Holocene Seismicity of the Northern San Andreas Fault Based on Precise Dating of the Turbidite Event Record

基于浊积事件记录精确测年的圣安德烈亚斯断层北部全新世地震活动

• 批准号: 0440427
• 负责人: Chris Goldfinger
• 金额: --
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440427&HistoricalAwards=false
• 关键词: Holocene; Seismicity; Northern; San; Andreas

The Northern San Andreas Fault last ruptured in the great 1906 earthquake that destroyed San Francisco. Efforts on land to determine the frequency of such earthquake and their magnitudes and rupture lengths have been hampered by few suitable localities where a geologic record has been created. Offshore, new core data show that continental margin channels in Northern California have recorded a Holocene history of regional submarine landslides possibly triggered by San Andreas great earthquakes. This project is applying marine paleoseismologic techniques to the turbidite history along the Northern San Andreas transform margin using cores collected in 2002 during a cruise of the Scripps vessel R/V Roger Revelle.The goals of this project are to test models of full margin and segmented rupture along the North Coast segment of the San Andreas Fault. A Holocene event chronology along the margin from San Francisco to Cape Mendocino is being established using offshore turbidites and turbidite events are being tested for synchronous (and therefore earthquake) triggering. The methods include direct dating of each turbidite, biostratigraphy, and direct physical property correlation using density, magnetics, mineralogy and visible and X-ray imagery to construct a stratigraphic framework along the margin.Correlation of events between separate sites along the fault using radiocarbon, and fingerprints of each event are being used to test the linkages between deposits along the fault. Direct linkages point to an earthquake origin, since other triggers of submarine landslides happen in only one canyon at a time. Using this information, it may be possible to establish both rupture length and timing of past earthquakes along the Northern San Andreas. This information will be valuable for analysis of seismic hazards in San Francisco, as well as shed light on the long-term behavior of large fault systems that does not presently exist.

北圣安德烈亚斯断层上一次破裂是在1906年摧毁旧金山的大地震中。在陆地上确定此类地震的频率、震级和破裂长度的努力，由于很少有合适的地方有地质记录，因而受到阻碍。在海上，新的岩心数据显示，北加州大陆边缘的水道记录了一个全新世的区域性海底滑坡历史，可能是由圣安德烈亚斯大地震引发的。该项目将海洋古地震学技术应用于北圣安德烈亚斯转换边缘的浊积岩历史，使用2002年Scripps船R/V Roger Revelle巡航期间收集的岩心。该项目的目标是测试沿圣安德烈亚斯断层北海岸段的全边缘和分段破裂模型。从旧金山到门多西诺角边缘的全新世事件年表正在利用近海浊积岩建立，浊积岩事件正在进行同步触发（因此是地震）的测试。方法包括对每个浊积岩进行直接测年、生物地层学和直接物性对比，利用密度、磁学、矿物学、可见光和x射线成像来构建沿边缘的地层格架。利用放射性碳对断层沿线不同地点之间的事件进行相关性分析，并利用每个事件的指纹来测试断层沿线沉积物之间的联系。直接联系指向地震的起源，因为海底滑坡的其他触发因素一次只发生在一个峡谷中。利用这些信息，有可能确定北圣安德烈亚斯地震的破裂长度和时间。这些信息对于分析旧金山的地震危险是有价值的，同时也揭示了目前尚不存在的大型断层系统的长期行为。