Preferred Rupture Directivity in Hazard Curve Computations

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This page documents efforts to investigate the impact that preferred rupture directions would have on hazard as calculated with CyberShake ground motions in OpenSHA.

Research Plan

There is some evidence that some faults have a preferred rupture direction. To investigate the impact this could have on hazard, we'll identify a handful of faults, modify the probabilities of individual rupture variations to favor those at the preferred end of the fault, and generate new hazard products with the modified probabilities. No new ground motions will need to be calculated; we'll use Study 22.12 and 24.8 ground motions.

Below is a flow chart representing the steps involved in performing this work.

Preferred Rupture Direction flow chart.png

Implementation Details

With the UCERF2 ERF used in Study 22.12 and Study 24.8, probabilities are specified at the rupture level -- that is, for a specific fault segment(s) and magnitude. We then divide the probability by the number of rupture variations to get the uniform probability of each rupture variation. For this work, we will create modified rupture variation probabilities and use these to generate a modified hazard curve.

We will add new functionality to the CyberShake-related code in OpenSHA to support this work. OpenSHA has a defined interface to return a list of probabilities for a given source ID and rupture ID. We'll specify the source ID, rupture ID, rupture variation ID, probability in a CSV file which will be passed to OpenSHA. This file will be parsed and used to populate a data structure, which will then be accessed by an implementation of the interface to determine the new probabilities. For any source ID, rupture ID, rupture variation ID combinations not in the file, we'll use the default UCERF2 probabilities. Then the new probabilities will be used to create a hazard curve.

Modifying the HazardCurvePlotter to allow us to input custom probabilities for rupture variations allows us to compare hazard expected for persistent directivity vs random rupture direction. We can prescribe directivity based on topography or physics reasons and see if the signature is drowned out by randomness of the network or if it still stands out.


New Functionality

The existing OpenSHA command-line tool, HazardCurvePlotter, is able to compute hazard curves and plot them to images locally on a system. We’ve added a new parameter, rv-probs-csv, for a Rupture Variation Probabilities Input CSV file.

Passing this file allows a user to specify directivity for specific rupture variations. Previously, all variations had an equal probability, distributed from the probability of the rupture itself. The sum of probabilities of the variations must still sum to the probability of the corresponding rupture.

CSV Files

CSV Structure

The input CSV file should have the following columns.

  • Source_ID
  • Rupture_ID
  • Rup_Var_ID
  • Probability

The specified source and rupture acts as a composite key, uniquely identifying a rupture variation. Each rupture at a site is comprised of a set of rupture variations. The CSV file does not need to have an entry for each variation found in the CyberShake database. The remaining unspecified variations are given an equal probability distributed from the difference of the rupture probability and the sum of rupture variation probabilities specified. The formatting, structure, and sum or probabilities are validated in the HazardCurvePlotter.

CSV Generation

To generate the CSV files used for these tests, we created a Python script which takes in a configuration file and outputs a CSV with modified probabilities for selected rupture variations.

The Python script is available here.

Inputs

Here are the CSV files used so far.



Note: Due to the similar plots below, we believe more input CSVs with more variations across more ruptures will result in significantly different results. When modifying the probability of the rupture itself and removing precondition checks as necessary, we do see significant changes.

The commands utilizing these CSVs and the corresponding runs are found in the plots section below.

Plots

The following plots show curves for the following sites:

  • ALP
  • USC
  • SBSM
  • SVD
  • PDE

There is a plot for each site of the periods (K) 2, 3, 5, and 10, for a total of 20 plots. Each figure has the following plot lines

  • The reference using original probabilities (Ref)
  • Where hypocenters are responsible for 90% of the probability (90p)
  • USC and SBSM has additional plot line where hypocenters are responsible for 100% (100p)


For all of the 10p, 90p, and 100p plots, the results are identical to the fetched probabilities. We're continuing to find which modified directivity on which sites might result in significant ground motion impact. More CSVs will be generated and new plots added. For the sake of brevity, we won't show all 20 plots here.

The X,Y data points and all plots generated are available in the Excel spreadsheet : File:Hazard Curve Comparison Plots.xlsx


Comparison plots were made by copying out the TXT X,Y datapoints into Excel. We may expand existing OpenSHA Comparison Plot functionality for this purpose. Currently we're able to compare a new run against results fetched from a database, but not multiple modified plots.


USC 9306

USC 3s

Site: University of Southern California (USC)

Compute Time: 1.12 mins (90p), 48 seconds (100p)

Command Parameters:

--output-dir src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/modprob/90p/USC \

--run-id 9306 \

--component RotD50 \

--period 2,3,5,10 \

--rv-probs-csv src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/USC_mod_probs_Mojave_Coachella_90p.csv \

--plot-chars-file src/main/resources/org/opensha/sha/cybershake/conf/robPlot.xml \

--type TXT,PDF

--output-dir src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/modprob/100p/USC \

--run-id 9306 \

--component RotD50 \

--period 2,3,5,10 \

--rv-probs-csv src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/USC_mod_probs_Mojave_Coachella_100p.csv \

--plot-chars-file src/main/resources/org/opensha/sha/cybershake/conf/robPlot.xml \

--type TXT,PDF

ALP 9542

ALP 3s

Site: Antelope (ALP)

Compute Time: 1.28 mins

Command Parameters:

--output-dir src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/modprob/ALP  \

--run-id 9542 \

--component RotD50 \

--period 2,3,5,10 \

--rv-probs-csv src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/ALP_mod_probs_Mojave_Coachella_90p.csv \

--plot-chars-file src/main/resources/org/opensha/sha/cybershake/conf/robPlot.xml \

--type TXT,PDF

SBSM 9320

SBSM 3s

Site: San Bernardino Strong Motion (SBSM)

Compute Time: 59 seconds (90p), 1.02 mins (100p)

Command Parameters:

--output-dir src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/modprob/90p/SBSM  \

--run-id 9320 \

--component RotD50 \

--period 2,3,5,10 \

--rv-probs-csv src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/SBSM_mod_probs_Mojave_Coachella_90p.csv \

--plot-chars-file src/main/resources/org/opensha/sha/cybershake/conf/robPlot.xml \

--type TXT,PDF

--output-dir src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/modprob/100p/SBSM \

--run-id 9320 \

--component RotD50 \

--period 2,3,5,10 \

--rv-probs-csv src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/SBSM_mod_probs_Mojave_Coachella_100p.csv \

--plot-chars-file src/main/resources/org/opensha/sha/cybershake/conf/robPlot.xml \

--type TXT,PDF

SVD 9647

SVD 3s

Site: Seven Oaks Dam (SVD)

Compute Time: 1.28 mins (90p)

Command Parameters:

--output-dir src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/modprob/90p/SVD  \

--run-id 9647 \

--component RotD50 \

--period 2,3,5,10 \

--rv-probs-csv src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/SVD_mod_probs_Mojave_Coachella_90p.csv \

--plot-chars-file src/main/resources/org/opensha/sha/cybershake/conf/robPlot.xml \

--type TXT,PDF

PDE 9663

PDE 3s

Site: Pardee (PDE)

Compute Time: 1.35 mins (90p)

Command Parameters:

--output-dir src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/modprob/90p/PDE  \

--run-id 9663 \

--component RotD50 \

--period 2,3,5,10 \

--rv-probs-csv src/test/resources/org/opensha/sha/cybershake/plot/HazardCurvePlotter/PDE_mod_probs_Mojave_Coachella_90p.csv \

--plot-chars-file src/main/resources/org/opensha/sha/cybershake/conf/robPlot.xml \

--type TXT,PDF

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