The electrical conductivity structure between the transitional (near SAFOD) and locked (SE of Cholame) segments of the San Andreas Fault, including the source region of the non-volcanic tremors

圣安德烈亚斯断层的过渡段（SAFOD 附近）和锁定段（Cholame 东南部）之间的导电结构，包括非火山震源区

• 批准号: 65513361
• 负责人: Professor Dr. Oliver Ritter
• 金额: --
• 依托单位: Department 2: Geophysik
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2012-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/65513361?language=en
• 关键词: electrical; conductivity; structure; between; transitional

The DeepRoot magnetotelluric (MT) experiment near the San Andreas Fault (SAF) Observatory at Depth (SAFOD) revealed a steeply dipping upper crustal high electrical conductivity zone flanking the seismically defined SAF to the NE, widening into the lower crust where it appears to be connected to a broad anomaly in the upper mantle. Becken et al. (2007a) suggested that the high conductivity represents a deep-rooted channel for crustal and/or mantle fluid ascent. Deep (~20-40 km), non-volcanic seismic tremors (NVT) have only been observed in an area ~40 km SE of the SAFOD where they are thought to originate from oscillation of fluids. The presence or absence of NVT appears to coincide with the transition of the SAF from being locked (Cholame) to intermediate creep (SAFOD) and could reflect significant structural changes affecting the deep hydraulic system along this portion of the SAF which in turn could be detectable with MT. Here, we propose an experiment to image an entire segment of an active plate boundary with a network of MT stations, from the Pacific into the Great Valley, crossing the NVT region beneath the SAF near Cholame. These results are important for the site characterization of the SAFOD as along-strike variations of the conductivity structure may reflect deep structural changes controlling the still debated mechanical state of the SAF.

圣安德烈亚斯断层 (SAF) 深度观测站 (SAFOD) 附近的深根大地电磁 (MT) 实验揭示了一个陡峭倾斜的上地壳高电导率带，位于地震定义的 SAF 两侧至东北方向，并扩大到下地壳，似乎与上地幔的广泛异常相连。贝肯等人。 (2007a) 认为高电导率代表了地壳和/或地幔流体上升的深根通道。仅在 SAFOD 东南约 40 公里的区域观察到深部（约 20-40 公里）非火山地震颤动 (NVT)，据认为该震颤源自流体振荡。 NVT 的存在或不存在似乎与 SAF 从锁定 (Cholame) 到中间蠕变 (SAFOD) 的转变一致，并且可以反映影响沿 SAF 这部分的深层液压系统的重大结构变化，而这又可以通过 MT 检测到。在这里，我们提出了一项实验，通过 MT 站网络对整个活动板块边界进行成像，从太平洋到大峡谷，穿过乔拉梅附近 SAF 下方的 NVT 区域。这些结果对于 SAFOD 的现场表征非常重要，因为导电结构的沿走向变化可能反映了控制 SAF 仍存在争议的机械状态的深层结构变化。