Dates of the Two Most Recent Surface Ruptures on the Southernmost San Andreas Fault Recalculated by Precise Dating of Lake Cahuilla Dry Periods
Dates of the Two Most Recent Surface Ruptures on the Southernmost San Andreas Fault Recalculated by Precise Dating of Lake Cahuilla Dry Periods
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通过卡韦拉湖干旱期的精确测年重新计算最南端圣安德烈亚斯断层最近两次表面破裂的日期
DOI：
10.1785/0120170392
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发表时间：
2018
影响因子：
3
通讯作者：
Erik C. Haaker
中科院分区：
文献类型：
--
作者：
T. Rockwell;A. Meltzner;Erik C. Haaker
过去两次最南端的圣安德烈亚斯断层（SAF）破裂发生在古卡维拉斯湖满水时，这是基于断层湖沉积关系和海岸线附近地点的广泛液化。过去两次南部 SAF 地震破裂的时间已经通过过去三个卡维拉湖高位之间的原位树桩的新放射性碳数据进行了重新评估，这些数据与历史记录和湖泊充水和干燥时间的建模相结合，为过去两次 SAF 地震提供了更精确的年龄。内环和外环上的 C 日期结合历史观测表明，最后一个湖泊之前的干旱期在公元 1706 年之后结束，留下了一个不到 25 年的狭窄窗口来填充并开始干燥最近的湖泊，而倒数第二个湖泊在公元 1640 年左右或更早开始从高位下降。我们的分析表明，最近一次地震发生在公元 1726 年 7 年左右，而倒数第二次地震的发生时间稍早，为公元 1577 年 67 年（均为 2σ）。这些新日期与先前对南部 SAF 事件的年龄估计相结合，表明地表破裂事件的复发更加频繁，平均间隔约为 180 年，但开放间隔为近 300 年。
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 C 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 7 C.E., whereas the timing of the penultimate event is slightly older at 1577 67 C.E. (both at 2σ). 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.