OpenQuake_gmfs

GROUND MOTION FIELDS USING OPENQUAKE

This folder includes the OpenQuake input files to generate scenario ground motion fields (gmfs) considering different sources of information:

1. From rupture.
2. From rupture and conditioned to recording stations (with only seismic stations or with seismic and macroseismic stations).
3. From ShakeMap.

The following files are available:

• stationlist_seismic.csv: OpenQuake input file with past observations, considering only seismic stations. If no seismic stations are available for the event, the file is not reported.
• stationlist_all.csv: OpenQuake input file with past observations, considering seismic and macroseismic stations. If no macroseismic stations are available for the event, the file is not reported.
• site_model_stations.csv: OpenQuake input file with the site model (Vs30 values) at the location of the observations.
• site_model.csv: OpenQuake input file with the site model for which the ground shaking will be estimated.
• site_model.png: Figure of the site model (Vs30 based on USGS data).
• gmpe_logic_tree_*.xml: OpenQuake input file with a ground motion model logic tree (gmlt).
• job_stations_none.ini: A configuration file (job.ini) for running OpenQuake scenario calculations without conditioning the ground shaking to given observations.
• job_stations.ini: A configuration file (job.ini) for running OpenQuake calculations when conditioning the ground shaking to given observations.

NOTE: the configuration files are examples for a given rupture geometry and a given gmlt. These parameters can be adjusted to the preferred models.

Median ground motion fields

The following images present the median ground motion field for the combination of rupture and GMPE that generates the lowest nominal bias when conditioning the ground shaking to observations. The folder Sensitivity provides the summary of the sensitivity analysis carried out with the available ruptures and GMPEs.

Sensitivity analysis

The following information is available in the Sensitivity folder :

• calculation_summary.csv: Details on the calculations carried out in the sensitivity analysis.
• log_calc_*.txt: File with the OpenQuake running information in a .txt format. This file includes the nominal bias estimates for each GMPE present in the logic tree model.
• gmf_median_PGA_*.csv: Generated ground motion fields for PGA for a given calculation ID.

Metadata in file calculation_summary.csv

• calc_id: unique identifier for the calculation.
• description: details on the calculation
• cal_time: time of the calculation.
• recording_stations: "All" stations (seismic + macroseismic), or only "seismic" stations.
• gmlt: Ground Motion Logic Tree used in the calculation.
• rupture: Rupture model used in the calculation.
• gmpe: Ground Motion Prediction Equation (ground motion model).
• imt: Intensity measure type.
• max_gmv: Maximum ground motion value.
• nominal_bias_mean: A single value useful as a measure of the event bias for a given gmpe. It refers to the mean of the between-event residuals after conditioning the shaking to the recording stations.
• nominal_bias_stdev: Standard deviation for the nominal_bias_mean.
• abs_bias: Absolute value of the nominal_bias_mean.

To run an OpenQuake calculation

1. From Rupture

Start a calculation from a given rupture in OpenQuake xml format and combine it with a logic tree for the applicable GMPEs (ground motion prediction equations):

rupture + gmpe_logic_tree + job_stations_none.ini

2. From Rupture and conditional to recording stations

Condition the ground motion fields based on the recording stations available for the event (stationlist.csv files). In this case, the calculation uses a given rupture in OpenQuake xml format, the observed values in the recording stations, and a given ground motion model.

The conditioning of the ground motion can consider:

• The recording stations with only seismic stations.
• All recording stations (with seismic and macroseismic values).

rupture + gmpe_logic_tree + stationlist_seismic.csv + job_stations_seismic.ini
rupture + gmpe_logic_tree + stationlist_all.csv + job_stations_all.ini

3. From Shakemap

The gmfs computed from the USGS ShakeMap can be generated with the command

oq shakemap2gmfs {shakemap_id} {sites.csv} -n 0 -s 0 -t 0 --spatialcorr yes -c yes

example of shakemap_id: us2000ar20 

It is possible to specify the number of ground motion fields, the truncation level, the spatial correlation, and the cross-correlation.

In OpenQuake, it is also possible to run scenario risk calculations starting from the USGS ShakeMap.