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Published August 2004 | Published
Journal Article Open

The Tejon Pass Earthquake of 22 October 1916: An M 5.6 Event on the Lockwood Valley and San Andreas Faults, Southern California

Abstract

On 22 October 1916, a moderate earthquake occurred in the vicinity of Tejon Pass and was felt over much of southern California. An intriguing aspect of this event involves reports of ground cracks that formed during the earthquake. We evaluate the reports of ground cracking and attempt to precisely locate the cracks with respect to active faults; we infer that the earthquake produced minor fault rupture along a newly discovered trace of the easternmost Lockwood Valley fault (formerly mapped as the easternmost Big Pine fault) and/or along the San Andreas fault. We also re-evaluate and present new intensity data, and we use a grid-search algorithm (derived from empirical analysis of modern earthquakes) to find the magnitude most consistent with the reported intensities. Although previous authors have attempted to use intensity data to constrain the magnitude of this event, the algorithm we use provides an alternative and statistically more robust determination of the magnitude. Our results suggest M 5.6 (-0.3/+0.2) (at 95% confidence) for the 1916 event, which is consistent with earlier work. The 1916 earthquake appears to have been a rare and remarkable event in terms of its size and location and the production of minor surface rupture.

Additional Information

© 2004 Seismological Society of America. Manuscript received 29 September 2003. We thank Tousson Toppozada for a helpful review of an early version of this article, and we thank Mike Rymer and an anonymous reviewer for thoughtful suggestions which led to substantial improvements and new findings. Our work benefited significantly from insightful discussions with Karl Kellogg, and we are very grateful for his assistance. We also wish to express our tremendous thanks to Marty Morehart, for providing access to Cuddy Ranch and for sharing his knowledge, and to Eloise Richer, Ann Wride, and the volunteers of the Ridge Route Communities Historical Society and Museum for sharing their knowledge and offering their assistance (and simply for their ongoing efforts to preserve the breadth of knowledge of local history). We wish to acknowledge the use of the Generic Mapping Tools software package by Wessel and Smith (1991) to generate parts of Figures 1, 2, and 5 in this report.

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August 19, 2023
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October 26, 2023