Elastic and Inelastic Responses of Compliant Fault Zones to Nearby Earthquakes in Three Dimensions: a parameter-space study

Jingqian Kang, & Benchun Duan

Published 2015, SCEC Contribution #1955

Using dynamic rupture models of a right-lateral fault embedded in an elastic or elastoplastic 3D medium, we investigate elastic and inelastic responses of compliant fault zones to nearby earthquake ruptures. We particularly examine effects of fault depth, width, shape, and rigidity reduction on the surface displacement field. Our results from elastic models show that deeper and wider fault zones generally result in larger residual displacements. However, for shallow fault zones, the vertical residual displacement is insensitive to or even decreases with fault zone width. The width of horizontal displacement anomalies across a fault zone is only indicative of the fault zone width near the Earth’s surface. There are trade-off effects among fault zone depth, width, shape and rigidity reduction on the amplitude of surface residual displacements. Plastic strain can occur along the entire fault zone near the Earth's surface and in the extensional quadrant at depth, if fault zone rocks are close to failure before a nearby earthquake. Compared with results from elastic models, plastic strain near the Earth's surface generally enhances surface displacements of a fault zone and does not change the trend of effects of fault zone depth and width, while plastic strain at depth can result in reduced retrograde motion or sympathetic motion across the fault zone and introduce complexities in effects of fault zone depth and width. Sympathetic horizontal motion more likely occurs across a narrow fault zone with inelastic response at depth. Vertical motion in the extensional quadrant may actually decrease with fault zone width in plastic models. Sympathetic horizontal motion, or small retrograde horizontal motion in conjunction with large vertical motion above a fault zone are indicatives of inelastic response of the fault zone at depth.

Citation
Kang, J., & Duan, B. (2015). Elastic and Inelastic Responses of Compliant Fault Zones to Nearby Earthquakes in Three Dimensions: a parameter-space study. Geophysical Journal International, 201, 1193-1212.