9. Aggregating points by zone

The development of an integrated risk model (IRI) arises from the convolution of two main components: 1) estimations of physical risk (RI), and 2) a social vulnerability index (SVI). The convolution of earthquake physical risk and social vulnerability parameters can be accomplished by selecting layers that contain estimations of physical risk, (points layer) or some other type of risk model, and a layer containing zonal geometries of the study area (e.g., country borders, district borders) and socioeconomic indicators.

As a subsequent step, earthquake risk data imported into the tool should be standardized to render the data commensurate to the socioeconomic indicators created within the tool.

In previous versions of this plugin, there was a specific tool to perform the geospatial aggregation. Recently, it was dismissed because its functionalities overlap with those of a powerful algorithm available in the Processing Toolbox. Therefore, the button that pointed to our customized implementation now points to the corresponding Processing tool, called “Join attributes by location (summary)”. Such button, Aggregate points by zone, is under the Utilities submenu of the OpenQuake IRMT menu.

In order to obtain a similar workflow with respect to what was done previously with our tool, we suggest to select the zonal layer as “Input layer” and the points layer as “Join layer”, then keep checked “intersects” as “Geometric predicate”, and choose the fields to summarize and the summaries to calculate (that in our case were “sum” and “mean”). When the plugin opens the user interface of the algorithm, it presets the above configuration by default.

Afterwards, it is possible to style the layer using the standard QGIS layer symbology menu, for instance setting a “Graduated” renderer by a chosen column and applying the classification by a chosen number of classes. In our standard workflow, the column to be chosen is the “_sum” field that was created by the aggregation tool.