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Dates of the two most Recent surface ruptures on the southernmost San Andreas Fault recalculated by precise dating of Lake Cahuilla dry periods

Thomas K. Rockwell, Aron J. Meltzner and Erik C. Haaker
Dates of the two most Recent surface ruptures on the southernmost San Andreas Fault recalculated by precise dating of Lake Cahuilla dry periods
Bulletin of the Seismological Society of America (June 2018) 108 (5A): 2634-2649

Abstract

The past two southernmost San Andreas fault (SAF) ruptures occurred when ancient Lake Cahuilla was full, based on faulted lake sediment relationships and extensive liquefaction at sites near the shoreline. The times of the past two southern SAF ruptures have been reevaluated with new radiocarbon data on in situ stumps that grew between the past three Lake Cahuilla highstands, which, when taken in combination with historical accounts and modeling of the time to fill and desiccate the lake, provide more precise and accurate ages for the past two SAF earthquakes. The C14 dates on inner and outer rings combined with historical observations show that the dry period prior to the last lake ended after 1706 C.E., leaving a narrow window of less than 25 yrs to fill and begin desiccating the most recent lake, and that the penultimate lake began dropping from a highstand around 1640 C.E. or earlier. Our analysis shows that the most recent earthquake occurred about 1726+ or -7 C.E., whereas the timing of the penultimate event is slightly older at 1577+ or -67 C.E. (both at 2sigma ). These new dates, when combined with previous age estimates of earlier southern SAF events, suggest more regular recurrence of surface-rupturing events, with an average interval of about 180 yrs, but leave the open interval at nearly 300 yrs.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 108
Serial Issue: 5A
Title: Dates of the two most Recent surface ruptures on the southernmost San Andreas Fault recalculated by precise dating of Lake Cahuilla dry periods
Affiliation: San Diego State Universty, Department of Geological Sciences, San Diego, CA, United States
Pages: 2634-2649
Published: 20180626
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
Accession Number: 2018-057708
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
N32°30'00" - N42°00'00", W124°30'00" - W114°15'00"
Secondary Affiliation: Nanyang Technological University, SGP, SingaporeG3SoilWorks, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201831
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