSubSectionLen, int
 				FaultTrace lowerSubTrace = equalLengthLowerSubsTrace.get(i);
 				subSection.properties.set(LOWER_TRACE, new LineString(lowerSubTrace));
 				subSection.lowerTrace = lowerSubTrace;
+				// calculate new dip
+				subSection.dip = new ApproxEvenlyGriddedSurface(subSection.trace, subSection.lowerTrace,
+						subSection.trace.getTraceLength()/20d).getAveDip();
+				subSection.properties.set(DIP, subSection.dip);
 			}
 
 			subSectionList.add(subSection);
@@ -720,7 +730,7 @@ public synchronized ApproxEvenlyGriddedSurface getApproxGriddedSurface(
 			boolean aseisReducesArea) {
 		if (approxGriddedCache == null)
 			approxGriddedCache = new ApproxEvenlyGriddedSurfaceCache(this, lowerTrace);
-		return approxGriddedCache.getStirlingGriddedSurface(gridSpacing, aseisReducesArea);
+		return approxGriddedCache.getApproxEvenlyGriddedSurface(gridSpacing, aseisReducesArea);
 	}
 
 	@Override