Precise Dating and Location of Prehistoric Earthquakes Using Tree-Ring Analysis

我们初步成功地确定了圣安德烈亚斯断层上以前未知的一次大地震的年代和位置，这是几年来广泛采样和分析的结果。最终产品是一个日历日期，它给出了该事件与1857年历史记录中的事件之间的确切间隔。地震的含义是，该地区的应变释放可能是周期性的，而不是周期性的。本文建议进一步将树木年轮测年应用于古地震学。树轮分析实际上是独一无二的，因为它能够绝对确定地震等扰乱现场的事件的日期。正是在检查扰动之前，每个年轮的绝对年龄使这项申请确定在我们的研究区域西北部靠近加利福尼亚州莱特伍德的地方是否有更早的事件；研究1838年湾区事件的范围；准确确定卡斯卡迪亚俯冲带东南端的小鲑鱼断层上的事件的日期；并调查意大利南部的一个地区，那里的条件似乎非常有希望在活跃的地震区定位未记录的地面破裂。我们从以前的研究中获得的知识，包括令人失望的知识，使我们能够有效地开展工作，并针对更好的区域进行分析。优化结果的另一个步骤是纳入熟悉或在拟议研究地区工作的地震学家。他们提供的背景信息有助于确定具体问题和解释任何结果的地震意义。

Our initial success in dating and locating a major earthquake, previously unknown, on the San Andreas fault was the result of extensive sampling and analysis over several years. The end product is a calendar date giving an exact interval between that event and an event in the historical record in 1857. The seismic implications are that strain release in the area may be episodic rather than periodic. It is herein proposed to further apply tree-ring dating to paleoseismology. Tree-ring analysis is virtually unique in being able to absolutely date site-disturbing events like earthquakes. It is the absolute dating of each and every annual ring prior to examination for disturbance that makes this application determine if there was an earlier event just to the northwest of our study area near Wrightwood, California; study the extent of the 1838 event in the Bay area; precisely date an event on the Little Salmon fault at the southeast end of the Cascadia Subduction zone; and to investigate an area in southern Italy where conditions seem very promising for locating undocumented ground ruptures in an active seismic region. The knowledge gained from our previous studies, including the disappointments, has equipped us to operate efficiently and to target better zones for analysis. Another step to optimize results is the inclusion of seismologists familiar with or working in the proposed study areas. The background information furnished by them aids in defining specific questions and in interpreting the seismic significance of any results.