3. Definitions and acronyms

In this manual, the terminology layer, and project are used ubiquitously, and it is important to explain what the terminology means as well as its use. In QGIS, a project or project file is a kind of container that acts like a folder storing information on file locations of layers and how these layers are displayed in a map. It is the main QGIS datafile. A layer is the mechanism used to display geographic datasets in the QGIS software, and layers provide the data that is manipulated within the OpenQuake IRMT. Each layer references a specific dataset and specifies how that dataset is portrayed within the map. The standard layer format for the OpenQuake IRMT is the ESRI Shapefile [ESRI98] that can be imported within the QGIS software using the default add data functionality, or layers may be created on-the-fly within the OpenQuake IRMT using GEM socio-economic databases. A QGIS project can include multiple layers that can be utilized to provide the variables and maps necessary for an integrated risk assessment.

In seismic hazard and risk analysis, a Ground-Motion Measure Type (GMMT) is a physical quantity expressing a particular characteristic of the ground shaking recorded or computed at one site. The most important and frequently used GMMTs are scalar and they indicate the shaking intensity (i.e. the amplitude of the ground shaking). These GMMT are also indicated with the acronym IMT. Other ground-motion measures define, for example, the duration of the shaking. A very common IMT is the peak ground acceleration, specified with the PGA acronym. The principal IMT used in the OpenQuake-engine are:

  • Peak Ground Acceleration – indicated as PGA – measured in fractions of g

  • Peak Ground Velocity – indicated as PGV – measured in cm/s

  • Peak Ground Displacement – indicated as PGV – measured in cm

  • Spectral Acceleration for a given period T – indicated as Sa(T) - measured in fractions of g

An Intensity Measure Level (IML) is a value of a specific IMT.

[ESRI98]

ESRI Shapefile Technical Description, Environmental Systems Research Institute, Redlands, C.A.