Very Precise Dating of Prehistoric Earthquakes in Southern California Using Tree-ring Analysis

本文建议沿圣安德烈亚斯断层继续取样，以寻找更多受地震干扰的古树。这些受干扰的树木可以提供史前地震事件的时间和程度的信息，因为它们的年轮记录可以确定日期并被破译。先前的树木年轮样本和来自该项目第一部分的新样本证实了1857年地震对南加州某些树木的影响。沿着卡洪山口西北10公里长的圣安德烈亚斯断层采集的样本显示，1812年和1813年的生长季节之间存在强烈的扰动。据报道，1812年的一次大地震鼓励了这样一种解释，即树木年轮数据可以确定地震的位置，而地震的位置在时间上是已知的，但在空间上是未知的。由于1812年（12月）和1857年（1月）之间的44年间隔，比以前估计的沿此段的复发间隔短得多，因此将在该地区进行进一步的抽样和研究。准确描述1812年末的破裂程度将是本研究的主要重点。研究还将继续对圣安德烈亚斯断层其他部分的样本进行研究。在有限的时间内，北加州将继续努力。那里的注意力将集中在1838年湾区事件的程度上。

It is proposed herein to continue sampling along the San Andreas fault in order to find more old-aged trees that have been disturbed by earthquakes. These disturbed trees can provide information about timing and extent of prehistoric earthquake events as their records of annual growth rings are dated and deciphered. Previous tree-ring ssampling and new samples from the first supported part of this project confirm the effects of the 1857 earthquake in certain trees in southern California. Samples along a 10 km length of the San Andreas fault just northwest of Cajon Pass show evidence of strong disturbance between the growing seasons of 1812 and 1813. A reported great earthquake in 1812 encourages the interpretation that tree-ring data can define the location of this earthquake, which is known in time but not in space. Further sampling and study will ensue in this area, because the interval of only 44 years, between 1812 (December) and 1857 (January), is much shorter than previous estimated recurrence intervals along this segment. Precise delineation of extent of rupture in late 1812 will be the primary focus of this research. Studies will also continue on samples from other segments of the San Andreas fault. Within constraints of time, efforts will continue in northern California. The concentration there will be on the extent of the 1838 event in the Bay Area region.