4D stress evolution models of the San Andreas Fault System using improved geodetic and paleoseismic constraints

Bridget R. Smith-Konter, Karen M. Luttrell, Xiaopeng Tong, & David T. Sandwell

Published August 12, 2016, SCEC Contribution #6686, 2016 SCEC Annual Meeting Poster #010

Major earthquakes of the San Andreas Fault System (SAFS) are thought to occur when accumulated fault stress in the upper locked portion of the crust exceeds some threshold value. 4D simulations of stress evolution provide rare insight into earthquake cycle crustal stress variations at seismogenic depths where earthquake ruptures nucleate, however we emphasize two important details: 1) modeled stress accumulation through time is largely prescribed by the assumed slip history, and thus these results highlight the need for continual improvements to and utilization of contemporary paleoseismic chronologies; 2) improved resolution and accuracy of the near-fault velocity field using new, integrated GPS and InSAR data is critical for improving strain and stress rate models of the SAFS, particularly in areas where the GPS array spacing is inadequate for resolving small variations in locking depth. Utilizing new SCEC community paleoseismic and geodetic data, our refined stress models are used to explore the temporally and spatially varying stress threshold conditions, and the sensitivity of these results, for major segments of the SAFS. 4D models demonstrate complex stress accumulation and stress drop behaviors as functions of space and time, with pockets of stress concentrated at depth due to the interaction of neighboring fault segments and at fault segment branching junctions. Because stress drops of major strike-slip earthquakes rarely exceed 10 MPa, these models may provide a lower bound on estimates of stress evolution throughout the historical era, and perhaps an upper bound on the expected recurrence interval of a particular fault segment. Moreover, these 4D visualizations lay the groundwork for 4D time-series animations, an important step forward in simulating stress evolution over multiple earthquake cycles spanning paleoseismic timescales.

Citation
Smith-Konter, B. R., Luttrell, K. M., Tong, X., & Sandwell, D. T. (2016, 08). 4D stress evolution models of the San Andreas Fault System using improved geodetic and paleoseismic constraints. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)