SCEC Award Number 14058 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Bounding the Rate of Moment Deficit on Faults
Name Organization
Paul Segall Stanford University Kaj Johnson Indiana University
Other Participants Jeremy Maurer, Ph.D. student
SCEC Priorities 1d, 1e SCEC Groups WGCEP, Geodesy, Transient Detection
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
Forecasts of future ruptures are based on the brief historical record, paleoseismology, and geodetic strain accumulation. While we can never know the slip rate at every point on all faults in southern California, we can bound the moment deficit rate (MDR), or the integral of the slip deficit over each fault segment or fault system. In the past year we carefully tested a number of proposed methods for bounding the MDR using synthetic data and now we apply these methods to the faults system of Southern California and evaluate their performance. Preliminary results indicate that over the last 150 years, the accumulated seismic moment well exceeds that in the 1857 earthquake and is nearly that plus an additional M8 event.
Intellectual Merit Our project accomplishes something new in that we place defensible bounds on the rate that seismic moment deficit rate accumulates. The moment deficit rate loosely measures the rate of strain energy accumulation and when integrated over the last 150 years, is presumed to bound the seismic moment that could occur in the near future. Strain based estimates of seismic hazard complement those based on paleoseismology.
Broader Impacts In terms of broader impacts this project has contributed to the training of Ph.D. student Jeremy Maurer.
Exemplary Figure Figure 4. Constrained Optimization Bounding (COB) estimate of the total MDR for Southern California using a block model geometry. Black curve - pdf from COB assuming only East-North correlations in GPS data. Red curver - pdf from COB using empirically derived GPS covariance including interstation correlation (see text). Horizontal bars are estimates of the MDR from previous studies; the blue bars are Kostrov summation estimates; the solid line is Ward (1994) and Savage and Simpson (1997) and the dashed is Ward (1998). Green bars are from UCERF3; solid line is three different kinematic models and dashed line is an estimate using the geologic slip rates and assuming a fixed locking depth of 15 km everywhere. The black square is Meade and Hager (2005). Red squares are from Johnson (2013b); the solid square is a long-term-rigid elastic block model, J2 is an elastic plate-block model and equivalent to the block model results given by this study. The open square is a plate-block kinematic model and the crossed square is a viscoelastic cycle plate-block model. Vertical dashed black lines show the total moment released seismically since 1857 and total moment release plus an additional magnitude 8 event. The equivalent earthquake magnitudes shown assume all the moment deficit on all the faults is released at the same time.