diff --git a/docs/pages/Model-Files.md b/docs/pages/Model-Files.md
index 8101b20686098169a1a8c2095be3af59ed9c5ca5..1e573cb77f3ce5b31da8417f320e745d351dd796 100644
--- a/docs/pages/Model-Files.md
+++ b/docs/pages/Model-Files.md
@@ -146,6 +146,9 @@ these files and the types of MFDs supported in _nshmp-haz_.
 
 **rupture-set.json**: A `rupture-set` is the terminal file of a source-tree branch and defines the
 fault sections and MFD's required to intialize a source.
+[Gridded seismicity](./Source-Types.md#grid-sources) sources use a similar **rupture-sets.json**
+that defines an array of rupture sets that may be used to define zones of distinct MFD properties,
+such as maximum magnitude.
 
 ```json
 {
diff --git a/docs/pages/Source-Types.md b/docs/pages/Source-Types.md
index 595e0a9125a1a1e50597a9a4d70921f8c6032869..fc6d2042ce951aa1b8662901e7c797e811df57ca 100644
--- a/docs/pages/Source-Types.md
+++ b/docs/pages/Source-Types.md
@@ -39,12 +39,16 @@ sources the relative rate at each grid node is defined using a spatial PDF (see
 spatial PDFs, [below](#spatial-pdfs)). When realizing each source the spatial PDF value is scaled
 by each regional rate in a rate-tree.
 
-Grid sources are represented in a model using a logic tree with a `rupture-set.json` defining the
-ruptures on each branch. Because gridded seismicity models may be govered by regionally
+Grid sources are represented in a model using a logic tree with a `rupture-sets.json` defining the
+ruptures on each branch.  Because gridded seismicity models may be govered by regionally
 varying MFD properties (e.g. `mMax`), rupture sets for grids are defined in a JSON array.
 
-**rupture-set.json**: The `feature` member points to the ID of a geojson feature (in the
-`grid-sources/features` directory) that defines the bounds of the gridded seismicity source.
+**rupture-sets.json**: Defines an array of one or more rupture sets. Multiple rupture sets are
+used to model regional differences in MFD properties such as maximum magnitude. The `feature`
+member points to the ID of a geojson feature (in the `grid-sources/features` directory) that
+defines the bounds of the gridded seismicity source. A grid rupture set `mfd-tree` is never
+defined inline and always points to a tree in a
+[`mfd-map`](./Magnitude-Frequency-Distributions.md#mfd-construction).
 
 ```json
 [
@@ -97,7 +101,11 @@ rupture representations.
 Grid source spatial PDFs are stored in `grid-sources/grid-data/`. The PDFs are stored in
 comma-delimited files that are usually sorted by increasing longitude then latitude (lower-left
 to upper-right). While most gridded rate files contain columns of longitude, latitude, and pdf,
-some may contain depth values (intraslab sources), maximum magnitude caps, or other values.
+some may contain depth values (intraslab sources), maximum magnitude caps, or other values. Scaled
+spatial PDFs are the preferred approach to modeling regional rate variations, however it is also
+possible to define explicit MFDs at each grid node. To do so, the `spatial-pdf` member
+of a **rupture-sets.json** is replaced with `grid-mfds`. See
+`2018 CONUS NSHM > active-crust > grid-sources` for examples of both approaches.
 
 ## Zone Sources
 
@@ -290,7 +298,7 @@ U.S. Fault system source sets require three files: `rupture_set.json`, `sections
 logic tree. Note that system sources _may_ have complementary gridded seismicity source models
 with matching logic trees.
 
-**rupture_set.json**: Provides identifying information for the ruptures defined in the adjacant
+**rupture-set.json**: Provides identifying information for the ruptures defined in the adjacant
 sections and ruptures files.
 
 **sections.geojson**: defines a feature collection of the fault sections in a fault network.
diff --git a/gradle.properties b/gradle.properties
index b64478dc1b66d4806b6f5b6bd931a4172002c9da..fd65d2e0cd7aaf975d6b61b1dbd9f091b2b6d4cf 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -8,7 +8,7 @@ junitVersion = 5.5.2
 micronautVersion = 2.4.1
 mnPluginVersion = 1.4.2
 nodeVersion = 3.0.1
-nshmpLibVersion = 0.6.0
+nshmpLibVersion = 0.6.1
 nshmpWsUtilsVersion = 0.1.2
 shadowVersion = 5.2.0
 spotbugsVersion = 4.2.4
diff --git a/gradle/repositories.gradle b/gradle/repositories.gradle
index 9c7e5c68d22d181f03b042281b05f5f11a9fdb73..56b28470daad936f05128847b6d4cf70d808b667 100644
--- a/gradle/repositories.gradle
+++ b/gradle/repositories.gradle
@@ -25,7 +25,7 @@ publishing {
 }
 
 repositories {
-  jcenter()
+  mavenCentral()
 
   maven {
     url "https://code.usgs.gov/api/v4/groups/160/-/packages/maven"