Variations of stress parameters in the Southern California plate boundary around the South Central Transverse Ranges

Niloufar Abolfathian, Patricia Martínez-Garzón, & Yehuda Ben-Zion

Submitted March 1, 2020, SCEC Contribution #10053

We examine stress parameters in Southern California with a focus on the region near the South Central Transverse Ranges (SCTR), using a refined stress inversion methodology to 1981-2017 declustered and aftershocks focal mechanisms independently. Comparison between the associated stress parameters provides information on the local dominant loading. The estimated stress parameters are examined in relation to the regional stress regime and local loadings. Over the regional scale, the SHmax trends towards the NNE and the stress ratios vary from transtensional stress regime near the Eastern California Shear Zone (ECSZ), to shear stress near the SCTR, and towards transpression near the Western Transverse Ranges. Detailed analysis of stress parameters near the SCTR indicates deviations from the regional shear stress. The San Bernardino Mountain area shows SHmax direction towards NNW and transpressional stress components likely associated with the relative motion of the San Andreas Fault and ECSZ. The Cajon Pass and San Gorgonio Pass show transpressional stress regime near the bottom of the seismogenic zones likely associated with the elevated topography. In Crafton Hills, rotation of the principal stress plunges and SHmax direction and transtensional stress regime below ~10 km, along with lower estimated apparent friction coefficient suggest a weak fault possibly associated with deep creep. The results reveal effects of local loadings resolved by the performed multi-scale analysis. The study does not show significant temporal variations of stress variations near the SCTR from the average stress parameters in the analyzed 37 years.

Citation
Abolfathian, N., Martínez-Garzón , P., & Ben-Zion, Y. (2020). Variations of stress parameters in the Southern California plate boundary around the South Central Transverse Ranges. Journal of Geophyical Research, (submitted).