RAPID: Fault Creep Following the Mw=7.2 Sierra El Mayor Earthquake of 4 April

调查的目标是迅速部署对加利福尼亚州南部和墨西哥北部断层运动敏感的仪器。这些断层都位于2010年4月4日发生的Mw=7.2的塞拉利昂市长地震的震中以北，那次地震突然增加了南加州的构造应力，使美国的三个主要断层系统接近崩溃：埃尔西诺、圣哈辛托和圣安德烈亚斯系统。地震学家认为，在一次或多次大于7兆瓦的地震中，这些系统内的断层段可能会滑动，给美国造成巨大的经济损失。在最近的地震之前，至少有两个管段已经濒临崩溃。这三个断层系统的表面痕迹都有轻微的滑动(通过触发的蠕变过程)，以响应4月地震释放的瞬时应力。一些人继续蠕动，对余震和主震期间的瞬时应力做出反应。问题是，这三个断层系统中哪一个最有可能在未来的地震中经历故障，目前正在进行几次遥感和当地测量，以确定目前发生的最显著的应力变化。目前正在安装的仪器(地震后不到一周开始)由六根埋在地下的20‘到60’长的石墨棒组成，这些石墨棒倾斜地安装在每个断层上，并牢牢地固定在一侧的岩石上，如果断层移动，这些石墨棒将通过伸缩的塑料管拉出。位移传感器监测杆的自由端相对于断层远端第二锚的位移，精度为1/1000英寸。位移每15分钟测量一次，并由本地数据记录器记录，该记录器从AA小区自主运行长达一年。这些数据每两小时通过一部手机传输到一个可公开访问的网站，科学界、运输和管道当局以及公众都可以在那里查看这些数据。如果这些被监测的断层中的任何一个发生异常地震滑动，可以通过远程命令将延迟减少到1分钟以下。在这种情况下，地震界将处于知情的地位，就地震后生命线中断的危险增加向公众提供建议，远远快于公众或地质学家检查震中的时间。该网站为https://datagarrison.com/用户名=Geo，密码为Hobo。

The investigation has as its objective the rapid deployment of instruments sensitive to the movement of faults of southern California and northern Mexico. These faults all lie to the north of the epicenter of the Mw=7.2 Sierra Mayor earthquake of 4 April 2010, which abruptly increased tectonic stress in southern California, bringing three major US fault-systems closer to failure: the Elsinore, San Jacinto and San Andreas systems. Seismologists believe that fault segments within each of these systems could slip in one or more earthquakes greater than Mw=7 resulting in huge economic losses in the US. At least two of segments were already close to failure prior to the recent earthquake. The surface traces of segments of these three fault systems all slipped a minor amount (by a process of triggered creep) in response to the instantaneous stress released by the April earthquake. and some continue to creep in response both to aftershocks, and to the instantaneous stress during the mainshock. The question arises as to which of these three fault systems is most likely to experience failure in a future earthquake, and several remote sensing and local measurements are being undertaken to identify the most significant stress changes that have now occurred.The instrumentation being installed by the present project (starting less than a week after the earthquake) consists of six buried 20' to 60'-long graphite rods installed obliquely across each fault, and attached firmly to the rock on one side, that are drawn through a telescopic plastic pipe should the fault move. A displacement transducer monitors the displacement of the free end of the rod relative to a second anchor on the remote side of the fault to an accuracy of 1/1000 inch. The displacement is measured every 15 minutes and recorded by a local data logger that operates autonomously from AA cells for up to a year. The data are transmitted through a cell phone every 2 hours to a publicly accessible web site where they may be viewed by the scientific community, by transportation and pipeline authorities, and by members of the public. The latency can be decreased to less than 1 minute by remote command, should anomalous seismic slip occur on any of these monitored faults. In such an event the seismological community will be in an informed position to advise the public concerning increased hazards to lifeline interruptions following an earthquake, far sooner than it takes for members of the public or geologists to inspect the epicenter. The website is https://datagarrison.com/ user=geo, password hobo.