Seismic Source Module

The seismic source module contains instructions and workflows for evaluating models related to seismic sources.

This section outlines how to utilize the Event-Based PSHA calculator in the OpenQuake Engine specifically to generate Stochastic Event Set (SES)—synthetic catalogues of earthquake ruptures.

Understanding Event-Based PSHA

Stochastic Event Set (SES) is a potential realization of the seismicity (i.e. a list of ruptures) produced by the source model over the investigation time for the hazard calculation. The Event-Based PSHA calculator utilizes Monte Carlo sampling [16] to generate the SES.

While the standard Event-Based PSHA calculator computes and stores stochastic event sets and the corresponding Ground-Motion Field (GMF) (often producing hazard curves and hazard maps similar to the Classical PSHA calculator), this module focuses only on the source generation phase. The computed synthetic catalogues are incredibly valuable for source modeling and can be used directly for comparisons against a real catalogue to validate the seismicity rate and rupture geometries.

For more detailed information to Event-Based PSHA, please refer to Pagani et al., (2014) [17] and OpenQuake Engine Documentation.

Generating Stochastic Event Sets (SES)

To generate an SES without computing the subsequent hazard (Ground-Motion Field (GMF)), we only need to configure the OpenQuake Engine to sample the source logic tree and generate the temporal and spatial distribution of ruptures.

Inputs

All required input files for the event-based calculation is placed within data/event_based_PSHA/ folder. Typically, this includes:

Seismic Source Model XML file (it_example.xml).
Source Logic Tree XML file (source_model_logic_tree.xml).
Main configuration file (job.ini).

You can find more detailed information for inputs in the OpenQuake Engine Documentation.

Note

Because we are exclusively generating earthquake ruptures and skipping the hazard calculation, you do not need to provide a Ground Motion Logic Tree (GMM) file or define site models. But we keep them in the data folder in case you wish to perform full event-based PSHA.

Simulation phase

After you prepare the necessary input files of event-based PSHA, you can run the analysis and see outputs using your terminal (optional). To do these, there is a plenty of ways based on how you use OpenQuake engine. You might see the Running Calculations section for running calculations options and more detailed information.

Outputs

At the end of an event-based calculation configured purely for Stochastic Event Sets generation, the OpenQuake engine will output the generated Stochastic Event Sets. The list of outputs can be seen using the oq engine --lo <calculation ID> command. In addition, you can export all the results of a given calculation using the oq engine --eos <calculation ID> tmp for further post-processing and comparison against your real catalogues.

Note

In the tutorial section below, you might find how to generate a stochastic event set from an OQ Engine area source with known geometry (i.e. a polygon in a shapefile or geojson), a magnitude-frequency distribution (MFD), and a hypocentral depth distribution (optionally specified by means of an OQ Engine probability mass function).