Helium and Carbon Isotope Studies of Geothermal Fluids Along the North Anatolian Fault and Relationships to Seismicity

目前的建议旨在了解地球化学示踪剂（如氦和二氧化碳）与土耳其北安那托利亚断裂带（NAFZ）地震活动之间的关系。在与土耳其同事的合作下，他们正在监测主要元素和少量元素的地球化学以及其他同位素系统（18O， D/H和氚），我们计划从之前监测过的9个地热地点（来自生产井和地面泉）中取样，这些地点位于NAFZ 800公里的活动段。这两种地热示踪剂在区分地壳和地幔对挥发性储量的输入方面具有很大的效用。我们想要验证一个假设——在其他地震易发地区的研究中看到的——地幔和地壳衍生挥发物之间平衡的变化有可能成为阻碍地震活动的前兆。1999年，NAFZ地区的西部经历了两次灾难性的地震，造成超过25,000人死亡：它仍然是地震活跃的地区。这项研究旨在了解地壳流体对地震事件的反应，具有明确的社会意义。此外，通过与土耳其同事合作开展的前期工作发现，地幔衍生的3He存在于NAFZ西部活动区整个走向（约800公里）的流体中。幔源流体成分的存在表明在发震区的延脆过渡区有泄漏。对加州的圣安德烈亚斯断层系统（SAFS）也进行了同样的观察。事实上，NAFZ和SAFS之间还有许多其他相似之处。在本研究中获得的信息，特别是关于沿NAFZ的地震活动分布和震中向西移动（朝向伊斯坦布尔大都市）的信息，可能适用于SAFZ。

HiltonEAR-0229508The present proposal is aimed at understanding relationships between geochemical tracers such as helium and carbon dioxide and the occurrence of seismicity along the North Anatolian Fault Zone (NAFZ) in Turkey. In collaboration with Turkish colleagues, who are monitoring major and minor element geochemistry and other isotope systems (18O, D/H and tritium), we plan to sample fluids for helium and carbon (from production wells and surface springs) from nine previously-monitored geothermal localities sited along an 800-km active segment of the NAFZ. These two geothermal tracers have great utility in their ability to distinguish crustal and mantle inputs to the volatile inventory. We want to test the hypothesis - seen in other studies of earthquake-prone regions - that changes in the balance between mantle- and crustal-derived volatiles have potential as a precursor of impeding seismic activity. The western segment of the NAFZ region experienced two catastrophic earthquakes in 1999 entailing more than 25,000 fatalities: it continues to be seismically active. This work, aimed at understanding how crustal fluids respond to seismic events, has clear societal relevance. In addition, prior work carried out through collaborative efforts with our Turkish colleagues has discovered that mantle-derived 3He occurs in fluids along the entire strike (~800 km) of the active western segment of the NAFZ. The presence of a mantle-derived fluid component indicates leakage across the ductile-brittle transition region of the seismogenic zone. The same observation has been made for the San Andreas Fault System (SAFS) in California. Indeed there are many other parallels between the NAFZ and the SAFS. Information gained in the present study, particularly on the distribution of seismicity along the NAFZ and the westward progression of epicenters (towards the metropolis of Istanbul), may be applicable to the SAFZ.