SCEC Award Number 13043 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Incorporating Roughness and Supershear in UCSB Broadband Modeling
Investigator(s)
Name Organization
Ralph Archuleta University of California, Santa Barbara
Other Participants Jorge Crempien
Daniel Lavallee
SCEC Priorities 6, 3, 4 SCEC Groups GMSV, GMP, CS
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 In this report we show one- and two-point statistic results of rupture velocity obtained from 2D dynamic rupture simulations on rough faults. We also find that there is no great variation in rupture time along the multiple dynamic rupture simulations, contrary to the hypothesis of Gusev (2012). These results have been tested and incorporated into the UCSB broadband ground motion code as an option to simulate kinematic source descriptions of earthquake ruptures on faults.
Intellectual Merit We use the 2D rough fault simulations of Dunham (2011) and Trugman & Dunham (2014). From these simulations we computed one- and two-point statistics for all rupture simulations combined for rupture velocity. We also looked at the difference between rupture time and a smoothed curve with a running mean to probe if there are large deviations from the mean in rupture time, as proposed by Gusev (2012). A histogram of the time difference between the smoothed model and the actual rupture time is shown in Figure 5. We find a mean value ~0.034 s for the log absolute difference between smoothed and original data. This difference —basically the difference between the time derived from a constant rupture velocity and the actual time of rupture— is small. Gusev (2012) hypothesized time differences that can be on the order of a second or fractions of a second that lead to discontinuous jumps in the rupture times. These results have been tested and incorporated into the UCSB broadband ground motion code as an option to simulate kinematic source descriptions of earthquake ruptures on faults.
Broader Impacts This research has partially supported one graduate student and gave very limited support to a soft-money researcher. This research is an integral part of UCSB's kinematic simulations of broadband strong ground motion. The variation in rupture velocity can contribute significantly to high-frequency ground motions. This research provides a physics based rationale for including variations in rupture velocity in the kinematic simulations of ground motion.
Exemplary Figure Figure 5.
Histogram of the log absolute value of the difference between rupture time and smoothed rupture time using a running mean smoother.