Collaborative Research: Targeting the Phase III SAFOD Drilling

0454511 Thurber圣安德烈亚斯断层深度观测站（SAFOD）项目的一个关键目标是钻穿一个小型重复地震的破裂补丁。破裂斑的大小约为几十米;因此，以相当的准确度知道它的位置对SAFOD的成功至关重要。我们正在进行的工作对SAFOD钻探的最后阶段至关重要，需要达到目标地震的定位精度约为10米。我们正在通过利用将在第二阶段钻井结束时安装的钻孔串来完成这一任务，该钻孔串将使地震传感器非常接近目标区域（约100米）。然后，我们将启动6杆约50-100磅。在我们的临时阵列、SAFOD先导孔中的钻孔串和第二阶段SAFOD钻孔串同时记录的约9至12个月期间，在临时地震记录点附近。由此产生的主动和被动数据集将为校准和改进地震波速模型提供有力的手段，使我们能够达到第三阶段钻井所需的10米精度。最后，我们将继续分析第三阶段钻井完成后收集的数据，以完善和扩展我们的圣安德烈亚斯断层带结构模型。

0454511ThurberA key objective of the San Andreas Fault Observatory at Depth (SAFOD) project is to drill through the rupture patch of a small repeating earthquake. The size of the rupture patch is on the order of tens of meters; hence knowing its location to a comparable degree of accuracy is vital to SAFOD's success. The work we are carrying out is critical to this final phase of SAFOD drilling, and requires reaching a level of location accuracy for the target earthquakes of about 10 meters. We are approaching this task by taking advantage of a borehole string, to be installed at the end of Phase II drilling, that will bring earthquake sensors very close (~100 m) to the target zone. We will then set off 6 shots of about 50-100 lbs. near temporary earthquake recording sites during a ~9 to 12 month period of concurrent recording by our temporary array, a borehole string in the SAFOD Pilot Hole, and the Phase II SAFOD borehole string. The resulting combined active and passive data set will provide a potent means for calibrating and improving the seismic wavespeed models that will enable us to achieve the 10 m accuracy required for the Phase III drilling. Finally, we will continue to analyze data collected after Phase III drilling is completed in order to refine and extend our models of San Andreas fault zone structure.