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Introduction to the Special Section on the 2019 Ridgecrest, California, Earthquake Sequence

Hough, Susan E. and Ross, Zachary E. and Dawson, Timothy E. (2020) Introduction to the Special Section on the 2019 Ridgecrest, California, Earthquake Sequence. Bulletin of the Seismological Society of America, 110 (4). pp. 1395-1399. ISSN 0037-1106. doi:10.1785/0120200201.

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Following the 16 October 1999 M_w 7.1 Hector Mine earthquake, no earthquake larger than magnitude 6.0 occurred in southern California for nearly 20 yr. That lull came to an end with the occurrence of the 4 July 2019 M_w 6.4 earthquake at 22:40 UTC (10:33 a.m. local time). Located in a relatively sparsely populated part of the state, with most of its rupture within the China Lake Naval Air Weapons Station (NAWSCL) adjacent to the civilian town of Ridgecrest (population: 26,000), the earthquake was felt widely across most of southern California. Immediate response efforts were mounted to investigate the rupture and assess damage (Stewart et al., 2019) and to calculate aftershock probabilities (see Hardebeck, 2020; also see Data and Resources). The earthquake occurred in a region historically characterized by higher than average aftershock productivity (Hardebeck et al., 2019), leading to a higher‐than‐average probabilities for both large aftershocks and subsequent larger events. The latter odds, although still small, were borne out with the occurrence of 6 July M_w 7.1 earthquake at 03:19:53 UTC (8:19:53 p.m. local time on 5 July) ∼34  hr after the initial M_w 6.4. Arguably, the M_w 7.1 could be considered an aftershock, but, by convention, this earthquake is regarded as the mainshock, whereas the initial M_w 6.4 is considered a foreshock.

Item Type:Article
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URLURL TypeDescription
Hough, Susan E.0000-0002-5980-2986
Ross, Zachary E.0000-0002-6343-8400
Additional Information:© 2020 Seismological Society of America. Manuscript received 3 June 2020; Published online 21 July 2020. This special section is being published barely over one year after the 2019 Ridgecrest sequence. The authors thank Sarah Minson, Thomas Pratt, Justin Rubinstein, Shane Detweiler, and Michael Diggles for constructive feedback on this article and the many individuals whose work made the publication of this issue possible under very tight timelines: article authors, reviewers, BSSA Editor‐In‐Chief Thomas Pratt, BSSA Associate Editors Ivan Wong and Nicola Litchfield, and article coordinator Betty Schiefelbein. The work presented in this volume would also not have been possible without the contributions and cooperation of countless individuals, including many from Ridgecrest, China Lake, and Trona, for whom the “sparsely populated region” is their home and for whom the sequence has been a portentous event. The authors dedicate this volume to them. Data and Resources: Basic information about the Ridgecrest earthquake can be found at and (both last accessed June 2020). The operational aftershock forecast continues to be updated and can be found online at (last accessed June 2020). The unpublished manuscript by Dawson, T. E., C. B. DuRoss, R. D. Gold, K. M. Scharer, D. J. Ponti, T. C. Ladinsky, S. E. K. Bennett, V. E. Langenheim, D. McPhillips, A. E. Morelan, et al. (2020). “Field‐based observations of surface ruptures associated with the 2019 Ridgecrest earthquake sequence, California” was submitted to Bull. Seismol. Soc. Am.
Group:Seismological Laboratory
Issue or Number:4
Record Number:CaltechAUTHORS:20200831-094721356
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Official Citation:Susan E. Hough, Zachary E. Ross, Timothy E. Dawson; Introduction to the Special Section on the 2019 Ridgecrest, California, Earthquake Sequence. Bulletin of the Seismological Society of America ; 110 (4): 1395–1399. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105161
Deposited By: Tony Diaz
Deposited On:08 Sep 2020 18:57
Last Modified:16 Nov 2021 18:40

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