RSQSim Rupture Ground Motion Comparisons

Broadband Platform Comparisons

This exercise uses the SCEC Broadband Platform to compute seismograms and calculate RotD50 spectra from RSQSim ruptures in a 1-D velocity structure. We then compute the RSQSim results with those from suites of kinematic rupture models with the same grid spacing, rupture surface, and hypocenter using the Graves & Pitarka (2015) rupture generator.

Implementation Notes

RSQsim ruptures can be on very complex surfaces, while the BBP requires a planar representation. For this comparison, we choose simple relatively planar ruptures on the Mojave section of the San Andreas, which should minimize these differences.

Also, Graves & Pitarka uses a regular grid, while the RSQSim models considered use a triangular mesh. I compute an effective grid spacing to use in RSQSim as the square root of the average area of all triangles included in the RSQSim rupture, so the sources in the GP kinematic ruptures will have the same area as the average RSQSim triangle.

Results

Spectra plot legend:

• Black, solid line: RSQSim
• Gray, solid line: Mean GP
• Green, area: 16-86% GP percentiles
• Gray, area: 2.5-97.5% GP percentiles
• Light gray, area: Min/max range across all GP simulations

Catalog/Rup	Spacing	Rupture Image	USC RotD50 Spectra	SBSM RotD50 Spectra
rundir2194_long Rupture 136704, M7.32 SAF Mojave, S-E hypocenter	RSQSim: 1.32 km^2 triangles GP: 1.16km x 1.16km square	M7.32	USC	San Bernardino
JG UCERF3 Million Elements Rupture 4099020, M7.35 SAF Mojave, S-E hypocenter	RSQSim: 0.23 km^2 triangles GP: 0.48km x 0.48km square	M7.35	USC	San Bernardino