In Situ Measurements of the Mechanical Properties of Active Fault Zones

该提案要求资金支持便携式激光应变仪在南圣安德烈亚斯断层附近的持续运行，并与完全锚定的激光应变仪共存。调查人员原计划在1999年秋季撤出便携式仪器，但由于在过去6个月里观察到一些不寻常的应变事件，因此正在请求资金继续操作该仪器。首先，自1994年以来，观测到几次与以往应变记录不同的地震应变快速变化。第二，对1999年10月17日赫克托雷地震7.1级地震的震后反应进行了观测。这次地震在靠近应变仪的圣安德烈亚斯断层南端附近引发了一系列地震，引发了人们对该地区加速变形可能性的真正担忧。鉴于目前的活动水平，该仪器的持续运行很可能会发现更多此类事件。更好地了解这些事件发生的地点，也许是如何发生的，应该提供有关断层力学的重要信息，以及关于圣安德烈亚斯断层南端的行为：圣安德烈亚斯断层的一端，自上次大地震以来已经过去了最长的时间。

Agnew, Duncan CarrEAR-0001116This proposal requests funds to support the continued operation of a portable laser strainmeter adjacent to the southern San Andreas fault and co-located with a fully anchored laser strainmeter. The investigator had planned to pull out the portable instrument in the fall of 1999, but is requesting funds to continue to operate the instrument because over the last six months a number of unusual strain events have been observed. First, there has been observed several aseismic but rapid strain changes which are unlike the previous behavior of the strain record since 1994. Second, there has been observed the postseismic response to the Mw 7.1 Hector Mine earthquake of 17 October 1999. This earthquake triggered a swarm of earthquakes adjacent to the southern termination of the San Andreas fault, near the strainmeters, leading to genuine concern over the possibility of accelerating deformation in the area. Given the current level of activity, it is very likely that continued operation of this instrument will detect further such events. Understanding better where, and perhaps how, these events occur should provide important information on fault mechanics in general and about the behavior of the San Andreas fault at its southern end: one end of that segment of the San Andreas which has the longest elapsed time since the last large earthquake.