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

这里建议继续沿着圣安德烈亚斯断层进行采样，以发现更多受到地震干扰的老树。这些受干扰的树木可以提供有关史前地震事件的时间和程度的信息，因为它们的年轮记录被确定了日期和解密。之前的树木年轮采样和来自该项目第一个支持部分的新样本证实了1857年地震对南加州某些树木的影响。沿着圣安德烈亚斯断层10公里长的样品，就在卡洪山口西北部，显示出1812年和1813年生长季节之间强烈干扰的证据。1812年报道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这次地震的位置，这在时间上是已知的，但在空间上是不知道的。随后将在这一地区进行进一步的采样和研究，因为在1812年(12月)至1857年(1月)之间只有44年的间隔，比这一段以前估计的重现间隔要短得多。1812年末断裂程度的精确圈定将是这项研究的主要焦点。对圣安德烈亚斯断层其他部分的样本的研究也将继续进行。在有限的时间内，加州北部的努力将继续下去。那里的注意力将集中在1838年事件在湾区的范围上。

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.