Was the M_w 7.5 1952 Kern County, California, earthquake induced (or triggered)?
Several recent studies have presented evidence that significant induced earthquakes occurred in a number of oil-producing regions during the early and mid-twentieth century related to either production or wastewater injection. We consider whether the 21 July 1952 M_w 7.5 Kern County earthquake might have been induced by production in the Wheeler Ridge oil field. The mainshock, which was not preceded by any significant foreshocks, occurred 98 days after the initial production of oil in Eocene strata at depths reaching 3 km, within ~1 km of the White Wolf fault (WWF). Based on this spatial and temporal proximity, we explore a potential causal relationship between the earthquake and oil production. While production would have normally be expected to have reduced pore pressure, inhibiting failure on the WWF, we present an analytical model based on industry stratigraphic data and best estimates of parameters whereby an impermeable splay fault adjacent to the main WWF could plausibly have blocked direct pore pressure effects, allowing the poroelastic stress change associated with production to destabilize the WWF, promoting initial failure. This proof-of-concept model can also account for the 98-day delay between the onset of production and the earthquake. While the earthquake clearly released stored tectonic stress, any initial perturbation on or near a major fault system can trigger a larger rupture. Our proposed mechanism provides an explanation for why significant earthquakes are not commonly induced by production in proximity to major faults.
Additional Information© 2017 The Author(s). This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Received: 6 May 2017; Accepted: 21 July 2017; Published online: 2 October 2017. We thank Elizabeth Cochran, Art McGarr, Steve Hickman, Katherine Kendrick, Gail Atkinson, and two anonymous reviewers for their reviews of this manuscript. We also thank Mariano Garcia-Fernandez for his editorial stewardship of this journal, as well as his patience. Figures 1 and 3 are generated using GMT software (Wessel and Smith 1991). Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Published - 10.1007_s10950-017-9685-x.pdf
Supplemental Material - 10950_2017_9685_MOESM1_ESM.docx